The increasing frequency and severity of High Nighttime Temperature (HNT) threatens to damage rice quality by inducing the chalky grain phenotype. To better understand the roles that small RNAs (sRNAs) play in HNT-induced chalkiness in rice, we sequenced sRNA libraries from the R6-stage caryopses samples and flag leaves of 8 rice genotypes differing in their HNT-induced chalkiness (low chalky [LC] or high chalky [HC]) under Control Nighttime Temperature (CNT) and HNT conditions. These efforts allowed us to deposit 84 high-quality sRNA libraries for 8 varieties. Additionally, high-quality degradome libraries were generated for the caryopses and flag leaves of the Cypress variety under both CNT and HNT conditions. Our sRNA sequencing data is likely to be useful in detecting potential relationships between sRNA regulation and the HNT-induced chalky phenotype, while the degradome sequencing data will be useful in identifying sRNA targets relevant to the tissues and conditions analysed. Both the sRNA and degradome sequencing libraries have been deposited in the Sequence Read Archive, so they can be further analysed in future studies investigating the importance of HNT-altered sRNAs not only on grain quality, but also for many other important agronomic traits.

Background : Higher ambient temperatures during the cropping season, especially during nighttime, reduces rice grain quality by increasing chalkiness, primarily defined by altered starch metabolism. MicroRNAs (miRNAs) regulate various biological processes, including grain development and maturation. However, their role in high nighttime temperature (HNT)-induced grain chalkiness in rice is unknown. To address this phenomenon, an attempt was made to identify HNT-responsive miRNAs in developing caryopses and flag leaves. The miRNA expression levels were investigated between several high chalky (HC) and low chalky (LC) varieties to identify potential microRNAs involved in impacting grain chalkiness traits. Results : 138 small RNA-seq libraries were generated from the R6-stage caryopses and flag leaves from a panel of 13 rice varieties with varying chalkiness under HNT. Genetic variation among rice varieties for miRNAs expression was found. A comparison of miRNAs for differential regulation patterns between genetically closely related HC and LC varieties revealed specific miRNAs with consistently higher expression levels in one phenotype relative to the other. Notably, some of these miRNAs have predicted or confirmed effects in regulating grain quality and HNT responses. Furthermore, a degradome analysis of mRNA in caryopsis and flag leaf tissues revealed several novel miRNA-mRNA target pairs with some targets possibly involved in rice starch metabolism. Conclusions : This study revealed a number of differentially regulated miRNAs with potential roles towards alterations of grain chalkiness in rice under HNT stress. These miRNAs are potential candidates for future analyses and investigation regarding their effects on improving rice grain quality under HNT-stress conditions in field settings.

Red blotch disease, caused by Grapevine red blotch virus (GRBV, genus Grablovirus, family Geminiviridae), negatively impacts vine health, fruit yield, and quality, leading to substantial economic losses to growers. While recent studies have enhanced our understanding of the epidemiology of GRBV and its effects, little is known about the molecular basis of the host-virus interactions. Since small RNAs (sRNAs) are known to play a central role in host-virus interactions, this study was undertaken to investigate sRNA dynamics in leaves and berries at two phenological stages (asymptomatic pre- and symptomatic post-véraison) of GRBV-infected grapevines (Vitis vinifera cv. Merlot). Among the 140 microRNAs (miRNAs) detected, 41 isoforms belonging to 18 miRNA families exhibited significant differential expression in response to GRBV infection. Furthermore, 50 miRNAs showed differential expression in samples from pre- and post-véraison stages. A total of 58 conserved and 41 novel targets for known V. vinifera miRNAs were validated using degradome sequencing data from leaf samples of pre- and post-véraison stages. Additionally, virus-derived siRNAs (vsiRNAs) specific to GRBV were present only in GRBV-positive samples. The vsiRNAs predominantly ranged from 19 to 24 nucleotides (nt), with the 21nt size being the most abundant. Mapping vsiRNAs across the GRBV genome revealed an uneven distribution, with vsiRNA-generating hotspots predominantly located in the V3 ORF. Of the 83 most abundant vsiRNAs, grapevine target transcripts were identified for eight of them. Identification of differentially expressed miRNAs and vsiRNAs, as well as their targets, offered important insights into various pathways and mechanisms that were affected in grapevine infected with GRBV and in modulating different host responses in leaves and berries. This research serves as a foundation for a better understanding of the molecular interactions in this plant-geminivirus pathosystem.

Among many mRNA modifications, adenine methylation at the N-6 position (N-6-methyladenosine, m6A) is known to affect mRNA biology extensively. The influence of m6A has yet to be assessed under drought, one of the most impactful abiotic stresses. We show that Arabidopsis thaliana (L.) Heynh. (Arabidopsis) plants lacking mRNA ADENOSINE METHYLASE (MTA) are drought-sensitive. Subsequently, we comprehensively assess the impacts of MTA-dependent m(6)A changes during drought on mRNA abundance, stability, and translation in Arabidopsis. During drought, there is a global trend toward hypermethylation of many protein-coding transcripts that does not occur in mta. We also observe complex regulation of m6A at a transcript-specific level, possibly reflecting compensation by other m(6)A components. Importantly, a subset of transcripts that are hypermethylated in an MTA-dependent manner exhibited reduced turnover and translation in mta, compared with wild-type (WT) plants, during drought. Additionally, MTA impacts transcript stability and translation independently of m(6)A. We also correlate drought-associated deposition of m6A with increased translation of modulators of drought response, such as RD29A, COR47, COR413, ALDH2B, ERD7, and ABF4 in WT, which is impaired in mta. m(6)A is dynamic during drought and, alongside MTA, promotes tolerance by regulating drought-responsive changes in transcript turnover and translation.

Recently, post-transcriptional regulation of mRNA mediated by N6-methyladenosine (m6A) has been found to have profound effects on transcriptome regulation during plant responses to various abiotic stresses. However, whether this RNA modification can affect an oxidative stress response in plants has not been studied. To assess the role of m6A modifications during copper-induced oxidative stress responses, m6A-IP-seq was performed in Arabidopsis seedlings exposed to high levels of copper sulfate. This analysis revealed large-scale shifts in this modification on the transcripts most relevant for oxidative stress. This altered epitranscriptomic mark is known to influence transcript abundance and translation; therefore we scrutinized these possibilities. We found an increased abundance of copper-enriched m6A-containing transcripts. Similarly, we also found increased ribosome occupancy of copper-enriched m6A-containing transcripts, specifically those encoding proteins involved with stress responses relevant to oxidative stressors. Furthermore, the significance of the m6A epitranscriptome on plant oxidative stress tolerance was uncovered by assessing germination and seedling development of the mta (N6-methyladenosine RNA methyltransferase A mutant complemented with ABI3:MTA) mutant exposed to high copper treatment. These analyses suggested hypersensitivity of the mta mutant compared to the wild-type plants in response to copper-induced oxidative stress. Overall, our findings suggest an important role for m6A in the oxidative stress response of Arabidopsis.

High temperature impairs starch biosynthesis in developing rice grains and thereby increases chalkiness, affecting the grain quality. Genome encoded microRNAs (miRNAs) fine-tune target transcript abundances in a spatio-temporal specific manner, and this mode of gene regulation is critical for a myriad of developmental processes as well as stress responses. However, the role of miRNAs in maintaining rice grain quality/chalkiness during high daytime temperature (HDT) stress is relatively unknown. To uncover the role of miRNAs in this process, we used five contrasting rice genotypes (low chalky lines Cyp, Ben, and KB and high chalky lines LaGrue and NB) and compared the miRNA profiles in the R6 stage caryopsis samples from plants subjected to prolonged HDT (from the onset of fertilization through R6 stage of caryopsis development). Our small RNA analysis has identified approximately 744 miRNAs that can be grouped into 291 families. Of these, 186 miRNAs belonging to 103 families are differentially regulated under HDT. Only two miRNAs, Osa-miR444f and Osa-miR1866-5p, were upregulated in all genotypes, implying that the regulations greatly varied between the genotypes. Furthermore, not even a single miRNA was commonly up/down regulated specifically in the three tolerant genotypes. However, three miRNAs (Osa-miR1866-3p, Osa-miR5150-3p and canH-miR9774a,b-3p) were commonly upregulated and onemiRNA (Osa-miR393b-5p) was commonly downregulated specifically in the sensitive genotypes (LaGrue and NB). These observations suggest that few similarities exist within the low chalky or high chalky genotypes, possibly due to high genetic variation. Among the five genotypes used, Cypress and LaGrue are genetically closely related, but exhibit contrasting chalkiness under HDT, and thus, a comparison between them is most relevant. This comparison revealed a general tendency for Cypress to display miRNA regulations that could decrease chalkiness under HDT compared with LaGrue. This study suggests that miRNAs could play an important role in maintaining grain quality in HDT-stressed rice.

N6-methyladenosine (m6A) modification is essential for plant growth and development. Exploring m6A methylation patterns in rice tissues is fundamental to understanding the regulatory effects of this modification. Here, we profiled the transcriptome-wide m6A landscapes of rice panicles at the booting stage (PB) and flowering stage (PF), and of flag leaves at the flowering stage (LF). The global m6A level differed significantly among the three tissues and was closely associated with the expression of writer and eraser genes. The methylated gene ratio was higher in the flag leaves than in the panicles. Compared with commonly methylated genes, tissue-specific methylated genes showed lower levels of both m6A modification and expression, and a preference for m6A deposition in the coding sequence region. The m6A profiles of the two organs had more distinct differences than the profiles of the same organ at different stages. A negative correlation between m6A levels and gene expression was observed in PF vs. PB but not in PF vs. LF, indicting the complicated regulatory effect of m6A on gene expression. The distinct expression patterns of m6A reader genes in different tissues indicate that readers may affect gene stability through binding. Overall, our findings demonstrated that m6A modification influences tissue function by regulating gene expression. Our findings provide valuable insights on the regulation and biological functions of m6A modifications in rice.

Coreopsis lanceolata, known as lance-leaf coreopsis, is a perennial plant with high ornamental value. It is widely grown in many public parks and home gardens in China due to its showy flowers. From May to June 2020, typical powdery mildew-signs and symptoms were seen on leaves of C. lanceolata cultivated in the east campus of Henan Normal University, Henan Province, China. Abundant white powder-like masses in spot- or coalesced-lesions were on ad- and abaxial surfaces of plant leaves and covered up to 50 % of the leaf area. The infected leaves were deformed and eventually prematurely senescent. Approximately 80 % of observed C. lanceolata plants showed these signs and symptoms. Unbranched conidiophores (n = 25) were 90 to 200 × 12 to 20 μm and showed a foot cell, followed by 1 to 3 short cells and conidia. Ellipsoid-ovoid shaped conidia (n = 30) were 22 to 36 × 15 to 23 μm, with a length/width ratio of 1.4 to 2.4. No chasmothecia were detected. The powdery mildew fungus was initially identified as Podosphaera fusca based on the morphological characteristics. Total genomic DNA of the pathogen was extracted and the rDNA internal transcribed spacer (ITS) region was amplified and sequenced using the primers ITS1/ITS4 (White et al. 1990; Zhu et al. 2019). The obtained sequence was deposited into GenBank under Accession No. MT899186 and was 100 % identical to P. fusca (JX546297) from Herba eupatorii (Ding et al. 2013). To perform pathogenicity assays, leaf surface of three healthy plants was inoculated with fungal conidia according to a previously described method (Zhu et al. 2021). As a control, three non-inoculated plants were used. The control and inoculated plants were placed separately in two growth chambers (light/dark, 16 h/8 h; humidity, 65 %; temperature, 20 ℃). Fourteen- to sixteen-days post inoculation, powdery mildew signs were noticed on inoculated plants, whereas control remained asymptomatic. Similar results were found by performing two repeated pathogenicity assays. Therefore, based on the morphological and molecular analysis, the pathogen was identified and confirmed as P. fusca. This fungus has been reported on C. lanceolata in Korea (Park et al. 2010) and Italy (Garibaldi et al. 2007). This is, to the best of our knowledge, the first report of P. fusca on C. lanceolata in China. The sudden occurrence of this powdery mildew disease on C. lanceolata may adversely affect the health of valuable ornamentals in China. The precise identification of the causal agent of this powdery mildew of C. lanceolata is a preliminary step in developing effective disease management strategies.

Highlights: • m6A is spatiotemporally regulated and closely related to rice development.• Common and tissue-specific methylation have shown distinct features.• Effect of m6A modification on gene expression is complicated.

Simplicillium spp. are mycoparasites that exert growth-inhibitory effects on phytopathogenic fungi. However, limited studies have examined the effects of Simplicillium spp . on powdery mildews. In this study, morphological and molecular analyses revealed that S. aogashimaense is a mycoparasite of the wheat powdery mildew fungus, Blumeria graminis f. sp. tritici ( Bgt ), under field conditions. The inoculation of Bgt colonies with S. aogashimaense significantly impaired Bgt colony formation and conidial distribution and markedly decreased the biomass of Bgt . To examine the interaction between Simplicillium and Bgt , an S. aogashimaense strain that constitutively expresses green fluorescent protein (GFP) was constructed using the Agrobacterium tumefaciens -mediated transformation (ATMT) method. The hyphae of GFP-expressing S. aogashimaense directly penetrated the B. graminis structures. These findings indicate that ATMT can be employed to reveal the biocontrol activities of physiologically and phylogenetically diverse Simplicillium spp. In vitro, S. aogashimaense exudates compromised Bgt conidial germination and appressorial formation. Thus, S. aogashimaense functions as a potential biological control agent by impeding the development of Bgt and can be a viable alternative for controlling the wheat powdery mildew. To gain further insights into the mechanism underlying this mycoparasitism, the genome of S. aogashimaense was sequenced and assembled. S. aogashimaense harbored seven chromosomes comprising 8963 protein-coding genes. Additionally, two putative effector-coding genes ( Sao008714 and Sao006491 ) were identified. The expression levels of Sao008714 and Sao006491 in S. aogashimaense were dramatically upregulated during the mycoparasitic interaction. In addition, 41 gene clusters putatively involved in the production of secondary metabolites, which exhibit insecticidal, antifungal and antibacterial activities, were identified using genome-wide identification, annotation and analysis of secondary metabolite biosynthesis gene clusters. These results suggest that S. aogashimaense parasitizes Bgt and hence, can be considered for phytopathogen management.

SUMMARY Plants respond to low temperatures by altering the mRNA abundance of thousands of genes contributing to numerous physiological and metabolic processes that allow them to adapt. At the post‐transcriptional level, these cold stress‐responsive transcripts undergo alternative splicing, microRNA‐mediated regulation and alternative polyadenylation, amongst others. Recently, m6A, m5C and other mRNA modifications that can affect the regulation and stability of RNA were discovered, thus revealing another layer of post‐transcriptional regulation that plays an important role in modulating gene expression. The importance of m6A in plant growth and development has been appreciated, although its significance under stress conditions is still underexplored. To assess the role of m6A modifications during cold stress responses, methylated RNA immunoprecipitation sequencing was performed in Arabidopsis seedlings esposed to low temperature stress (4°C) for 24 h. This transcriptome‐wide m6A analysis revealed large‐scale shifts in this modification in response to low temperature stress. Because m6A is known to affect transcript stability/degradation and translation, we investigated these possibilities. Interestingly, we found that cold‐enriched m6A‐containing transcripts demonstrated the largest increases in transcript abundance coupled with increased ribosome occupancy under cold stress. The significance of the m6A epitranscriptome on plant cold tolerance was further assessed using the mta mutant in which the major m6A methyltransferase gene was mutated. Compared to the wild‐type, along with the differences in CBFs and COR gene expression levels, the mta mutant exhibited hypersensitivity to cold treatment as determined by primary root growth, biomass, and reactive oxygen species accumulation. Furthermore, and most importantly, both non‐acclimated and cold‐acclimated mta mutant demonstrated hypersensitivity to freezing tolerance. Taken together, these findings suggest a critical role for the epitranscriptome in cold tolerance of Arabidopsis.

RNA interference (RNAi) is one of the important mechanisms to regulate gene expression in eukaryotes. One of the original functions of RNAi is to facilitate the antiviral strategy of host. Early studies reveal that invertebrates can use RNAi to resist viruses. However, if this mechanism exists in mammals is still controversial. The latest studies confirm that mammals do have the RNAi-based immunity, and researchers believe that RNAi-based antiviral immunity is a brand-new immunological mechanism that was neglected in the past. It is worthy to note that virus can also use RNAi to enhance its infectivity and immune escape in host cells. This review introduces the research history of RNAi-based antiviral immunity in animals and summarizes the main findings in this field. Last but not least, we indicate a series of unresolved questions about RNAi-based antiviral immunity, and explore the relationship between RNAi-based antiviral immunity and other innate immunological pathways. The virus-mediated RNAi pathway in animal is not only an interesting basic biology question, but also has important guiding roles in the development of antiviral drugs.

Mepiquat chloride (MC) is the most important plant growth retardant that is widely used in cotton ( Gossypium hirsutum L.) production to suppress excessive vegetative growth and improve plant architecture. MicroRNAs (miRNAs) are important gene expression regulators that control plant growth and development. However, miRNA-mediated post-transcriptional regulation in MC-induced growth inhibition remains unclear. In this study, the dynamic expression profiles of miRNAs responsive to MC in cotton internodes were investigated. A total of 508 known miRNAs belonging to 197 families and five novel miRNAs were identified. Among them, 104 miRNAs were differentially expressed at 48, 72, or 96 h post MC treatment compared with the control (0 h); majority of them were highly conserved miRNAs. The number of differentially expressed miRNAs increased with time after treatment. The expression of 14 known miRNAs was continuously suppressed, whereas 12 known miRNAs and one novel miRNA were continuously induced by MC. The expression patterns of the nine differentially expressed miRNAs were verified using qRT-PCR. The targets of the known and novel miRNAs were predicted. Four conserved and six novel targets were validated using the RLM-5′ RACE assay. This study revealed that miRNAs play crucial regulatory roles in the MC-induced inhibition of internode elongation. It can improve our understanding of post-transcriptional gene regulation in MC-mediated growth inhibition and could potentially facilitate the breeding of dwarf cotton.

Background Winter wheat requires prolonged exposure to low temperature to initiate flowering (vernalization). Shoot apical meristem of the crown is the site of cold perception, which produces leaf primordia during vegetative growth before developing into floral primordia at the initiation of the reproductive phase. Although many essential genes for winter wheat cold acclimation and floral initiation have been revealed, the importance of microRNA (miRNA) meditated post-transcriptional regulation in crowns is not well understood. To understand the potential roles of miRNAs in crown tissues, we performed a temporal expression study of miRNAs in crown tissues at the three-leaf stage, winter dormancy stage, spring green-up stage, and jointing stage of winter wheat grown under natural growth conditions. Results In total, 348 miRNAs belonging to 298 miRNA families, were identified in wheat crown tissues. Among them, 92 differentially expressed miRNAs (DEMs) were found to be significantly regulated from the three-leaf stage to the jointing stage. Most of these DEMs were highly expressed at the three-leaf stage and winter dormancy stage, and then declined in later stages. Six DEMs, including miR156a-5p were markedly induced during the winter dormancy stage. Eleven DEMs, including miR159a.1, miR390a-5p, miR393-5p, miR160a-5p, and miR1436, were highly expressed at the green-up stage. Twelve DEMs, such as miR172a-5p, miR394a, miR319b-3p, and miR9676-5p were highly induced at the jointing stage. Moreover, 14 novel target genes of nine wheat or Pooideae-specific miRNAs were verified using RLM-5 ' RACE assay. Notably, six mTERFs and two Rf1 genes, which are associated with mitochondrial gene expression, were confirmed as targets of three wheat-specific miRNAs. Conclusions The present study not only confirmed the known miRNAs associated with phase transition and floral development, but also identified a number of wheat or Pooideae-specific miRNAs critical for winter wheat cold acclimation and floral development. Most importantly, this study provided experimental evidence that miRNA could regulate mitochondrial gene expression by targeting mTERF and Rf1 genes. Our study provides valuable information for further exploration of the mechanism of miRNA mediated post-transcriptional regulation during winter wheat vernalization and inflorescent initiation.

The superoxide dismutases (SODs) play vital roles in controlling cellular reactive oxygen species (ROS) that are generated both under optimal as well as stress conditions in plants. The rice genome harbors seven SOD genes (CSD1, CSD2, CSD3, CSD4, FSD1, FSD2, and MSD) that encode seven constitutive transcripts. Of these, five (CSD2, CSD3, CSD4, FSD1, and MSD) utilizes an alternative splicing (AS) strategy and generate seven additional splice variants (SVs) or mRNA variants, i.e., three for CSD3, and one each for CSD2, CSD4, FSD1, and MSD. The exon-intron organization of these SVs revealed variations in the number and length of exons and/or untranslated regions (UTRs). We determined the expression patterns of SVs along with their constitutive forms of SODs in rice seedlings exposed to salt, osmotic, cold, heavy metal (Cu+2) stresses, as well as copper-deprivation. The results revealed that all seven SVs were transcriptionally active in both roots and shoots. When compared to their corresponding constitutive transcripts, the profiles of five SVs were almost similar, while two specific SVs (CSD3-SV4 and MSD-SV2) differed significantly, and the differences were also apparent between shoots and roots suggesting that the specific SVs are likely to play important roles in a tissue-specific and stress-specific manner. Overall, the present study has provided a comprehensive analysis of the SVs of SODs and their responses to stress conditions in shoots and roots of rice seedlings.

Sorghum is largely grown for food, fodder and for biofuel production in semi-arid regions where the drought or high temperature or their combination co-occur. Plant microRNAs (miRNAs) are integral to the gene regulatory networks that control almost all biological processes including adaptation to stress conditions. Thus far, plant miRNA profiles under separate drought or heat stresses have been reported but not under combined drought and heat. In this study, we report miRNA profiles in leaves of sorghum exposed to individual drought or heat or their combination. Approximately 29 conserved miRNA families represented by 80 individual miRNAs, 26 families represented by 47 members of less conserved or sorghum-specific miRNA families as well as 8 novel miRNA families have been identified. Of these, 25 miRNAs were found to be differentially regulated in response to stress treatments. The comparative profiling revealed that the miRNA regulation was stronger under heat or combination of heat and drought compared to the drought alone. Furthermore, using degradome sequencing, 48 genes were confirmed as targets for the miRNAs in sorghum. Overall, this study provides a framework for understanding of the miRNA-guided gene regulations under combined stresses.

Bromus catharticus, rescuegrass, is a brome grass that has been cultivated for herbage production, and been widely naturalized in many provinces of China, including Henan province. During April and May 2020, powdery mildew was found on leaves of Br. catharticus on the campus of Henan Normal University, Xinxiang city (35.3°N; 113.9°E), Henan Province, China. Abundant white or grayish irregular or coalesced circular powdery colonies were scattered on the adaxial surface of leaves and 70% of the leaf areas were affected. Some of the infected leaves either were chlorotic or senescent. About 60% of the observed plants showed powdery mildew symptoms. Conidiophores (n = 25) were 32 to 45 μm × 7 to 15 μm and composed of foot cells and conidia (mostly 6 conidia) in chains. Conidia (n = 50) were 25 to 35 μm × 10 to 15 μm, on average 30 × 13 μm, with a length/width ratio of 2.3. Chasmothecia were not found. Based on these morphologic characteristics, the pathogen was initially identified as Blumeria graminis f. sp. bromi (Braun and Cook 2012; Troch et al. 2014). B. graminis mycelia and conidia were collected, and total genomic DNA was extracted (Zhu et al. 2019). The rDNA internal transcribed spacer (ITS) region was amplified with primer pairs ITS1/ITS4. The amplicon was cloned and sequenced. The sequence (574 bp) was deposited into GenBank under Accession No. MT892940. BLASTn analysis revealed that MT892940 was 100% identical to B. graminis f. sp. bromi on Br. catharticus (AB000935, 550 of 550 nucleotides) (Takamatsu et al. 1998). Phylogenetic analysis of MT892940 and ITS of other B. graminis ff. spp. clearly indicated least two phylogenetically distinct clades of B. graminis f. sp. bromi and that MT892940 clustered with the Takamatsu vouchers. Leaf surfaces of five healthy plants were fixed at the base of a settling tower and then inoculated by blowing conidia from diseased leaves using pressurized air. Five non-inoculated plants served as controls. The inoculated and non-inoculated plants were maintained separately in two growth chambers (humidity, 60%; light/dark, 16 h/8 h; temperature, 18℃). Thirteen- to fifteen-days after inoculation, B. graminis signs and symptoms were visible on inoculated leaves, whereas control plants remained asymptomatic. The pathogenicity assays were repeated twice with the same results. The observed signs and symptoms were morphologically identical to those of the originally infected leaves. Accordingly, the causal organism of the powdery mildew was confirmed as B. graminis f. sp. bromi by morphological characteristics and ITS sequence data. B. graminis has been reported on Br. catharticus in the United States (Klingeman et al. 2018), Japan (Inuma et al. 2007) and Argentina (Delhey et al. 2003). To our best knowledge, this is the first report of B. graminis on Br. catharticus in China. Since hybridization of B. graminis ff. spp. is a mechanism of adaptation to new hosts, Br. catharticus may serve as a primary inoculum reservoir of B. graminis to infect other species (Menardo et al. 2016). This report provides fundamental information for the powdery mildew that can be used to develop control management of the disease in Br. catharticus herbage production.

The plant growth retardant mepiquat chloride (MC) has been extensively used to produce compact plant canopies and increase yield in cotton (Gossypium hirsutum L.). Previous studies showed that MC reduced plant height and internode length by inhibiting GA biosynthesis and cell elongation. However, whether there are other molecular mechanisms underlying MC-induced growth retardation has remained largely unknown. In the present study, we conducted histological, transcriptomic, and phytohormone analyses of the second elongating internodes of cotton seedlings treated with MC. Histological analysis revealed that the MC shortened the internodes through suppressing both cell division and cell elongation. Consistent with the observed phenotype, many genes related to cell growth were significantly downregulated by MC. Transcriptome profiling showed that the expression of genes related not only to GA, but also to auxin, brassinosteroid (BR), and ethylene metabolism and signaling was remarkably suppressed, whereas that of genes related to cytokinin (CK) and abscisic acid (ABA) metabolism was induced by MC. Consistent with the expression pattern, significant decrease of endogenous GA, auxin, and BR content, but an increase in CK content was observed after MC treatment. Most of these hormone related genes displayed opposite regulation pattern by exogenous GA3 treatment compared to MC; simultaneous application of MC and GA3 could alleviate the genes expression changes induced by MC treatment, indicating MC does not directly affect other plant hormones, but through the inhibition of the GA biosynthesis. In addition, the expression of genes related to secondary metabolism and many transcription factors (TFs) were differentially regulated by MC. In summary, we confirmed the important role of GA in MC-induced growth inhibition of cotton, and further found that other hormones were also involved in this process in a GA-dependent manner. This study provides novel insights into the molecular mechanism underlying the MC-mediated inhibition of internode elongation in cotton seedlings.

The cuticle of citrus is known to modulate fruit postharvest quality and is hypothesized to be involved in resistance against the fungal pathogen, Penicillium digitatum. However, only scarce information is available on the effect of cuticular wax on the conidial germination, germ tube elongation, and colony development of P. digitatum. Utilizing a versatile Formvar(R)-based in vitro system, we were able to assess the development of P. digitatum in the absence of secondary effects of its host. In vivo and in vitro, we found that the cuticular wax of mandarin (Citrus reticulata) fruit impaired P. digitatum colony expansion. Compared with the colony size of P. digitatum on intact fruit, the area of colonies on fruit supplemented with mandarin cuticular wax decreased significantly by 1.7 times, whereas it increased 1.6 times on dewaxed fruit 72 h post inoculation. Similar results were observed at 96 h post inoculation. Thus, the cuticular wax of mandarin fruit, acting as a physical barrier, impairs the colony expansion of P. digitatum, making it a viable alternative for citrus fruit coating that effectively controls green mold colony formation during postharvest storage. Interestingly, in vitro cuticular wax of mandarin fruit dramatically stimulated conidial germination and germ tube elongation of this pathogen. These results suggest that the cuticular wax might be the chemical cue for P. digitatum during host-recognition processes. Overall, our results suggest that the cuticular wax of mandarin fruit plays meaningful roles in the interaction between the citrus fruit and P. digitatum, and hence, can be considered for postharvest disease management.