Maize (Zea mays L.) is an important cereal crop worldwide, but production is constrained by salt stress, which disrupts plant cell nutrient metabolism, leading to diminished growth and yield. Therefore, the mining of salt-tolerance genes and breeding of new salt-tolerant germplasm is crucial for improvement of maize yield. In this study, ZmWRKY17 (Zm00001d004086) overexpression and mutant lines were exposed to 250-mM and 300-mM NaCl, respectively, for 7 days. Exposed to salt stress, the overexpression lines produced significantly more malondialdehyde and hydrogen peroxide than the control line, accompanied by an increased rate of superoxide anion production and relative electrolyte leakage. The mutant line had a higher percentage survival, higher leaf relative water content, and lower cellular damage under extreme salt stress. According to these findings, ZmWRKY17 appears to have a negative regulatory effect on maize salt tolerance. In addition, under salt stress, ZmWRKY17 overexpression plants accumulated more abscisic acid (ABA) than the control plants. The root of ZmWRKY17 overexpression plants showed reduced sensitivity to ABA. Based on the results of transcriptome analysis, two candidate genes, Zm00001d016105 (ZmPYL10) and Zm00001d016294 (ZmPYL3), were screened for regulation by ZmWRKY17. The dual-luciferase experiments demonstrated that ZmWRKY17 binds to the promoter regions of ZmPYL10 and ZmPYL3, thereby regulating the expression of downstream genes. In conclusion, this study indicates that ZmWRKY17 is involved in regulating the expression of ABA receptor genes ZmPYL10 and ZmPYL3 to reduce the sensitivity of plants to ABA and, ultimately, negatively regulate plant salt tolerance.

This chapter outlines detailed methods and protocols for studying the structure and mechanisms of abscission layers (ALs) in rice. Utilizing rice spikelets as a primary example, these protocols provide comprehensive techniques for analyzing AL development, including tissue preparation, microscopy, and histochemical assays. The AL is a specialized tissue where cell separation takes place, and it is crucial for processes such as organ shedding and fruit drop. By examining the AL, researchers can uncover the physiological and genetic factors governing plant organ separation. These insights are pertinent for advancing agricultural practices and crop improvement, as understanding the dynamics of the AL can lead to the development of rice varieties with enhanced traits related to abscission and grain retention. These improvements can result in better yield stability and reduced post-harvest losses, which are essential for meeting the food demands of a growing global population. By focusing on the genetic and physiological mechanisms governing the AL, researchers can develop innovative strategies to optimize rice production and contribute to food security.

Plant height is an important agronomic characteristic of rice ( Oryza sativa L. ). Map-based cloning analyses of a natural semi-dwarf rice mutant with inwardly curled leaves found in the field revealed that the defects were due to a mutation of a SHAQKYF-class MYB family transcription factor, OsKANADI1 (OsKAN1). OsKAN1 directly bound to the OsYABBY5 ( OsYAB5 ) promoter to repress its expression and interacted with OsYAB5 to form a functional OsKAN1-OsYAB5 complex. GIBERELLIN 2-OXIDASE6 ( OsGA2ox6 ), encoding an enzyme in the gibberellin (GA) catabolic pathway, was activated by OsYAB5. Furthermore, the OsKAN1-OsYAB5 complex suppressed the inhibitory effect of OsKAN1 toward OsYAB5 and inhibited OsYAB5-induced OsGA2ox6 expression. The proOsKAN1: OsYAB5 transgenic plants were taller than wild-type plants, whereas oskan1 proOsKAN1:OsYAB5 plants exhibited a severe dwarf phenotype due to the absence of the OsKAN1-OsYAB5 complex. The OsKAN1-OsYAB5 complex modulated OsGA2ox6 expression, thereby regulating the levels of bioactive gibberellins and, consequently, plant height. This study elucidated the mechanism underlying the effect of the OsKAN1-OsYAB5-OsGA2ox6 regulatory pathway on plant height at different positions in rice stems and provided insights on stem development and candidate genes for the aerial architecture improvement of crop plants.

Low temperature causes rice yield losses of up to 30%–40%, therefore increasing its cold tolerance is a breeding target. Few genes in rice are reported to confer cold tolerance at both the vegetative and reproductive stages. This study revealed a rice-specific 24-nt miRNA, miR1868, whose accumulation was suppressed by cold stress. Knockdown of MIR1868 increased seedling survival, pollen fertility, seed setting, and grain yield under cold stress, whereas its overexpression conferred the opposite phenotype. Knockdown of MIR1868 increased reactive oxygen species (ROS) scavenging and soluble sugar content under cold stress by increasing the expression of peroxidase genes and sugar metabolism genes, and its overexpression produced the opposite effect. Thus, MIR1868 negatively regulated rice cold tolerance via ROS scavenging and sugar accumulation.

Human brain microvascular endothelial cells (hBMECs) are the main component cells of the blood-brain barrier (BBB) and play a crucial role in responding to viral infections to prevent the central nervous system (CNS) from viral invasion. Interferon-inducible transmembrane protein 1 (IFITM1) is a multifunctional membrane protein downstream of type-I interferon. In this study, we discovered that hIFITM1 expression was highly upregulated in hBMECs during Japanese encephalitis virus (JEV) infection. Depletion of hIFITM1 with CRISPR/Cas9 in hBMECs enhanced JEV replication, while overexpression of hIFITM1 restricted the viruses. Additionally, overexpression of hIFITM1 promoted the monolayer formation of hBMECs with a better integrity and a higher transendothelial electrical resistance (TEER), and reduced the penetration of JEV across the BBB. However, the function of hIFITM1 is governed by palmitoylation. Mutations of palmitoylation residues in conserved CD225 domain of hIFITM1 impaired its antiviral capacity. Moreover, mutants retained hIFITM1 in the cytoplasm and lessened its interaction with tight junction protein Occludin. Taken together, palmitoylation of hIFITM1 is essential for its antiviral activity in hBMECs, and more notably, for the maintenance of BBB homeostasis.

Seed shattering is an important trait that wild rice uses to adapt to the natural environment and maintain population reproduction, and weedy rice also uses it to compete with the rice crop. The loss of shattering is a key event in rice domestication. The degree of shattering is not only one of the main reasons for rice yield reduction but also affects its adaptability to modern mechanical harvesting methods. Therefore, it is important to cultivate rice varieties with a moderate shattering degree. In this paper, the research progress on rice seed shattering in recent years is reviewed, including the physiological basis, morphological and anatomical characteristics of rice seed shattering, inheritance and QTL/gene mapping of rice seed shattering, the molecular mechanism regulating rice seed shattering, the application of seed-shattering genes, and the relationship between seed-shattering genes and domestication.

The elimination of seed shattering was a key step in rice (Oryza sativa) domestication. In this paper, we show that increasing the gibberellic acid (GA) content or response in the abscission region enhanced seed shattering in rice. We demonstrate that SLENDER RICE1 (SLR1), the key repressor of GA signaling, could physically interact with the rice seed shattering-related transcription factors quantitative trait locus of seed shattering on chromosome 1 (qSH1), O. sativa HOMEOBOX 15 (OSH15), and SUPERNUMERARY BRACT (SNB). Importantly, these physical interactions interfered with the direct binding of these three regulators to the lignin biosynthesis gene 4-COUMARATE: COENZYME A LIGASE 3 (4CL3), thereby derepressing its expression. Derepression of 4CL3 led to increased lignin deposition in the abscission region, causing reduced rice seed shattering. Importantly, we also show that modulating GA content could alter the degree of seed shattering to increase harvest efficiency. Our results reveal that the "Green Revolution" phytohormone GA is important for regulating rice seed shattering, and we provide an applicable breeding strategy for high-efficiency rice harvesting.

C-repeat (CRT) binding factors (CBFs) are well known to act as crucial transcription factors that function in cold stress response. Arginine decarboxylase (ADC)- mediated putrescine (Put) biosynthesis has been reported to be activated in plants exposed to cold conditions, but it remains elusive whether CBFs can regulate ADC expression and Put accumulation. In this study, we show that cold upregulated ADC gene (Citrus sinensis ADC;CsADC) and elevated endogenous Put content in sweet orange (C.sinensis). The promoter of CsADC contains two CRT sequences that are canonical elements recognized by CBFs. Sweet orange genome contains four CBFs (CsCBF1-4), in which CsCBF1 was significantly induced by cold. CsCBF1, located in the nucleus, was demonstrated to bind directly and specifically to the promoter of CsADC and acted as a transcriptional activator. Overexpression of CsCBF1 led to notable elevation of CsADC and Put levels in sweet orange transgenic plants, along with remarkably enhanced cold tolerance, relative to the wild type. However, pretreatment with D-arginine, an ADC inhibitor, caused a prominent reduction of endogenous Put levels in the overexpressing lines, accompanied by greatly compromised cold tolerance. Taken together, these results demonstrate that the CBF1 of sweet orange directly regulates ADC expression and modulates Put synthesis for orchestrating the cold tolerance. Our findings shed light on the transcriptional regulation of Put accumulation through targeting the ADC gene in the presence of cold stress. Meanwhile, this study illustrates a new mechanism underlying the CBF-mediated cold stress response.

BackgroundCultivated soybean (Glycine max) is an important source for protein and oil. Each soybean strain has its own genetic diversity, and the availability of more soybean genomes may enhance comparative genomic analysis of soybean.ResultsIn this study, we constructed a high-quality de novo assembly of an elite soybean cultivar Jidou 17 (JD17) with high contiguity, completeness, and accuracy. We annotated 59,629 gene models and reconstructed 235,109 high-quality full-length transcripts. We have molecularly characterized the genotypes of some important agronomic traits of JD17 by taking advantage of these newly established genomic resources.ConclusionsWe reported a high-quality genome and annotations of a wide range of cultivars, and used them to analyze the genotypes of genes related to important agronomic traits of soybean in JD17. We have demonstrated that high-quality genome assembly can serve as a valuable reference for soybean genomics and breeding research community.

Copper-containing amine oxidases (CuAOs) play important roles in polyamine catabolism and function in plant development and abiotic stresses response. In this study, eight putative CuAO genes (CsCuAO1–CsCuAO8), distributed on three chromosomes, were identified in sweet orange (Citrus sinensis Osbeck) genome. They were divided into two major groups according to the phylogenetic analysis. The CsCuAOs possess typically conserved 33 amino acid residues and contain either a C-terminal peroxisomal targeting peptide or an N-terminal signal. Transcript levels of the CsCuAOs were detected in leaf, stem cotyledon, and root, but tissue-specific expression pattern was observed. Many putative cis-elements involved in hormone and stress response were predicted in a 1.5-kb promoter region of the CsCuAOs. The CsCuAOs were significantly induced by exogenous polyamines, including putrescine, spermidine, and spermine. ABA and various abiotic stresses (cold, salt, and osmotic shock) down-regulated most of the CsCuAOs, whereas CsCuAO3 and CsCuAO7 were up-regulated. Transient expression assay demonstrate that CsCuAO2 was involved in putrescine catabolism. Taken together, these findings provide valuable knowledge for better understanding of the potential biological functions of CuAO genes in polyamine catabolism of sweet orange.

Soil salinity, one of the major abiotic stresses limiting plant growth and productivity, affects large terrestrial areas of the world. Putrescine (Put), one of major Polyamines (PAs) widely present in organisms, is a type of low-molecular-weight aliphatic nitrogenous bases with function of regulating cell activities. Arginine decarboxylase (ADC) is a key rate-limiting enzyme in Put synthesis. It has been reported that loss-of-function mutant of the encoding gene AtADC2 is intolerant to salt stress in Arabidopsis. However, the effect of overexpression of AtADC2 on plant salt tolerance and the mechanisms about how ADC is involved in the response of plants to salt stress remain unknown. In this study, both overexpression lines of AtADC2 (AtADC2-OE), which has higher endogenous Put concentration, and loss-of-function mutant (adc2-3) were treated by salt stress. Under 150 mM NaCl stress condition, the growth of the mutant adc2-3 was more strongly inhibited than the wild type (Col-0). However, AtADC2-OE was less affected and displayed an enhanced salt tolerance. The chlorophyll content was detected to be significantly enhanced in AtADC2-OE lines and reduced in adc2-3 compared with in Col-0. These results indicated AtADC2-OE lines had more tolerance to salt stress. In addition, AtADC2 expression is up-regulated by salt stress in primary root tip of Arabidopsis seedling. Under salt stress, the contents of malonaldehyde, superoxide (O2.−) and hydrogen peroxide (H2O2), were increased in adc2-3, while H2O2 content was somewhat decreased in AtADC2-OE lines, as compared with those in Col-0. Determination of enzyme activities showed that after salt treatment, the activities of superoxide dismutase (SOD) and catalase (CAT) were enhanced significantly in AtADC2-OE lines, but varied inconspicuously in adc2-3. Taken together, our results reveal that, under salt stress, the increase in both expression of AtADC2 gene and Put accumulation regulates the activities of SOD and CAT to enhance the salt resistance of Arabidopsis thaliana.

Arginine decarboxylase (ADC)-mediated putrescine biosynthesis plays an important role in plant stress responses, but the transcriptional regulation of ADC in response to abiotic stress is not well understood. We isolated a NAM, ATAF1/2, and CUC (NAC) domain-containing transcription factor, PtrNAC72, from trifoliate orange (Poncirus trifoliata) by yeast one-hybrid screening. PtrNAC72, localized to the nucleus, binds specifically to the promoter of PtADC and acts as a transcriptional repressor. PtrNAC72 expression was induced by cold, drought, and abscisic acid. ADC messenger RNA abundance and putrescine levels were decreased in transgenic tobacco (Nicotiana nudicaulis) plants overexpressing PtrNAC72 but increased, compared with the wild type, in an Arabidopsis (Arabidopsis thaliana) transfer DNA insertion mutant, nac72 While transgenic tobacco lines overexpressing PtrNAC72 were more sensitive to drought, plants of the Arabidopsis nac72 mutant exhibited enhanced drought tolerance, consistent with the accumulation of reactive oxygen species in the tested genotypes. In addition, exogenous application of putrescine to the overexpression lines restored drought tolerance, while treatment with d-arginine, an ADC inhibitor, compromised the drought tolerance of nac72 Taken together, these results demonstrate that PtrNAC72 is a repressor of putrescine biosynthesis and may negatively regulate the drought stress response, at least in part, via the modulation of putrescine-associated reactive oxygen species homeostasis.

Plants are challenged by a variety of biotic or abiotic stresses, which can affect their growth and development, productivity and geographic distribution. In order to survive adverse environmental conditions, plants have evolved various adaptive strategies, among which is the accumulation of metabolites that play protective roles. A well-established example of the metabolites that are involved in stress responses, or stress tolerance, is the low-molecular-weight aliphatic polyamines, including putrescine,spermidine and spermine. The critical role of polyamines in stress tolerance is suggested by several lines of evidence: firstly, the transcript levels of polyamine biosynthetic genes, as well as the activities of the corresponding enzymes, are induced by stresses; secondly, elevation of endogenous polyamine levels by exogenous supply of polyamines, or overexpression of polyamine biosynthetic genes, results in enhanced stress tolerance; and thirdly, a reduction of endogenous polyamines is accompanied by compromised stress tolerance. A number of studies have demonstrated that polyamines function in stress tolerance largely by modulating the homeostasis of reactive oxygen species (ROS) due to their direct, or indirect, roles in regulating antioxidant systems or suppressing ROS production. The transcriptional regulation of polyamine synthesis by transcription factors is also reviewed here. Meanwhile, future perspectives on polyamine research are also suggested.

WRKY comprises a large family of transcription factors in plants, but most WRKY members are still poorly understood. In this study, we report functional characterization of a Group III WRKY gene (FcWRKY70) from Fortunella crassifolia. FcWRKY70 was greatly induced by drought and abscisic acid, but slightly or negligibly by salt and cold. Overexpression of FcWRKY70 in tobacco (Nicotiana nudicaulis) and lemon (Citrus lemon) conferred enhanced tolerance to dehydration and drought stresses. Transgenic tobacco and lemon exhibited higher expression levels of ADC (arginine decarboxylase), and accumulated larger amount of putrescine in comparison with wild type (WT). Treatment with D-arginine, an inhibitor of ADC, caused transgenic tobacco plants more sensitive to dehydration. Knock-down of FcWRKY70 in kumquat down-regulated ADC abundance and decreased putrescine level, accompanied by compromised dehydration tolerance. The promoter region of FcADC contained two W-box elements, which were shown to be interacted with FcWRKY70. Taken together, our data demonstrated that FcWRKY70 functions in drought tolerance by, at least partly, promoting production of putrescine via regulating ADC expression.