A single recessive gene, Multi-Grain Spikelet 1 (MGS1), governs the multiple-grain spikelet trait in sorghum. The natural variants mgs19E and mgs1BA45 trigger adjacent double-pistil primordia, significantly boosting grain numbers per panicle, suggesting potential strategies for breeding high-yield sorghum.

Parasitism with Striga poses a major threat to global food production. Striga germination and growth rely on strigolactones (SLs) exuded by crop roots under phosphate (Pi)-deficient conditions, although the mechanism of this host-parasite interaction remains elusive. In this study, transcriptomic and functional analyses of sorghum treated with Pi deficiency or the SL GR245DS identify two ABC transporter G (ABCG) transporters of SL, Sorghum biocolor strigolactones transporter 1 (SbSLT1) and SbSLT2. Using AlphaFold2 and amino acid conversion mutants, we identify highly conserved amino acids in SL transport channels essential for transport function. Sorghum lines with single or double knockouts of these transporters exhibit significantly reduced SL secretion from roots, leading to decreased Striga germination and parasitism in field experiments and consequently reducing the grain loss under Striga infestation. This study thus describes the mechanism of SL exudation in monocots and defines conserved residues essential for SL transporter function, offering a potential strategy for enhancing crop resistance to Striga parasitism.

Endoplasmic reticulum-associated degradation (ERAD) is an important mechanism for degrading misfolded proteins, and is mediated by different complexes containing several conserved ER-localized ubiquitin ligases, such as Hrd1, Doa10, and gp78. Recent studies have shown that the ERAD machinery is conserved in eukaryotes. However, it remains unknown whether plants have gp78 homologs. We report a functional study of Arabidopsis homologs of gp78 and their involvement in ERAD. T-DNA insertion mutations in Arabidopsis gp78 genes, AtGP78A and AtGP78B, increased degradation of mutated brassinosteroid (BR) receptors, bri1-5 and bri1-9, leading to lower activation of the signaling protein BES1, and thereby enhancing the dwarf phenotypes of bri1-5/9. This is different from the effects of knockout in known ERAD components, which suppress the dwarf phenotypes of bri1-5/9. AtGP78s interacted with and affected the stability of AtOS9, but not other components in the AtHRD1 complex. AtOS9 accumulated in atgp78a-1 atgp78b bri1-5/9, and knockout of AtOS9 rescued the enhanced-dwarf phenotypes of atgp78a-1 atgp78b bri1-5/9. We determined that AtGP78s were involved in plant ERAD by modulating the stability of AtOS9. Taken together, our results not only reveal AtGP78s as new ERAD components but also reveal a relationship between AtGP78s and the AtHRD1 complex in plants.

The phenomenon of multiple-grain spikelets is frequently observed in gramineous crops. In the case of dual-floret spikelets, the upper fertile floret develops normally to form a single grain, while the lower sterile floret undergoes abortion. Here we elucidate the role of Double-Grain 1 (DG1), a gene encoding a homeobox-domain-containing protein, in regulating the lower floret meristem activity and double-grain spikelet trait in sorghum. A 35.7-kb paracentric inversion in the DG1 promoter region leads to increased DG1 expression, probably by reducing repressive histone modifications. This increase in DG1 expression transforms the degenerated lower floret into a fertile one. The use of the superior DG1 allele results in an increase of approximately 40.7% to 46.1% in grain number per panicle and a 10.1% to 14.3% increase in overall grain yield. Our findings shed light on the sorghum double-grain spikelet characteristic, offering valuable insights for high-yield breeding designs in cereals.

Dear Editor, Lignocellulose,primarily composed of cellulose,hemicellulose,and lignin,is the most abundant renewable bioresource used across industrial and agricultural sectors in modern society(Deng et al.,2023).However,the recalcitrance of lignocellulosic biomass hinders its utilization efficiency.As the predominant hemicellulose polysaccharide that cross-links with cellulose and lignin in grasses,xylan is an ideal target for manipulation to alter cell wall properties(Bhatia et al.,2017;Zhang et al.,2023).

Weeds bring a serious challenge to crop production, and herbicides is the most effective and economic way to manage it in field. Sorghum is a critical crop for staple food, fodder, and biofuel. However, the lack of herbicide-resistant sorghum germplasm severely impedes its production. Here, we conducted a large-scale screening and identified 13 sorghum mutant lines resistant to imidazolinone (IMI) herbicides. Two unique mutation sites in SbALS (acetolactate synthase), thus namely Sbals-1 (A93T) and Sbals-2 (S624N) are discovered, both enhance sorghum tolerance to imazamox. Notably, under high concentrations of imazamox, sbals-1 presented a superior growth phenotype and elevated SbALS activity than sbals-2, a difference that can be attributed to the predicted protein structures. Breeding with Sbals, both grain- and grass-type sorghum, shows great weed control and field performance. The herbicide imazamox resistance is further evaluated in a soybean population for sorghum-soybean strip intercropping, identifying 123 highly resistant soybean varieties. Field intercropping tests indicated health growth of both soybean and sorghum lines post-imazamox treatment, which enhance field clearance of weed. This study, therefore, provides valuable insights not only for herbicide-resistant sorghum breeding but also for the successful implementation of efficient and sustainable cereal-legume intercropping systems.

Sorghum, the fifth most important food crop globally, is a source of silage forage, fiber, syrup, and biofuel. Moreover, it is widely recognized as an ideal model crop for studying stress biology becaused of its ability to tolerate multiple abiotic stresses, including high salt-alkali conditions, drought, and heat. However, functional genomics studies on sorghum have been challenging, primarily due to the limited availability of genetic resources and effective genetic transformation techniques. In this study, we developed the Sorghum Genomics and Mutation Database (SGMD), aiming to advance the genetic understanding of sorghum. Our effort encompassed a telomere-to-telomere genome assembly of an inbred sorghum line, E048, yielding 729.46 Mb of sequence data representing the complete genome. Alongside the high-quality sequence data, a gene expression atlas covering 13 distinct tissues was developed. We constructed a saturated ethyl methane sulfonate mutant library comprising 13,226 independent mutants. Causal genes in chlorosis and leafy mutants from the library were easily identified by leveraging the MutMap and MutMap+ methodologies, demonstrating the powerful application of this library for identifying functional genes. To facilitate sorghum research, we performed whole-genome sequencing of 179 M2 mutant lines, resulting in 2,291,074 mutations that covered 97.54% of all genes. In addition, an Agrobacterium-mediated sorghum transformation platform was established for gene function studies. In summary, this work establishes a comprehensive platform and provides valuable resources for functional genomics investigations and genetic improvement of sorghum.

The endoplasmic reticulum-associated degradation (ERAD) system eliminates misfolded and short-lived proteins to maintain physiological homeostasis in the cell. We have previously reported that ERAD is involved in salt tolerance in Arabidopsis. Given the central role of the phytohormone abscisic acid (ABA) in plant stress responses, we sought to identify potential intersections between the ABA and the ERAD pathways in plant stress response. By screening for the ABA response of a wide array of ERAD mutants, we isolated a gain-of-function mutant, doa10a-1, which conferred ABA hypersensitivity to seedlings. Genetic and biochemical assays showed that DOA10A is a functional E3 ubiquitin ligase which, by acting in concert with specific E2 enzymes, mediates mono-ubiquitination of the ABA receptor, followed by their relocalization to the plasma membrane. This in turn leads to enhanced ABA perception. In summary, we report here the identification of a novel RING-type E3 ligase, DOA10A, which regulates ABA perception by affecting the localization and the activity of ABA receptors through their mono-ubiquitination.

The use of alkaline salt lands for crop production is hindered by a scarcity of knowledge and breeding efforts for plant alkaline tolerance. Through genome association analysis of sorghum, a naturally high-alkaline-tolerant crop, we detected a major locus, Alkaline Tolerance 1 (AT1), specifically related to alkaline-salinity sensitivity. An at1 allele with a carboxyl-terminal truncation increased sensitivity, whereas knockout of AT1 increased tolerance to alkalinity in sorghum, millet, rice, and maize. AT1 encodes an atypical G protein γ subunit that affects the phosphorylation of aquaporins to modulate the distribution of hydrogen peroxide (H2O2). These processes appear to protect plants against oxidative stress by alkali. Designing knockouts of AT1 homologs or selecting its natural nonfunctional alleles could improve crop productivity in sodic lands.

Ubiquitination-mediated protein degradation in both the 26S proteasome and vacuole is an important process in abscisic acid (ABA) signaling. However, the role of deubiquitination in this process remains elusive. Here, we demonstrate that two deubiquitinating enzymes (DUBs), ubiquitin-specific protease 12 (UBP12) and UBP13, modulate ABA signaling and drought tolerance by deubiquitinating and stabilizing the endosomal sorting complex required for transport-I (ESCRT-I) component vacuolar protein sorting 23A (VPS23A) and thereby affect the stability of ABA receptors in Arabidopsis thaliana. Genetic analysis showed that VPS23A overexpression could rescue the ABA hypersensitive and drought tolerance phenotypes of ubp12-2w or ubp13-1. In addition to the direct regulation of VPS23A, we found that UBP12 and UBP13 also stabilized the E3 ligase XB3 ortholog 5 in A. thaliana (XBAT35.2) in response to ABA treatment. Hence, we demonstrated that UBP12 and UBP13 are previously unidentified rheostatic regulators of ABA signaling and revealed a mechanism by which deubiquitination precisely monitors the XBAT35/VPS23A ubiquitination module in the ABA response.

Accumulating evidence has revealed that the ubiquitin proteasome system plays fundamental roles in the regulation of diverse cellular activities in eukaryotes. The ubiquitin protein ligases (E3s) are central to the proteasome system because of their ability to determine its substrate specificity. Several studies have demonstrated the essential role of a group of ER (endoplasmic reticulum)-localized E3s in the positive or negative regulation of cell homeostasis. Most ER-related E3s are conserved between plants and mammals, and a few plant-specific components have been reported. In this review, we summarize the functions of ER-related E3s in plant growth, ER-associated protein degradation and ER-phagy, abiotic and biotic stress responses, and hormone signaling. Furthermore, we highlight several questions that remain to be addressed and suggest directions for further research on ER-related E3 ubiquitin ligases.

Due to climate change, drought has become a severe abiotic stress that affects the global production of all crops. Elucidation of the complex physiological mechanisms underlying drought tolerance in crops will support the cultivation of new drought-tolerant crop varieties. Here, two drought-tolerant lines, RIL70 and RIL73, and two drought-sensitive lines, RIL44 and RIL93, from recombinant inbred lines (RIL) generated from maize drought-tolerant line PH4CV and drought-sensitive line F9721, were selected for a comparative RNA-seq study. Through transcriptome analyses, we found that gene expression differences existed between drought-tolerant and -sensitive lines, but also differences between the drought-tolerant lines, RIL70 and RIL73. ZmbHLH124 in RIL73, named as ZmbHLH124T-ORG which origins from PH4CV and encodes a bHLH type transcription factor, was specifically up-regulated during drought stress. In addition, we identified a substitution in ZmbHLH124 that produced an early stop codon in sensitive lines (ZmbHLH124S-ORG ). Overexpression of ZmbHLH124T-ORG , but not ZmbHLH124S-ORG , in maize and rice enhanced plant drought tolerance and up-regulated the expression of drought-responsive genes. Moreover, we found that ZmbHLH124T-ORG could directly bind the cis-acting elements in ZmDREB2A promoter to enhance its expression. Taken together, this work identified a valuable genetic locus and provided a new strategy for breeding drought-tolerant crops.

Endoplasmic reticulum-associated degradation (ERAD) is known to regulate plant responses to diverse stresses, yet its underlying molecular mechanisms and links to various stress signaling pathways are poorly understood. Here, we show that the ERAD component ubiquitin-conjugating enzyme UBC32 positively regulates drought tolerance in Arabidopsis thaliana by targeting the aquaporins PIP2;1 and PIP2;2 for degradation. Furthermore, we demonstrate that the RING-type ligase Rma1 acts together with UBC32 and that the E2 activity of UBC32 is essential for the ubiquitination of Rma1. This complex ubiquitinates a phosphorylated form of PIP2;1 at Lys276 to promote its degradation, thereby enhancing plant drought tolerance. Extending these molecular insights into crops, we show that overexpression of Arabidopsis UBC32 also improves drought tolerance in rice (Oryza sativa). Thus, beyond uncovering the molecular basis of an ERAD-regulated stress response, our study suggests multiple potential strategies for engineering crops with improved drought tolerance.

The Salt-Overly-Sensitive (SOS) signaling module, comprising the sodium-transport protein SOS1 and the regulatory proteins SOS2 and SOS3, is well known as the central salt excretion system, which helps protect plants against salt stress. Here we report that VPS23A, a component of the ESCRT (endosomal sorting complex required for transport), plays an essential role in the function of the SOS module in conferring plant salt tolerance. VPS23A enhances the interaction of SOS2 and SOS3. In the presence of salt stress, VPS23A positively regulates the redistribution of SOS2 to the plasma membrane, which then activates the antiporter activity of SOS1 to reduce Na+ accumulation in plant cells. Genetic evidence demonstrated that plant salt tolerance achieved by the overexpression of SOS2 and SOS3 dependeds on VPS23A. Taken together, our results revealed that VPS23A is a crucial regulator of the SOS module and affects the localization of SOS2 to the cell membrane. Moreover, the strong salt tolerance of Arabidopsis seedlings conferred by the engineered membrane-bound SOS2 revealed the significance of SOS2 sorting to the cell membrane in achieving its function, providing a potential strategy for crop salt tolerance engineering.

Abscisic acid (ABA) is the key phytohormone in plant drought tolerance and stress adaptation. The clade A protein phosphatase 2Cs (PP2Cs) like ABI1 (ABA-INSENSITIVE 1) work as coreceptors of ABA and regulate multiple ABA responses. Ubiquitination of ABI1 has been proven to play important regulatory roles in ABA signaling. However, the specific ubiquitin conjugating enzyme (E2) involved is unknown. Here, we report that UBC27 is an active E2 that positively regulates ABA signaling and drought tolerance. UBC27 forms the E2-E3 pair with the drought regulator RING E3 ligase AIRP3. Both UBC27 and AIRP3 interact with ABI1 and affect the ubiquitination and degradation of ABI1. ABA activates the expression of UBC27, inhibits the proteasome degradation of UBC27, and enhances the interaction between UBC27 and ABI1 to increase its activity. These findings uncover a regulatory mechanism in ABA signaling and drought response and provide a further understanding of the plant ubiquitination system and ABA signaling pathway.

A myriad of abiotic stress responses in plants are controlled by abscisic acid (ABA) signaling. ABA receptors can be degraded by both the 26S proteasome pathway and vacuolar degradation pathway after processing via the endosomal sorting complex required for transport (ESCRT) proteins. Despite being essential for ABA signaling, the upstream regulators of ESCRTs remain unknown. Here, we report that the ESCRT-I component VPS23A is an unstable protein that is degraded via the ubiquitin-proteasome system (UPS). The UEV domain of VPS23A physically interacts with the two PSAP motifs of XBAT35, an E3 ubiquitin ligase, and this interaction results in the deposition of K48 polyubiquitin chains on VPS23A, marking it for degradation by 26S proteasomes. We showed that XBAT35 in plants is a positive regulator of ABA responses that acts via the VPS23A/PYL4 complex, specifically by accelerating VPS23A turnover and thereby increasing accumulation of the ABA receptor PYL4. This work deciphers how an ESCRT component is regulated in plants and deepens our understanding of plant stress responses by illustrating a mechanism whereby crosstalk between the UPS and endosome-vacuole-mediated degradation pathways controls ABA signaling.

玉米是我国主要的粮食作物,在人民生活和国民经济中有着举足轻重的作用,确保其持续稳产对保障我国粮食安全及服务供给侧结构性改革,具有十分重要的战略意义.尽管传统杂交育种技术在玉米遗传改良工作中取得了一系列重要成绩,但是尚不能满足当前人民日益增长的美好生活需要.随着生物技术的迅猛发展,分子育种已成为玉米育种的重要方向和必然选择,其中分子模块设计育种将多学科相结合,实现全基因组水平上的多模块优化组装,对未来的玉米育种事业将起到极大的推动作用.文章综述了玉米育种技术的发展历程以及分子模块设计育种技术在玉米育种中取得的成绩,并对未来的研究提出了展望.

Zea mays is an important crop that is sensitive to drought stress, but survival rates and growth status remain strong in some drought-tolerant lines under stress conditions. Under drought conditions, many biological processes, such as photosynthesis, carbohydrate metabolism and energy metabolism, are suppressed, while little is known about how the transcripts of genes respond to drought stress in the genome-wide rang in the seedling stage. In our study, the transcriptome profiles of two maize recombination inbred lines (drought-tolerant RIL70 and drought-sensitive RIL93) were analyzed at different drought stages to elucidate the dynamic mechanisms underlying drought tolerance in maize seedlings during drought conditions. Different numbers of differentially expressed genes presented in the different stages of drought stress in the two RILs, for the numbers of RIL93 vs. RIL70 were: 9 vs. 358, 477 vs. 103, and 5207 vs. 152 respectively in DT1, DT2, and DT5. Gene Ontology enrichment analysis revealed that in the initial drought-stressed stage, the primary differentially expressed genes involved in cell wall biosynthesis and transmembrane transport biological processes were overrepresented in RIL70 compared to RIL93. On the contrary, differentially expressed genes profiles presented at 2 and 5 day-treatments, the primary differentially expressed genes involved in response to stress, protein folding, oxidation-reduction, photosynthesis and carbohydrate metabolism, were overrepresented in RIL93 compared to RIL70. In addition, the transcription of genes encoding key members of the cell cycle and cell division processes were blocked, but ABA- and programmed cell death-related processes responded positively in RIL93. In contrast, the expression of cell cycle genes, ABA- and programmed cell death-related genes was relatively stable in RIL70. The results we obtained supported the working hypothesis that signaling events associated with turgor homeostasis, as established by cell wall biosynthesis regulation- and aquaporin-related genes, responded early in RIL70, which led to more efficient detoxification signaling (response to stress, protein folding, oxidation-reduction) during drought stress. This energy saving response at the early stages of drought should facilitate more cell activity under stress conditions and result in drought tolerance in RIL70.