Plant Physiology最新文献

A plant architecture with upright leaves promotes canopy photosynthesis, thus enhancing biomass production. Brassinosteroid (BR) biosynthesis has been positively linked with rice leaf angle; however, the underlying molecular mechanisms remain obscure. Here, we report that OsPIL13, a bHLH transcription factor, modulates rice (Oryza sativa L.) leaf angle by orchestrating BR biosynthesis. Phenotypic and cytological analysis demonstrated that OsPIL13 modulates longitudinal cell elongation in the adaxial lamina joint, with ospil13 mutants showing a 48% reduction in leaf angles and OsPIL13 overexpression lines exhibiting an 86% increase in leaf angles relative to cv. Dongjin (WT), ultimately shaping rice leaf angle. Interestingly, the WT and OsPIL13 transgenic plants had contrasting responses to brassinazole (a specific BR biosynthesis inhibitor), implying that the BR pathway is involved in OsPIL13-mediated leaf angle. Further studies identified that OsPIL13 binds to the exon of OsDWF4, encoding the rate-limiting enzyme in BR synthesis CYP90B1. The content of endogenous brassinolide decreased in the lamina joints of the ospil13 mutant relative to WT, whereas the OsPIL13 overexpression line resulted in an increase. Moreover, mutation of OsDWF4 in the background of the WT and OsPIL13 overexpression line was associated with a reduced leaf angle compared to their respective WTs. Our data reveal that OsPIL13 modulates rice leaf angle by regulating BR homeostasis through the OsDWF4-mediated pathway.

Black rot (BR), caused by Xanthomonas campestris pv. campestris (Xcc), severely hampers Brassica production worldwide. Type III effectors (T3Es), which include transcription activator-like effectors (TALEs) and Xanthomonas outer proteins (Xops), are virulence factors for Xcc in host crops, such as rice, pepper, and cassava. However, their effects in Brassica remain unclear. Here, we analyzed 70 Xcc strains collected from locations worldwide and evaluated their pathogenicity in 5 Brassica accessions, identifying 6 highly aggressive strains. Southern blotting revealed TALEs in only ∼5% of Chinese Xcc strains, and Δtal mutants retained full virulence, indicating that these TALEs are dispensable for BR occurrence in Brassica crops. Whole-genome sequencing of 5 strains identified 33 Xops. Moreover, targeted mutagenesis of xopK, xopQ, xopX-1, xopAM, and xopN indicated host-dependent functions in cabbage. Deletion of xopQ, xopX-1, xopAM, or xopN increased disease indices by more than 10% in cabbage line G1180 (ΔxopN >20%), while bacterial counts also increased. In cabbage line G87-534, deletion of ΔxopK or ΔxopN reduced both disease indices and bacterial counts. Transient expression of XopQ, XopX-1, and XopN triggered a hypersensitive response in cabbage, and reverse transcription quantitative PCR (RT-qPCR) analyses revealed that 5 effectors suppressed the expression of pathogenesis-related protein 1 (PR1) or WRKY transcription factor (WRKY) genes associated with pattern-triggered immunity. Our study revealed that Xops, rather than TALEs, dominate virulence in Xcc‒Brassica interactions, in striking contrast to the pattern in other Xanthomonas pathosystems. This comprehensive T3E profile of Chinese Xcc provides a framework for developing Brassica crops with targeted resistance to BR.

Phosphorus (P) is a macronutrient necessary for plant growth and development. Phosphorus deficiency usually causes changes in plant secondary metabolites, mainly including anthocyanin synthesis. However, the regulatory mechanism of anthocyanin synthesis in Malus spectabilis leaves under low-phosphorus conditions remains unclear. In this study, anthocyanin accumulation in M. spectabilis leaves gradually increased as phosphorus application decreased, reaching a maximum anthocyanin concentration at 300 µM phosphorus. Through transcriptome sequencing, MsSPX4 was identified as a key regulatory factor for anthocyanin synthesis under low-phosphorus conditions. The protein complex MsSPX4-MsPHL11 was confirmed through Y2H, BiFC, and LCI assays, and its function was validated through transient and stable transformation experiments in Malus spp. Under conditions of sufficient Pi, MsSPX4 inhibited MsPHL11 activity by interacting with MsPHL11, whereas phosphorus starvation disrupted the MsSPX4/MsPHL11 complex, alleviating the inhibitory effect on MsPHL11. MsPHL11 bound to the P1BS element on the MsWRKY91 promoter to activate MsWRKY91 expression. Furthermore, MsWRKY91 activated MsF3'H expression by binding to the W-box element on the MsF3'H promoter, thereby positively regulating anthocyanin biosynthesis. Overexpression of MsPHL11 promoted the expression of genes related to phosphorus metabolism and transport, thereby increasing M. 'Gala' low-phosphorus resistance. By contrast, MsSPX4-stabilized transgenic M. 'Gala' lines exhibited lower phosphorus resistance. Our results elucidate the mechanism by which the MsSPX4/MsPHL11-MsWRKY91 module regulates anthocyanin synthesis in M. spectabilis leaves under low-phosphorus conditions. These findings provide a reference for further exploration of the molecular mechanism of anthocyanin synthesis in plants under low-phosphorus conditions.