Molecular Plant最新文献

Alternative splicing plays a vital role in plant immunity, but how plants stringently and selectively regulate alternative splicing to coordinate immunity and growth is poorly understood. Here, we report that H₂O₂-triggered phosphorylation of the RNA-binding protein RRM2R releases a retained-intron brake in OsMAPKKK18 encoding a mitogen-activated protein kinase kinase kinase to orchestrate plant immunity and growth in rice. We found that, without pathogen infection, OsMAPKKK18β transcripts containing a retained intron are subjected to nonsense-mediated mRNA decay to promote plant growth. Upon Magnaporthe oryzae pathogen invasion, H₂O₂ activates the protein kinase OsCLK1 to phosphorylate and stabilize RRM2R, which interacts with OsRNPS1A/B to recruit spliceosome machinery and promote the production of OsMAPKKK18α transcripts without the retained intron to promote rice immunity. Furthermore, we revealed that after the endogenous H₂O₂ is consumed or degraded by peroxidases or catalases, decreased abundance of RRM2R reduces the accumulation of OsMAPKKK18α transcripts to avoid autoimmunity in rice. Taken together, the results of our study uncover H₂O₂-controlled OsMAPKKK18 intron retention as a novel molecular switch for orchestrating immunity and growth in rice.

Transcriptional regulation of cold-responsive genes plays crucial roles in plant cold tolerance, but the transcription factors (TFs)-centered regulatory networks remain largely unclear. In this study, we show that Monoculm1 (MOC1), a critical TF controlling tiller number and plant height in rice, positively regulates rice cold tolerance at the seedling stage. We found that OsMPK4, a mitogen-activated protein kinase, phosphorylates and stabilizes MOC1 under cold stress. Further investigations revealed that MOC1 recruits the TFs OsbZIP79 and OsNAC5 to form a triple complex and subsequently enhances their stability by inhibiting proteasome-mediated degradation under cold stress. Notably, we found that the OsbZIP79-MOC1-OsNAC5 complex activates several cold-responsive genes, including Dehydration-responsive element-binding factor 1G (OsDREB1G), to confer rice cold tolerance. Haplotype analysis of the OsDREB1G promoter in > 10,000 rice accessions identified the favorable haplotype and key variants that endow rice cold tolerance. Collectively, our work demonstrates a pivotal role of the OsMPK4-OsbZIP79-MOC1-OsNAC5-OsDREB1G module in regulating rice cold tolerance and provides genetic targets for improving cold tolerance through molecular breeding.

Both activation and termination of DNA damage response (DDR) are essential to maintain genome stability. It is well-known that the histone variant H2AX is rapidly phosphorylated to activate DDR in eukaryotes. But how H2AX signaling is terminated remains poorly understood, especially in plants. Through forward genetic screening in Arabidopsis, we find that the DNA Damage Response Mutant 5 (ddrm5) mutant is hypersensitive to DNA damage-inducing reagents. Gene mapping and genetic complementation analysis reveal that DDRM5 encodes a plant-unique phosphatase MAIL3, whose phosphatase domain is necessary and sufficient for its function in DDR. Biochemically, MAIL3 physically interacts with and dephosphorylates H2AX, promoting its polyubiquitination at Lys103 and Lys127 by the E3 ubiquitin ligase SCF^AFB1, which results in H2AX degradation through the proteasome. Genetically, loss of H2AX or overexpression of AFB1 rescue the DDR defects of the mail3 mutant. Taken together, this study identifies MAIL3 and SCF^AFB1 as the first phosphatase and the first E3 ubiquitin ligase for plant H2AX, highlighting the importance of H2AX dephosphorylation and polyubiquitination in DDR termination.