Well-conserved mitogen-activated protein kinase (MAPK) cascades are essential for orchestrating of a wide range of cellular processes in plants, including defense responses against pathogen attack. NAC transcription factors (TFs) play important roles in plant immunity, but their targets and how they are regulated remain largely unknown. Here, we identified the TF OsNAC29 as a key component of a MAPK signaling pathway involved in rice (Oryza sativa) disease resistance. OsNAC29 binds directly to CACGTG motifs in the promoters of OsTPS28 and OsCYP71Z2, which are crucial for the biosynthesis of the phytoalexin 5,10-diketo-casbene and consequently rice blast resistance. OsNAC29 positively regulates rice blast resistance by promoting the expression of of OsTPS28 and OsCYP71Z2, and the function of OsNAC29 is genetically dependent on OsCYP71Z2 and OsTPS28. Furthermore, OsNAC29 interacts with OsRACK1A and OsMAPK3/6 to form an immune complex; OsMAPK3 phosphorylates OsNAC29 at Thr304 to prevent its proteasome-mediated degradation and promote its function against rice blast fungus. Phosphorylation of OsNAC29 at Thr304 is induced upon Magnaporthe oryzae infection and chitin treatment. Our data demonstrate the positive role of the OsMAPK3–OsNAC29–OsTPS28/OsCYP71Z2 module in rice blast resistance, providing insights into the molecular regulatory network and fine-tuning of NAC TFs in rice immunity.

Plants need to fine‐tune defense responses to maintain a robust but flexible host barrier to various pathogens. Helix‐loop‐helix/basic helix‐loop‐helix (HLH/bHLH) complexes play important roles in fine‐tuning plant development. However, the function of these genes in plant immunity and how they are regulated remain obscure. Here, we identified an atypical bHLH transcription factor, Oryza sativa (Os)HLH46, that interacts with rice receptor‐like cytoplasmic kinase (RLCK) Os BRASSINOSTEROID‐SIGNALING KINASE1‐2 (OsBSK1‐2), which plays a key role in rice blast resistance. OsBSK1‐2 stabilized OsHLH46 both in vivo and in vitro. In addition, OsHLH46 positively regulates rice blast resistance, which depends on OsBSK1‐2. OsHLH46 has no transcriptional activation activity and interacts with a typical bHLH protein, OsbHLH6, which negatively regulates rice blast resistance. OsbHLH6 binds to the promoter of OsWRKY45 and inhibits its expression, while OsHLH46 suppresses the function of OsbHLH6 by blocking its DNA binding and transcriptional inhibition of OsWRKY45. Consistent with these findings, OsWRKY45 was up‐regulated in OsHLH46‐overexpressing plants. In addition, the oshlh46 mutant overexpressing OsbHLH6 is more susceptible to Magnaporthe oryzae than is the wild type, suggesting that OsHLH46 suppresses OsbHLH6‐mediated rice blast resistance. Our results not only demonstrated that OsBSK1‐2 regulates rice blast resistance via the OsHLH46/OsbHLH6 complex, but also uncovered a new mechanism for plants to fine‐tune plant immunity by regulating the HLH/bHLH complex via RLCKs.

Grain size is a key agronomic trait determining grain yields in crops. However, the molecular mechanisms of grain size regulation are still not fully understood. Here, we identified a cyclin-dependent kinase OsCDKF3 that controls grain development in rice (Oryza sativa). Knocking out OsCDKF3 decreased grain size and thousand grain weight. Moreover, we found that OsMPK6 interacts with and phosphorylates OsCDKF3 at Tyr22. Phosphorylation of Tyr22 contributes to the stability and function of OsCDKF3 in grain size regulation. Consistent with this, the phosphomimic OsCDKF3Y22D but not the dephosphomimic OsCDKF3Y22A complemented the grain defects of the oscdkf3 mutant, and knocking down of OsMPK6 also reduced grain size. In addition, OsSCL7, a grain size negative regulator, inhibited the autophosphorylation activity and promoted the degradation of OsCDKF3, as well as suppressed the interaction between OsCDKF3 and OsMPK6. Conversely, OsMPK6 interacted with OsSCL7 to suppress its transcriptional activity. Taken together, our findings revealed the crucial role of the OsMPK6–OsSCL7–OsCDKF3 module in fine regulation of grain size, providing insights into the important function of cyclin-dependent kinases in grain development.

Plant growth-promoting rhizobacteria (PGPR) are beneficial bacteria that play a crucial role in sustainable agriculture by enhancing plant growth through various mechanisms. This review examines the contributions of PGPR in improving nutrient availability, producing phytohormones, providing biocontrol against pathogens, and enhancing abiotic stress tolerance. By reducing the necessity for chemical fertilizers and pesticides, PGPR mitigate environmental impacts, enhance soil health, and support long-term agricultural productivity. However, challenges such as inconsistent performance across various soils, regulatory barriers, and limited farmer awareness hinder their widespread adoption. Recent advancements in nano-encapsulation technology, genetic engineering, and bioinformatics present promising solutions for overcoming these obstacles and enhancing PGPR efficacy. The incorporation of PGPR into biofertilizers, biopesticides, and integrated pest management (IPM) strategies offers a sustainable resolution to global agricultural challenges. This review addresses the current state of PGPR research, applications, and future directions for optimizing their use in promoting sustainable agriculture.