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Manipulating grain size demonstrates great potential for yield promotion in cereals since it is tightly associated with grain weight. Several pathways modulating grain size have been elaborated in rice, but possible crosstalk between the ingredients is rarely studied. OsmiR396 negatively regulates grain size through targeting OsGRF4 (GS2) and OsGRF8, and proves to be multi-functioning. Here we showed that expression of GS3 gene, a Gγ-protein encoding gene, that negatively regulates grain size, was greatly down-regulated in the young embryos of MIM396, GRF8OE and GS2OE plants, indicating possible regulation of GS3 gene by OsmiR396/GRF module. Meanwhile, multiple biochemical assays proved possible transcriptional regulation of OsGRF4 and OsGRF8 proteins on GS3 gene. Further genetic relation analysis revealed tight genetic association between not only OsmiR396 and GS3 gene, but also GS2 and GS3 gene. Moreover, we revealed possible regulation of GS2 on four other grain size-regulating G protein encoding genes. Thus, the OsmiR396 pathway and the G protein pathway cross talks to regulate grain size. Therefore, we established a bridge linking the miRNA-transcription factors pathway and the G-protein signaling pathway that regulates grain size in rice., (© 2024. The Author(s).)

Leaf morphology is a crucial agronomic characteristic of rice that influences crop yield directly. One primary cause of rice leaf rolling can be attributed to alterations in bulliform cells. Several HD-ZIP IV genes have been identified to be epidemical characterized and function in leaf rolling in rice. Still others need to be studied to fully understand the overall function of HD-ZIP IV family. Among the nine ROC genes encoding HD-ZIP IV family transcription factors in rice, ROC1 exhibits the highest expression in the leaves. Overexpression of ROC1 decreased the size of bulliform cells, and thus resulted in adaxially rolled leaves. To the contrary, knockout of ROC1 (ROC1KO) through Crispr-cas9 system enlarged bulliform cells, and thus led to abaxially rolled leaves. Moreover, ROC1KO plants were sensitive to drought. ROC1 could form homodimers on its own, and heterodimers with ROC5 and ROC8 respectively. Compared to ROC1KO plants, leaves of the ROC1 and ROC8 double knocked out plants (ROC1/8DKO) were more severely rolled abaxially due to enlarged bulliform cells, and ROC1/8DKO plants were more drought sensitive. However, overexpression of ROC8 could not restore the abaxial leaf phenotype of ROC1KO plants. Therefore, we proved that ROC1, a member of the HD-ZIP IV family, regulated leaf rolling and drought stress response through tight association with ROC5 and ROC8., (© 2024. The Author(s).)

Brown planthopper (BPH) is the most destructive insect pest to rice that causes tremendous yield loss each year in rice planting Asia and South-East Asia areas. Compared with traditional chemical-based treatment, utilization of plant endogenous resistance is a more effective and environmental-friendly way for BPH control. Accordingly, quite a few quantitative trait loci (QTLs) for BPH resistance were cloned using forward genetics. However, BPH is apt to change quickly into new biotypes to overcome plant resistance, therefore, new resistance resources and genes are continuously needed. miRNAs are important regulators in both plant development and physiological regulation including immunity, and might be used as effective supplements for BPH resistance QTLs. miR159 is an ancient and conserved miRNA. In this study, we found that each OsMIR159 gene in rice responded to BPH feeding very obviously, and genetic function assay proved them to negatively regulate BPH resistance, with STTM159 showing resistance to BPH, and over expression of OsmiR159d susceptible to BPH. One target genes of OsmiR159, OsGAMYBL2, positively regulated BPH resistance. Further biochemical studies revealed that OsGAMYBL2 could directly bind to the promoter of G-protein γ subunit encoding GS3 gene and repress its expression. And genetically, GS3 responded to BPH feeding promptly and negatively regulated BPH resistance, GS3 over expression plants were susceptible to BPH, while GS3 knock-out plants were resistant to BPH. Thus, we identified new function of OsmiR159-OsGAMYBL2 in mediating BPH response, and revealed a new OsmiR159-G protein pathway that mediates BPH resistance in rice., (© 2023. The Author(s).)

Background: Rice (Oryza sativa) panicle architecture is the major determinant of the ideal plant architecture that directly influence yield potential. Many genes influencing development of primary branches, secondary branches, spikelet and pedicel would also influence panicle architecture, which is thus a complex trait regulated by genes from various aspects. miR156, an extensively studied miRNA, has recently emerged as promising target for crop improvement because of its role in plant architecture regulation, such as the number of tillers, plant height and the panicle architecture. Increasing evidence suggests that miR156 might play an important role in panicle architecture regulation., Main Body: To study the detailed function of miR156 in rice panicle architecture regulation, we examined the genetic interaction or transcriptional regulation of miR156/OsSPL to other panicle regulating genes. Our results revealed that expression of many panicle related genes were influenced by miR156. Through biochemical analysis, we further proved that miR156 directly regulated the axillary meristem regulating gene, LAX1, at the transcription level. And the intimate relations between miR156 and LAX1, and miR156 and LAX2 were also uncovered by genetic analysis. On the other hand, a tight genetic linkage between miR156 and RCN2, the panicle branch promoting gene, was also detected, which suggested a buffering mechanism for the miR156 mediated panicle architecture regulation. Furthermore, genetic analysis also demonstrated that miR156 functioned in the same pathway with OsRA2 to regulate pedicel length., Short Conclusion: Altogether, miR156 integrates several genetic pathways mediated by genes such as LAX1, LAX2, RCN2 and OsRA2, and comprehensively regulates panicle development in rice. Based on these analysis, we concluded that miR156 acts as an important regulator for panicle architecture through influencing various aspects of panicle development.

Background: In plants, basic helix-loop-helix (bHLH) proteins form the largest transcription factor (TF) family. Among them, HLH proteins are a small group of atypical members that lack the basic domain, and form dimers with bHLH proteins. Although bHLH proteins have been proved to play important roles in plant development and physiology, the function of HLH proteins is rarely studied, not to mention in plant biotic resistance. Brown planthopper (BPH) is a kind of rice-specific insect that causes devastating yield losses each year., Results: In this study, we identified OsHLH61 gene that encodes HLH protein. OsHLH61 gene could be highly induced by BPH infestation. Furthermore, Methyl Jasmonic acid (Me-JA) and cis-12-oxo- phytodienoic acid (OPDA) induced expression of OsHLH61, while SA repressed it. We knocked down expression of OsHLH61 by RNA interference (RNAi), the transgenic plants were susceptible to BPH infestation. RNA-seq analysis revealed that some pathogen-related (PR) genes in the Salicylic acid (SA) signaling pathway that mediate plant immunity were obviously down-regulated in the OsHLH61 RNAi plants. Meanwhile, yeast two-hybrid assay and bimolecular luciferase complementation (BiLC) analysis identified bHLH096 to be an interacting factor of OsHLH61. Also, some PR genes were down-regulated in the OsbHLH96 over expressing lines. Expression of OsbHLH96 was inhibited. Besides, OsbHLH96 might interact with Jasmonate Zim-Domain3 (OsJAZ3)., Conclusion: Altogether, we identified an OsHLH61-OsbHLH96 complex that might mediate defense to BPH through regulating PR genes. And OsHLH61-OsbHLH96 might be important in mediating SA and JA signaling crosstalk.