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SUMMARY: Cytochrome P450 proteins (CYPs) play critical roles in plant development and adaptation to fluctuating environments. Previous reports have shown that CYP86A proteins are involved in the biosynthesis of suberin and cutin in Arabidopsis. However, the functions of these proteins in rice remain obscure. In this study, a rice mutant with incomplete male sterility was identified. Cytological analyses revealed that this mutant was defective in anther development. Cloning of the mutant gene indicated that the responsible mutation was on OsCYP86A9. OsMYB80 is a core transcription factor in the regulation of rice anther development. The expression of OsCYP86A9 was abolished in the anther of osmyb80 mutant. In vivo and in vitro experiments showed that OsMYB80 binds to the MYB‐binding motifs in OsCYP86A9 promoter region and regulates its expression. Furthermore, the oscyp86a9 mutant exhibited an impaired suberin deposition in the root, and was more susceptible to drought stress. Interestingly, genetic and biochemical analyses revealed that OsCYP86A9 expression was regulated in the root by certain MYB transcription factors other than OsMYB80. Moreover, mutations in the MYB genes that regulate OsCYP86A9 expression in the root did not impair the male fertility of the plant. Taken together, these findings revealed the critical roles of OsCYP86A9 in plant development and proposed that OsCYP86A9 functions in anther development and root suberin formation via two distinct tissue‐specific regulatory pathways. Significance Statement: The cytochrome P450 subfamily CYP86A is very important for plant development. However, their functions remain obscure in rice. Here, we reported that OsCYP86A9, a member of CYP86A subfamily, is critical for the development of anther and root suberin, and these functions are determined by two distinct tissue‐specific regulatory pathways. [ABSTRACT FROM AUTHOR]

Alternative splicing can generate multiple mRNAs that differ in their untranslated regions or coding sequences, and these differences might affect mRNA stability or result in different protein isoforms with diverse functions and/or localizations. In this study, we isolated a sterile mutant in rice with abnormal meiosis of microspore mother cells and megaspore mother cells that carried a point mutation in OsRAD1 gene. Cloning of OsRAD1 cDNAs revealed three transcript variants, named as OsRAD1.1, OsRAD1.2 and OsRAD1.3, respectively, which were derived from alternative splicing of the last intron. Proteins derived from the three transcripts were mostly identical except the difference in the very C-terminal domain. The three transcripts exhibited similar expression patterns in various tissues, but the expression level of OsRAD1.1 was the highest. Specific knockout of OsRAD1.1 led to sterility, while knockout of OsRAD1.2 and OsRAD1.3 together did not change the plant fertility. Overexpression of OsRAD1.2 and OsRAD1.3 cDNAs in OsRAD1.1-specific mutant did not complement the plant fertility. Yeast two-hybrid assay showed that OsRAD1.1, but not OsRAD1.2 and OsRAD1.3, interacted with the three other meiosis proteins OsHUS1, OsRAD9 and OsRAD17, suggesting that the C-terminal domain of OsRAD1.1 is critical for the protein function.

Meiotic recombination plays a central role in maintaining genome stability and increasing genetic diversity. Although meiotic progression and core components are widely conserved across kingdoms, significant differences remain among species. Here we identify a rice gene ABERRANT GAMETOGENESIS 1 (AGG1) that controls both male and female gametogenesis. Cytological and immunostaining analysis showed that in the osagg1 mutant the early recombination processes and synapsis occurred normally, but the chiasma number was dramatically reduced. Moreover, OsAGG1 was found to interact with ZMM proteins OsHEI10, OsZIP4, and OsMSH5. These results suggested that OsAGG1 plays an important role in crossover formation. Phylogenetic analysis showed that OsAGG1 is a plant-specific protein with a highly conserved N-terminal region. Further genetic and protein interaction analyses revealed that the conserved N-terminus was essential for the function of the OsAGG1 protein. Overall, our work demonstrates that OsAGG1 is a novel and critical component in rice meiotic crossover formation, expanding our understanding of meiotic progression. This study identified a plant-specific gene ABERRANT GAMETOGENESIS 1 that is required for meiotic crossover formation in rice. The conserved N-terminus of the AGG1 protein was found to be essential for its function. [ABSTRACT FROM AUTHOR]