Functional analysis of auxin receptor OsTIR1/OsAFB family members in rice grain yield, tillering, plant height, root system, germination, and auxinic herbicide resistance. Issue 5 (10th December 2020) - Guo, Fu
Summary: Auxin regulates almost every aspect of plant growth and development and is perceived by the TIR1/AFB auxin co‐receptor proteins differentially acting in concert with specific Aux/IAA transcriptional repressors. Little is known about the diverse functions of TIR1/AFB family members in species other than Arabidopsis. We created targeted OsTIR1 and OsAFB2 – 5 mutations in rice using CRISPR/Cas9 genome editing, and functionally characterized the roles of these five members in plant growth and development and auxinic herbicide resistance. Our results demonstrated that functions of OsTIR1/AFB family members are partially redundant in grain yield, tillering, plant height, root system and germination. Ostir1, Osafb2 and Osafb4 mutants exhibited more severe phenotypes than Osafb3 and Osafb5 . The Ostir1Osafb2 double mutant displays extremely severe defects in plant development. All five OsTIR1/AFB members interacted with OsIAA1 and OsIAA11 proteins in vivo . Root elongation assay showed that each Ostir1/afb2–5 mutant was resistant to 2, 4‐dichlorophenoxyacetic acid (2, 4‐D) treatment. Notably, only the Osafb4 mutants were strongly resistant to the herbicide picloram, suggesting that OsAFB4 is a unique auxin receptor in rice. Our findings demonstrate similarities and specificities of auxin receptor TIR1/AFB proteins in rice, and could offer the opportunity to modify effective herbicide‐resistant alleles in agronomically important crops.