Functional analysis of auxin receptor OsTIR1/OsAFB family members in rice grain yield, tillering, plant height, root system, germination, and auxinic herbicide resistance

Abstract

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.

The Lotus japonicus AFB6 Gene Is Involved in the Auxin Dependent Root Developmental Program

“…The main phenotypic trait reported in the A. thaliana tir1, afb1, afb2, afb3, afb4 and afb5 single mutant backgrounds was increased primary root growth in the presence of auxin, whereas they appeared similar to wild type plants in standard laboratory conditions of growth [11,17,18,36,47,48,53]. An increased root elongation tolerance in the presence of 2,4-D was recently reported also in O. sativa tir1/afb single mutants [19].…”

“…In species other than A. thaliana, the investigation of the TIR1/AFB auxin receptor family has been quite limited. Very recently the functional characterization of the Oryza sativa TIR1/AFB family was reported [19]. The O. sativa members maintain the capacity to physically interact with IAA proteins, and single mutants display a mild resistance to exogenous auxin and partially redundant phenotypes in grain yield, tillering, plant height, root system and germination [19].…”

Fine-mapping and candidate gene analysis of a major locus controlling leaf thickness in rice (Oryza sativa L.)

“…There are about 687 potential F-box proteins in rice controlling the degradation of cellular proteins in rice (Paterson et al 1993 ). Some of them encoded phytohormone important signaling transduction regulators, such as TIR1 , COI1 , GID2 , and MAX2 (Tao et al 2017 ; Guo et al 2021 ; Liu et al 2021 ; Patil et al 2021 ). Moreover, a small beta-glucosidase cluster is also presented in the candidate region.…”

Rice LEAFY COTYLEDON1 hinders photosynthesis in the embryo development to promote seed dormancy

“…For subcellular co-localisation of proteins, the coding sequence, not including the stop codon of OsLEC1, was cloned into the pUGW5 vector to generate the 35S:OsLEC1-GFP via LR Clonase reactions according to the manufacturer's instructions. The 35S:OsIAA1-mcherry vector has been described previously (49). The primers used are listed in Supplementary Table 15.…”