The identification and characterization of a plant height and grain length related gene hfr131 in rice

Abstract

Plant height and grain size are important agronomic traits affecting rice yield. Various plant hormones participate in the regulation of plant height and grain size in rice. However, how these hormones cooperate to regulate plant height and grain size is poorly understood. In this study, we identified a brassinosteroid-related gene, <i>hfr131</i>, from an introgression line constructed using <i>Oryza longistaminata</i>, that caused brassinosteroid insensitivity and reduced plant height and grain length in rice. Further study showed that <i>hfr131</i> is a new allele of <i>OsBRI1</i> with a single-nucleotide polymorphism (G to A) in the coding region, leading to a T988I conversion at a conserved site of the kinase domain. By combining yeast one-hybrid assays, chromatin immunoprecipitation-quantitative PCR and gene expression quantification, we demonstrated that OsARF17, an auxin response factor, could bind to the promoter region of <i>HFR131</i> and positively regulated <i>HFR131</i> expression, thereby regulating the plant height and grain length, and influencing brassinosteroid sensitivity. Haplotype analysis showed that the consociation of <i>OsAFR17^Hap1</i> /<i>HFR131^Hap6</i> conferred an increase in grain length. Overall, this study identified <i>hfr131</i> as a new allele of <i>OsBRI1</i> that regulates plant height and grain length in rice, revealed that brassinosteroid and auxin might coordinate through <i>OsARF17</i>-<i>HFR131</i> interaction, and provided a potential breeding target for improvement of rice yield.