OsIAA19, an Aux/IAA Family Gene, Involved in the Regulation of Seed-Specific Traits in Rice

The Aux/IAA family proteins, key components of the auxin signaling pathway, are plant-specific transcription factors with important roles in regulating a wide range of plant growth and developmental events. The <i>Aux/IAA</i> family genes have been extensively studied in Arabidopsis. However, most of the <i>Aux/IAA</i> family genes in rice have not been functionally studied. Only two <i>IAA</i> genes have been reported to be involved in the regulation of rice grain size. Grain size is a key factor affecting both rice yield and quality. Therefore, we selected an unreported <i>IAA</i> member, <i>OsIAA19</i>, based on bioinformatics analysis to investigate its potential role in grain size control. Our study showed that <i>OsIAA19</i> was constitutively expressed in all tissues tested and that the encoding protein was nuclear localized. The <i>osiaa19</i> mutants were then generated using CRISPR/Cas9 gene editing. Agronomic trait analyses showed that the <i>OsIAA19</i> mutation significantly increased rice grain length and weight, but had no significant effect on plant height, number of tillers, flag leaf length and width. In addition, the chalkiness of the <i>osiaa19</i> mutant seeds also increased, but their eating and cooking quality (ECQ) was not altered. Finally, seed germination analysis showed that knocking out <i>OsIAA19</i> slightly suppressed rice seed germination. These results suggest that <i>OsIAA19</i> may specifically regulate rice seed-related traits, such as grain shape, rice chalkiness and seed germination. This study not only enriched the functional study of the <i>Aux/IAA</i> genes and the auxin signaling pathway in rice, but also provided valuable genetic resources for breeding elite rice varieties.