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 Aux/IAA family genes have been extensively studied in Arabidopsis. However, most of the Aux/IAA family genes in rice have not been functionally studied. Only two IAA 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 IAA member, OsIAA19, based on bioinformatics analysis to investigate its potential role in grain size control. Our study showed that OsIAA19 was constitutively expressed in all tissues tested and that the encoding protein was nuclear localized. The osiaa19 mutants were then generated using CRISPR/Cas9 gene editing. Agronomic trait analyses showed that the OsIAA19 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 osiaa19 mutant seeds also increased, but their eating and cooking quality (ECQ) was not altered. Finally, seed germination analysis showed that knocking out OsIAA19 slightly suppressed rice seed germination. These results suggest that OsIAA19 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 Aux/IAA genes and the auxin signaling pathway in rice, but also provided valuable genetic resources for breeding elite rice varieties.