Functional Analysis of the Autophagy-Related Gene OsATG4b in Rice Grain Chalkiness Regulation

Grain chalkiness is an undesirable trait that significantly compromises rice quality, attracting considerable attention from both consumers and breeders. In this study, we characterized the role of the autophagy-related gene <i>OsATG4b</i> in rice grain development. <i>OsATG4b</i> was predominantly expressed in the endosperm. Compared with wild-type plants, <i>OsATG4b</i>-overexpressing lines exhibited significantly reduced grain chalkiness, whereas <i>OsATG4b</i> knockout mutants displayed a marked increase in chalkiness. Importantly, <i>OsATG4b</i> had no significant effect on other major agronomic traits. Ultrastructure analysis of the endosperm and evaluation of seed storage components revealed that the chalky endosperm in <i>OsATG4b</i> Knockout mutants contained loosely packed starch granules, aberrant protein bodies, and reduced levels of seed storage proteins. Furthermore, gene expression analysis indicated that <i>OsATG4b</i> regulates the expression of genes involved in storage protein biosynthesis. Together, these findings demonstrate that <i>OsATG4b</i> plays a critical regulatory role in determining grain chalkiness in rice.