GRAS Transcription Factor WLG3 Regulates Grain Size and Weight in Rice.

Grain size is one of key agronomic trait that determines yield in rice (Oryza sativa L.). Several regulators of grain size have been identified in rice, but the mechanisms that determine this trait remain largely unknown. Here, we characterize the wlg3 mutant, which displays reduced plant height, shorter panicles, and larger grains than the wild type (WT). Genetic mapping and functional complementation identified WLG3 as a novel allele of DLT2, encoding a GRAS-type transcription factor that acts as a negative regulator of grain length and weight. WLG3 primarily controls grain size and shape by modulating cell proliferation in the spikelet hull. Integrated RNA‑seq and DAP‑seq analyses indicate that WLG3 directly binds and regulates genes involved in phenylpropanoid biosynthesis, amino sugar metabolism, and plant–pathogen interactions, thereby influencing grain development. Furthermore, we identified OsPUB43 as a candidate direct target of WLG3, suggesting that WLG3 may influence grain development, at least in part, through the potential regulation of OsPUB43 expression. Collectively, our findings expand the regulatory network controlling grain size and provide new insights into the role of GRAS transcription factors in grain development.