Abstract
Grain weight, a crucial trait that determines the grain yield in rice, is influenced by grain size. Although a series of regulators that control grain size have been identified in rice, the mechanisms underlying grain development are not yet well understood. In this study, we identified OsPUB43, a U-box E3 ubiquitin ligase, as an important negative regulator determining the gain size and grain weight in rice. Phenotypes of large grain are observed in ospub43 mutants, whereas overexpression of OsPUB43 results in short grains. Scanning electron microscopy analysis reveals that OsPUB43 modulates the grain size mainly by inhibiting cell proliferation in the spikelet hull. The OsPUB43 protein is localized in the cytoplasm and nucleus. The ospub43 mutants display high sensitivity to exogenous BR, while OsPUB43-OE lines are hyposensitive to BR. Furthermore, the transient transcriptional activity assay shows that OsBZR1 can activate the expression of OsPUB43. Collectively, our results indicate that OsPUB43 negatively controls the gain size by modulating the expression of BR-responsive genes as well as MADS-box genes that are required for lemma/palea specification, suggesting that OsPUB43 has a potential valuable application in the enlargement of grain size in rice.
Highlights
Rice (Oryza sativa L.), as one of the major yield crops in the world, provides food for more than half of the world’s population [1–4]
Studies in Arabidopsis and rice indicated that seed size is modulated by multiple signaling pathways and regulators, including the HAIKU (IKU) pathway, the ubiquitin–proteasome pathway (UPP), phytohormones signaling, mitogen-activated protein kinase (MAPK) signaling, Gprotein signaling (RGS), and numerous transcriptional regulatory factors [11–15]
To reveal the regulatory function of U-box E3 ubiquitin ligase in the seed development in rice, we analyzed the spatio-temporal expression profile for a subset of U-box E3 ubiquitin ligase genes by the PlaNet and GENEVESTIGATOR tools [59,60], found that OsPUB43 (LOC_Os02g34410) was preferentially expressed in the inflorescence or panicle (Figure S1)
Summary
Rice (Oryza sativa L.), as one of the major yield crops in the world, provides food for more than half of the world’s population [1–4]. The ubiquitin receptor HDR3 forms a complex with GW6a, and the transgenic rice plants overexpressing HDR3 and GW6a have a larger grain than the wild type, indicating that both of them play a positive role in the spikelet hull cell proliferation [36,37]. (Ubiquitin-Specific Protease 15) acts as an active regulator of grain width and size, and the dominant gain-of-function rice mutant lg1-D of OsUBP15 shows the enhanced cell proliferation in the spikelet hull [38]. The elf mutant was a visibly shorter and smaller grain than the wild type [48], which is similar to BR-deficient mutant brd (BRdeficient dwarf2) and BR receptor mutant d61 (brassinosteroid insensitive, osbriI), indicating that the E3 ubiquitin ligase ELF1 plays a critical role in BR signaling in rice [39,49–51]. Our findings defined OsPUB43 as a critical factor that determined grain size and weight, suggesting its potential value in increasing rice yield
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
