WIDE AND THICK GRAIN 1, which encodes an otubain‐like protease with deubiquitination activity, influences grain size and shape in rice

Abstract

Grain size and shape are two crucial traits that influence grain yield and grain appearance in rice. Although several factors that affect grain size have been described in rice, the molecular mechanisms underlying the determination of grain size and shape are still elusive. In this study we report that WIDE AND THICK GRAIN 1 (WTG1) functions as an important factor determining grain size and shape in rice. The wtg1-1 mutant exhibits wide, thick, short and heavy grains and also shows an increased number of grains per panicle. WTG1 determines grain size and shape mainly by influencing cell expansion. WTG1 encodes an otubain-like protease, which shares similarity with human OTUB1. Biochemical analyses indicate that WTG1 is a functional deubiquitinating enzyme, and the mutant protein (wtg1-1) loses this deubiquitinating activity. WTG1 is expressed in developing grains and panicles, and the GFP-WTG1 fusion protein is present in the nucleus and cytoplasm. Overexpression of WTG1 results in narrow, thin, long grains due to narrow and long cells, further supporting the role of WTG1 in determining grain size and shape. Thus, our findings identify the otubain-like protease WTG1 to be an important factor that determines grain size and shape, suggesting that WTG1 has the potential to improve grain size and shape in rice.

A reductionist approach to dissecting grain weight and yield in wheat

“…Genes involved in the ubiquitin pathway are also important regulators of grain weight in many plant species, including GW2 (reviewed in Li and Li ). Genes with deubiquitinating activity have also been shown to influence seed size, such as WIDE AND THICK GRAIN 1 ( WTG1 ) in rice and UBIQUITIN SPECIFIC PROTEASE 15 ( UBP15 ) in Arabidopsis , which act as negative and positive regulators of seed size, respectively (Du et al ; Huang et al ). Genes involved with phytohormone signaling are also important regulators of seed size, with roles being demonstrated for auxin, brassinosteroid and cytokinin biosynthesis and signaling components (Riefler et al ; Schruff et al ; Jiang et al ).…”

The rice PLATZ protein SHORT GRAIN6 determines grain size by regulating spikelet hull cell division

“…Studies have also shown that UPS also participates in the control of seed size; for example, GRAIN WIDTH2 (GW2, a RING‐type protein) functions as an E3 ubiquitin ligase for rice expansin‐like 1 in the UPS pathway and negatively regulates grain size and weight (Song et al 2007; Choi et al 2018). WIDE AND THICK GRAIN1 ( WTG1 ) encodes an otubain‐like protease with deubiquitination activity, which determines grain size and shape mainly by influencing cell expansion (Huang et al 2017).…”

New path towards a better rice architecture

“…Second, similar phenotypes were observed in plants with disrupted OsOTUB1 function by CRISPR/Cas9. Third, Huang et al [5] also recently reported the null allele mutant (wtg1) of OsOTUB1 and the same grain phenotypes as OsOTUB1 loss-of-function mutants were observed, further confirming that OsOTUB1 negatively regulates these traits. In contrast, OsOTUB1 overexpression induced aberrant phenotypes such as dwarfism, malformed panicle with decreased grain number, necrotic leaves, and decreased tiller number per plant, which are not completely opposite to the phenotypes of the loss-of-function mutants, and thus, may indicate the side-effect of OsOTUB1 overproduction.…”