Grain size is an important determinant of yield potential in crops. We previously demonstrated that natural mutations in the regulatory sequences of qSW5/GW5 confer grain width diversity in rice. However, the biological function of a GW5 homolog, named GW5‐Like (GW5L), remains unknown. In this study, we report on GW5L knockout mutants in Kitaake, a japonica cultivar (cv.) considered to have a weak gw5 variant allele that confers shorter and wider grains. GW5L is evenly expressed in various tissues, and its protein product is localized to the plasma membrane. Biochemical assays verified that GW5L functions in a similar fashion to GW5. It positively regulates brassinosteroid (BR) signaling through repression of the phosphorylation activity of GSK2. Genetic data show that GW5L overexpression in either Kitaake or a GW5 knockout line, Kasaorf3 (indica cv. Kasalath background), causes more slender, longer grains relative to the wild‐type. We also show that GW5L could confer salt stress resistance through an association with calmodulin protein OsCaM1‐1. These findings identify GW5L as a negative regulator of both grain size and salt stress tolerance, and provide a potential target for breeders to improve grain yield and salt stress resistance in rice.
籽粒大小是決定作物產(chǎn)量潛力的重要因素。我們先前已經(jīng)證實(shí)qSW5/GW5調(diào)控序列的自然變異導(dǎo)致了水稻的粒寬多樣性。然而，GW5同源基因GW5‐Like (GW5L)的生物學(xué)功能尚不清楚。在本研究中，我們報(bào)道了一個(gè)粳稻品種Kitaake的GW5L基因敲除突變體，該品種被認(rèn)為具有一個(gè)弱的gw5變異等位基因，可以產(chǎn)生較短和較寬的籽粒。GW5L在多種組織中均表達(dá)，其蛋白產(chǎn)物定位于質(zhì)膜。生化分析證實(shí)GW5L的功能與GW5相似。它通過抑制GSK2的磷酸化活性來(lái)正向調(diào)節(jié)油菜素類固醇（BR）信號(hào)。遺傳數(shù)據(jù)顯示，GW5L在Kitaake或GW5敲除系（Kasaorf3，秈稻Kasalath背景）中過表達(dá)，產(chǎn)生了相對(duì)于野生型更細(xì)長(zhǎng)的籽粒。我們還發(fā)現(xiàn)GW5L通過與鈣調(diào)素蛋白OsCaM1-1的結(jié)合而具有抗鹽性。這些發(fā)現(xiàn)表明GW5L是水稻籽粒大小和耐鹽性的負(fù)調(diào)控因子，為育種工作者提高水稻產(chǎn)量和抗鹽性提供了一個(gè)潛在的靶點(diǎn)。