Grain size and shape are important determinants of grain weight and yield in rice. Here, we report a new major quantitative trait locus (QTL), qTGW3, that controls grain size and weight in rice. This locus, qTGW3, encodes OsSK41 (also known as OsGSK5), a member of the GLYCOGEN SYNTHASE KINASE 3/SHAGGY-like family. Rice near-isogenic lines carrying the loss-of-function allele of OsSK41 have increased grain length and weight. We demonstrate that OsSK41 interacts with and phosphorylates AUXIN RESPONSE FACTOR 4 (OsARF4). Co-expression of OsSK41 with OsARF4 increases the accumulation of OsARF4 in rice protoplasts. Loss of function of OsARF4 results in larger rice grains. RNA-sequencing analysis suggests that OsARF4 and OsSK41 repress the expression of a common set of downstream genes, including some auxin-responsive genes, during rice grain development. The loss-of-function form of OsSK41 at qTGW3 represents a rare allele that has not been extensively utilized in rice breeding. Suppression of OsSK41 function by either targeted gene editing or QTL pyramiding enhances rice grain size and weight. Thus, our study reveals the important role of OsSK41 in rice grain development and provides new candidate genes for genetic improvement of grain yield in rice and perhaps in other cereal crops.
籽粒大小和形狀是決定水稻粒重和產(chǎn)量的重要因素。本文，我們報(bào)道了一個(gè)新的主效QTL qTGW3，控制水稻籽粒大小和重量。qTGW3位點(diǎn)編碼OsSK41（又名OsGSK5），屬于類GSK3/SHAGGY家族成員。攜帶OsSK41功能缺失等位基因的近等基因系，粒長(zhǎng)和粒重均增加。我們發(fā)現(xiàn)OsSK41能與生長(zhǎng)素抑制因子OsARF4互作并將其磷酸化。OsSK41與OsARF4共表達(dá)可增加OsARF4在水稻原生質(zhì)體中積累。OsARF4功能缺失導(dǎo)致水稻籽粒更大。RNA測(cè)序分析表明，在水稻籽粒發(fā)育過(guò)程中，OsARF4和OsSK41抑制了包括一些生長(zhǎng)素應(yīng)答基因在內(nèi)的一組常見(jiàn)下游基因的表達(dá)。qTGW3位點(diǎn)上功能喪失形式的OsSK41代表了一種罕見(jiàn)的等位基因，該等位基因尚未廣泛用于水稻育種。通過(guò)靶向基因編輯或QTL聚合抑制OsSK41的功能，可提高水稻的籽粒大小和重量。因此，我們的研究揭示了OsSK41在水稻籽粒發(fā)育中的重要作用，并為水稻和其他谷類作物的籽粒產(chǎn)量的遺傳改良提供了新的候選基因。