Achieving increased grain productivity has long been the overriding focus of cereal breeding programs. The ideotype approach has been used to improve rice yield potential at the International Rice Research Institute and in China. However, the genetic basis of yield-related traits in rice remains unclear. Here, we show that a major quantitative trait locus, qNPT1, acts through the determination of a 'new plant type' (NPT) architecture characterized by fewer tillers, sturdier culms and larger panicles, and it encodes a deubiquitinating enzyme with homology to human OTUB1. Downregulation of OsOTUB1 enhances meristematic activity, resulting in reduced tiller number, increased grain number, enhanced grain weight and a consequent increase in grain yield in rice. Unlike human OTUB1, OsOTUB1 can cleave both K48- and K63-linked polyubiquitin. OsOTUB1 interacts with the E2 ubiquitin-conjugating protein OsUBC13 and the squamosa promoter-binding protein-like transcription factor OsSPL14. OsOTUB1 and OsSPL14 share common target genes, and their physical interaction limits K63-linked ubiquitination (K63Ub) of OsSPL14, which in turn promotes K48Ub-dependent proteasomal degradation of OsSPL14. Conversely, loss-of-function of OsOTUB1 is correlated with the accumulation of high levels of OsSPL14, resulting in the NPT architecture. We also demonstrated that pyramiding of high-yielding npt1 and dep1-1 alleles provides a new strategy for increasing rice yield potential above what is currently achievable.
長久以來，提高糧食產(chǎn)量一直是谷物育種的首要目標。國際水稻研究所和中國已用理想株型來提高水稻產(chǎn)量潛能。然而，水稻產(chǎn)量相關性狀的遺傳基礎尚不清楚。在這里，我們發(fā)現(xiàn)一個主效QTL qNPT1，通過形成以較少分蘗，粗稈和大穗為特征的“新型”（NPT）水稻發(fā)揮作用，它編碼一個與人類OTUB1同源的去泛素化酶。下調(diào)OsOTUB1，能增強分生組織的活性，導致分蘗數(shù)減少，穗粒數(shù)增加，粒重增加，繼而水稻糧食產(chǎn)量增加。與人類OTUB1不同，OsOTUB1可以切割K48位多聚泛素和K63位多聚泛素。OsOTUB1與E2泛素結(jié)合蛋白OsUBC13和SPL家族轉(zhuǎn)錄因子OsSPL14互作。 OsOTUB1和OsSPL14有共同的靶基因，且它們的物理互作限制了OsSPL14的K63位多聚泛素化（K63Ub），反過來又促進OsSPL14的K48Ub依賴的蛋白酶體降解途徑。相反，OsOTUB1的功能缺失與OsSPL14大量積累相關，產(chǎn)生NPT株型。我們還表明，將高產(chǎn)npt1和dep1-1等位基因聚合，為在現(xiàn)有基礎上提高水稻產(chǎn)量潛能提供新的方法。