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.
长久以来，提高粮食产量一直是谷物育种的首要目标。国际水稻研究所和中国已用理想株型来提高水稻产量潜能。然而，水稻产量相关性状的遗传基础尚不清楚。在这里，我们发现一个主效QTL qNPT1，通过形成以较少分蘖，粗秆和大穗为特征的“新型”（NPT）水稻发挥作用，它编码一个与人类OTUB1同源的去泛素化酶。下调OsOTUB1，能增强分生组织的活性，导致分蘖数减少，穗粒数增加，粒重增加，继而水稻粮食产量增加。与人类OTUB1不同，OsOTUB1可以切割K48位多聚泛素和K63位多聚泛素。OsOTUB1与E2泛素结合蛋白OsUBC13和SPL家族转录因子OsSPL14互作。 OsOTUB1和OsSPL14有共同的靶基因，且它们的物理互作限制了OsSPL14的K63位多聚泛素化（K63Ub），反过来又促进OsSPL14的K48Ub依赖的蛋白酶体降解途径。相反，OsOTUB1的功能缺失与OsSPL14大量积累相关，产生NPT株型。我们还表明，将高产npt1和dep1-1等位基因聚合，为在现有基础上提高水稻产量潜能提供新的方法。