Rice (Oryza sativa) is the primary food source for more than one-half of the world’s population. Because rice cultivation is dependent on water availability, drought during flowering severely affects grain yield. Here, we show that the function of a drought-inducible receptor-like cytoplasmic kinase, named GROWTH UNDER DROUGHT KINASE (GUDK), is required for grain yield under drought and well-watered conditions. Loss-of-function gudk mutant lines exhibit sensitivity to salinity, osmotic stress, and abscisic acid treatment at the seedling stage, and a reduction in photosynthesis and plant biomass under controlled drought stress at the vegetative stage. The gudk mutants interestingly showed a significant reduction in grain yield, both under normal well-watered conditions and under drought stress at the reproductive stage. Phosphoproteome profiling of the mutant followed by in vitro assays identified the transcription factor APETALA2/ETHYLENE RESPONSE FACTOR OsAP37 as a phosphorylation target of GUDK. The involvement of OsAP37 in regulating grain yield under drought through activation of several stress genes was previously shown. Our transactivation assays confirmed that GUDK is required for activation of stress genes by OsAP37. We propose that GUDK mediates drought stress signaling through phosphorylation and activation of OsAP37, resulting in transcriptional activation of stress-regulated genes, which impart tolerance and improve yield under drought. Our study reveals insights around drought stress signaling mediated by receptor-like cytoplasmic kinases, and also identifies a primary regulator of grain yield in rice that offers the opportunity to improve and stabilize rice grain yield under normal and drought stress conditions.
水稻是世界上約一半人口的主食。因為水稻栽培對水的依賴極高，在開花階段的干旱會嚴重影響水稻產(chǎn)量。本文報道了一個干旱誘導(dǎo)的受體類細胞質(zhì)定位的激酶，GROWTH UNDER DROUGHT KINASE（GUDK），其功能對于干旱和灌水良好條件下的水稻谷粒產(chǎn)量至關(guān)重要。gudk功能缺失突變體在幼苗期表現(xiàn)出對鹽、滲透脅迫和脫落酸處理敏感，而營養(yǎng)生長階段在一定的干旱條件下光合作用能力和生物量降低。有趣的是，在生殖發(fā)育階段gudk突變體在正常水分充足和干旱脅迫條件下都表現(xiàn)出谷粒產(chǎn)量顯著降低的現(xiàn)象。基于體外研究方法對突變體進行磷酸蛋白組學(xué)分析發(fā)現(xiàn)了一個轉(zhuǎn)錄因子，APETALA2/ETHYLENE RESPONSE FACTOR OsAP37，是GUDK的一個磷酸化靶點。之前的研究表明OsAP37通過激活一些脅迫相關(guān)基因來調(diào)控干旱條件下谷粒產(chǎn)量。轉(zhuǎn)錄激活實驗表明GUDK是OsAP37激活這些脅迫相關(guān)基因所必需的。我們認為GUDK通過磷酸化和激活OsAP37來介導(dǎo)干旱脅迫的信號轉(zhuǎn)導(dǎo)，導(dǎo)致一些脅迫相關(guān)基因的轉(zhuǎn)錄被激活，它們的激活能夠提高脅迫耐性，從而在干旱條件下提高產(chǎn)量。我們的研究揭示了類受體胞質(zhì)激酶介導(dǎo)的干旱脅迫信號傳導(dǎo)途徑，鑒定了一個主要的水稻籽粒產(chǎn)量調(diào)控因子，提供了在正常和干旱條件下提高水稻產(chǎn)量的機遇。