近年来由于极端气候频繁出现，作物穗发芽现象已呈现普遍递增的态势，即使在黑龙江寒带水稻生产区，穗发芽也呈现上升势头。穗发芽是影响水稻、小麦等主要农作物产量和品质的重要因素之一。为此中国科学院东北地理与农业生态研究所与东北农业大学等单位合作，在黑龙江省杰出青年基金及国家重点研发计划的资助下，成功鉴定克隆了两个水稻钼辅因子（MoCo）合成基因，并揭示MoCo合成途径在调节水稻穗发芽及胁迫耐受性过程中发挥关键作用。

东北地理所水稻分子育种学科组研究员方军前期通过大规模的筛选，获得一系列水稻穗发芽突变体，并克隆了其中的PHS1-PHS4 和PHS8基因（Plant J， 2008、Plant J，2018）。本次研究证明了MoCo合成基因OsCNX1 和OsCNX6 的突变最终导致了穗发芽及纯合致死。OsCNX6 编码MoCo合成蛋白2大亚基，该基因的突变导致黄嘌呤脱氢酶（XDH）、醛氧化酶（AO）、硝酸还原酶（NR）及亚硫酸盐氧化酶（SO）等四种钼酶活性显着降低。通过分析基因表达模式，表明OsCNX6在水稻的叶片、茎秆、胚乳等部位均有表达。进一步过量表达该基因的转基因水稻没有出现不利的农艺性状，而植株对渗透和盐胁迫的抗性有了显着提高。这一研究不仅揭示了MoCo合成基因对水稻生长发育的重要作用，同时也为水稻抗逆育种提供了新的研究思路和视角，具有重要的理论和应用价值。

该研究成果于11月24日在线发表于New Phytologist 杂志。东北农业大学农学院讲师刘鑫与东北地理所博士后王晶为该论文共同第一作者。方军为论文通讯作者。(中国科学院东北地理与农业生态研究所）

Identification and characterization of the rice pre‐harvest sprouting mutants involved in molybdenum cofactor biosynthesis

Abstract  In cereal crops, ABA deficiency during seed maturation phase causes pre‐harvest sprouting (PHS), and molybdenum cofactor (MoCo) is required for ABA biosynthesis. Here, two rice PHS mutants F254 and F5‐1 were characterized. In addition to the PHS, these mutants showed pleiotropic phenotypes such as twisting and slender leaves, and then died when the seedling developed to four or five leaves. Map‐based cloning showed that OsCNX6 and OsCNX1 encoding homologs of MoaE and MoeA were responsible for F254 and F5‐1 mutants, respectively. Genetic complementation indicated that OsCNX6 not only rescued the PHS and seedling lethal phenotype of cnx6 mutant, but also recovered the MoCo‐dependent enzyme activities such as xanthine dehydrogenase (XDH), aldehyde oxidase (AO), nitrate reductase (NR), and sulfite oxidase (SO). Expression pattern showed that OsCNX6 was richly expressed in seed during embryo maturation by qRT‐PCR and RNA in situ hybridization. Furthermore, the OsCNX6overexpression plants can significantly enhance the MoCo‐dependent enzyme activities, and improved the osmotic and salt stress tolerance without unfavorable phenotypes. Collectively, these data described that OsCNX6 participated in MoCo biosynthesis, and is essential for rice development, especially for seed dormancy and germination, and OsCNX6 could be an effective target for improving abiotic stress tolerance in rice.

原文链接：https://nph.onlinelibrary.wiley.com/doi/epdf/10.1111/nph.15607