研究找到调控水稻根系发生关键基因

中科院遗传与发育所植物基因组学国家重点实验室储成才课题组，通过大规模筛选水稻T-DNA插入突变体库，获得了一个水稻根数目显著增加的突变体，从而找到调控水稻根系发生的关键基因。相关成果近日在线发表于《植物生理学》杂志。

据了解，此突变体的表型由编码另一个细胞质型细胞分裂素氧化酶/脱氢酶基因OsCKX4被特异性激活而形成。OsCKX4受植物激素细胞分裂素和生长素的快速诱导，并在主根及冠根起始部位有较高表达。进一步研究发现，OsCKX4通过整合植物细胞分裂素和生长素两种激素信号途径，调控水稻冠根的起始，并与以前发现的在地上部分调控水稻穗粒数的另一细胞分裂素氧化酶/脱氢酶基因OsCKX2相得益彰。

储成才介绍说，细胞分裂素是植物的五大经典激素之一，在植物的生长发育中发挥重要作用。最新研究表明，不同类型的细胞分裂素氧化酶/脱氢酶可能参与植物不同的发育调控过程，从而分别在水稻穗发育过程中发挥重要作用，且通过不同细胞分裂素氧化酶对植物及地下根器官的发生过程产生重大影响。

该研究不仅加深了对细胞分裂素这一经典植物激素在植物生长发育中作用的理解，也为水稻及其他植物通过“根工程”改良营养吸收及非生物胁迫耐受性提供了极具潜力的靶标基因和思路。（来源：中国科学报 王静）

A cytokinin oxidase/dehydrogenase gene OsCKX4 integrates cytokinin and auxin signaling to control rice crown root formation

Abstract Crown roots constitute the majority of the rice root system, and play an important role in rice growth and development. However, the molecular mechanism of crown root formation in rice is still not well understood. Here, we characterized a rice dominant mutant, root enhancer1 (ren1-D), which was observed to exhibit a more robust root system, increased crown root number, and reduced plant height. Molecular and genetic analyses revealed that these phenotypes are caused by the activation of a cytokinin oxidase/dehydrogenase (CKX) family gene, OsCKX4. Subcellular localization demonstrated that OsCKX4 is a cytosolic isoform of CKX. OsCKX4 is predominantly expressed in leaf blades and roots, and it is the dominant CKX preferentially expressed in the shoot base where crown root primordia are produced, underlining its role in root initiation. OsCKX4 is induced by exogenous auxin and cytokinin in the roots. Furthermore, one-hybrid assays revealed that OsCKX4 is a direct binding target of both auxin response factor OsARF25 and the cytokinin response regulators ORR2 and ORR3. Overexpression and RNAi of OsCKX4 confirmed that OsCKX4 plays a positive role in crown root formation. Moreover, expression analysis revealed a significant alteration in the expression of auxin-related genes in the ren1-D mutants, indicating that the OsCKX4 mediates crown root development by integrating the interaction between cytokinin and auxin. Transgenic plants harboring OsCKX4 under the control of a root-specific promoter RCc3 displayed enhanced root development without affecting their shoot parts, suggesting that this strategy could be a powerful tool in rice root engineering.

原文链接：http://www.plantphysiol.org/content/early/2014/05/07/pp.114.238584.full.pdf+html

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