Knockdown of LjIPT3 influences nodule development in Lotus japonicus
Knockdown of LjIPT3 influences nodule development in Lotus japonicus
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LjIPT3 的敲除影响百脉根瘤的发育。
DOI：
10.1093/pcp/pct171
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发表时间：
2014-01-01
影响因子：
4.9
通讯作者：
Wu, Guojiang
中科院分区：
文献类型：
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作者：
Chen, Yaping;Chen, Wei;Wu, Guojiang
细胞分裂素在豆科植物与根瘤菌共生过程中起着重要作用。在这里，我们报告分离的六个基因编码异戊烯基转移酶（IPT）从百脉根，催化限速步骤的细胞分裂素的生物合成。发现LjIPT 3基因在感染的根和成熟的根瘤中上调。组织化学分析表明，Pro（LjIPT 3）：GUS（β-葡萄糖醛酸酶）在营养和生殖器官的表达，尤其是在根的维管束。当接种中慢生根瘤菌MAFF 303099时，LjIPT 3在根瘤原基和发育中的根瘤中检测不到，随后仅在成熟根瘤的维管束中表达。此外，敲低LjIPT 3（LjIPT 3 i）的RNA干扰降低内源细胞分裂素的水平，影响植物的发育和加速叶绿素降解在黑暗诱导的叶片衰老。与野生型相比，LjIPT 3 i植株产生更少的侵染丝和根瘤。此外，下游结瘤相关转录因子基因LjNSP 1、LjNSP 2和LjNIN在LjIPT 3 i植物中的表达急剧下降。这些结果表明，LjIPT 3调节CRE 1依赖性细胞分裂素途径，影响结节的起始，从而影响感染线和结节的数量。固氮酶活性检测和根瘤结构观察表明，内源细胞分裂素是成熟根瘤中受感染细胞充分发育所必需的，可以防止早衰。因此，我们的研究结果表明，LjIPT 3基因产物是结节的起始和发展所需的，并且似乎不参与早期感染事件。
Cytokinins play important roles in legume-rhizobia symbiosis. Here we report isolation of six genes encoding isopentenyl transferase (IPT) from Lotus japonicus, which catalyze the rate-limiting step of cytokinin biosynthesis. The LjIPT3 gene was found to be up-regulated in infected roots and mature nodules. Histochemical analysis demonstrated expression of Pro(LjIPT3):GUS (beta-glucuronidase) in vegetative and reproductive organs, and was especially high in the vascular bundles of roots. When inoculated with Mesorhizobium loti MAFF303099, LjIPT3 was undetectable in the nodule primordia and developing nodules, and later it was expressed only in the vascular bundles of mature nodules. In addition, knockdown of LjIPT3 (LjIPT3i) by RNA interference reduced levels of endogenous cytokinins, affected plant development and accelerated Chl degradation during dark-induced leaf senescence. Compared with the wild type, LjIPT3i plants produced fewer infection threads and nodules. In addition, expression of downstream nodulation-related transcription factor genes LjNSP1, LjNSP2 and LjNIN decreased dramatically in LjIPT3i plants. These results suggest that LjIPT3 regulates the CRE1-dependent cytokinin pathway, affecting nodule initiation and thereby influencing the number of infection threads and nodules. Detection of nitrogenase activity and observation of nodule structure showed that endogenous cytokinins are required for full development of the infected cells in mature nodules by preventing early senescence. Therefore, our results indicate that the LjIPT3 gene product is required for nodule initiation and development, and does not appear to be involved in early infection events.