豆科植物-根瘤菌共生固氮是可持续性农业氮肥的最重要来源。根瘤作为豆科植物共生固氮的一种特化植物侧生器官, 提供了根瘤菌生物固氮必需的微环境, 是根瘤菌的安身之本, 因此, 根瘤的正常发育是实现豆科植物-根瘤菌共生固氮的结构基础。根瘤器官的从头发生主要起始于根瘤菌诱导的根皮层细胞分裂。通常认为豆科植物的根皮层具备有别于非豆科植物根皮层的某种特异属性, 从而响应根瘤菌并与之建立固氮共生, 但长期以来该属性决定的分子机制一直不明确。近日, 中国科学院分子植物科学卓越创新中心王二涛团队以蒺藜苜蓿(Medicago truncatula)等豆科植物和拟南芥(Arabidopsis thaliana)等非豆科植物为研究对象, 发现豆科植物中保守的SHR-SCR干细胞模块决定了其皮层细胞分裂潜能从而赋予根瘤器官发生的命运。该研究揭示了豆科植物根瘤发育的全新机制, 提供了研究和理解植物-根瘤菌固氮共生进化的重要线索, 对提高豆科作物固氮效率和非豆科作物固氮工程具有重要意义。

Symbiotic nitrogen fixation between legumes and rhizobia is the most important nitrogen source for sustainable agriculture. As the final accommodation for rhizobia, the specialized lateral organ, root nodule, that provides the essential microenvironments for rhizobia and its proper development, is vital for biological nitrogen fixation. Nodule de novo organogenesis mainly initiates from cortical cell division and it is generally accepted that cortical cells of legumes possess certain identity, which enables them to respond to and establish symbiosis with rhizobia, but the underlying mechanisms remain unknown. Recently a team led by Ertao Wang in Centre for Excellence in Molecular Plant Science, Chinese Academy of Science showed that the SHORTROOT-SCARECROW (SHR-SCR) module predetermines this cortical cell identity in legumes. This study uncovers a novel molecular mechanism for nodule organogenesis, and provides important clues for an evolutionary understanding of root nodule symbiosis, which is both practically and theoretically valuable for improving nitrogen fixation efficiency in legumes and engineering nitrogen symbiosis in non-legumes.