MtNODULE ROOT1 and MtNODULE ROOT2 Are Essential for Indeterminate Nodule Identity
MtNODULE ROOT1 and MtNODULE ROOT2 Are Essential for Indeterminate Nodule Identity
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DOI：
10.1104/pp.18.00610
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发表时间：
2018-09-01
期刊：
影响因子：
7.4
通讯作者：
Ratet, Pascal
中科院分区：
文献类型：
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作者：
Magne, Kevin;Couzigou, Jean-Malo;Ratet, Pascal
豆科植物和根瘤菌之间的共生相互作用导致固氮根瘤的形成，但对维持根瘤特性的分子因素和机制知之甚少。蒺藜苜蓿NOOT 1（MtNOOT 1）、豌豆COCHLEATA 1（PsCOCH 1）和百脉根NOOT-BOP-COCH-LIKE 1（LjNBCL 1）是拟南芥AtBLADE-ON-PETIOLE 1/2的直向同源物，并且是NBCL基因家族的成员，该基因家族在植物发育中具有保守的作用，并且对于豆科植物中的不确定和确定结节身份是必需的。MtNOOT 1、PsCOCH 1和LjNBCL 1功能的丧失触发了根瘤身份的部分丧失，其特征在于由根瘤维管分生组织产生的异位根的发育。在这里，我们报告了第二个基因的鉴定和特征，该基因参与调节M. truncatula，MtNOOT2. MtNOOT 2是MtNOOT 1的paradox，属于第二个豆类特异性NBCL亚支，NBCL 2 Glade。MtNOOT 2的表达在结节形成早期被诱导，并且主要在结节中央分生组织中表达。Mtnoot 2突变体没有任何特定的共生表型，然而，MtNOOT 1和MtNOOT 2的功能丧失导致根瘤身份的完全丧失，并伴随着共生，防御和根尖分生组织标记基因的表达发生急剧变化。Mtnoot 1 noot 2双突变体只开发nonfixing根状结构，不再能够宿主共生根瘤菌。这项研究提供了原始的见解，在豆科植物形成不确定的结节的根瘤身份的分子基础。
Symbiotic interactions between legume plants and rhizobia result in the formation of nitrogen-fixing nodules, but the molecular actors and the mechanisms allowing for the maintenance of nodule identity are poorly understood. Medicago truncatula NODULE ROOT1(MtNOOT1), Pisum sativum COCHLEATA1 (PsCOCH1), and Lotus japonicus NOOT-BOP-COCH-LIKE1 (LjNBCL1) are orthologs of Arabidopsis (Arabidopsis thaliana) AtBLADE-ON-PETIOLE1/2 and are members of the NBCL gene family, which has conserved roles in plant development and is essential for indeterminate and determinate nodule identity in legumes. The loss of function of MtNOOT1, PsCOCH1, and LjNBCL1 triggers a partial loss of nodule identity characterized by the development of ectopic roots arising from nodule vascular meristems. Here, we report the identification and characterization of a second gene involved in regulating indeterminate nodule identity in M. truncatula, MtNOOT2. MtNOOT2 is the paralog of MtNOOT1 and belongs to a second legume-specific NBCL subclade, the NBCL2 Glade. MtNOOT2 expression was induced during early nodule formation, and it was expressed primarily in the nodule central meristem. Mtnoot2 mutants did not present any particular symbiotic phenotype; however, the loss of function of both MtNOOT1 and MtNOOT2 resulted in the complete loss of nodule identity and was accompanied by drastic changes in the expression of symbiotic, defense, and root apical meristem marker genes. Mtnoot1 noot2 double mutants developed only nonfixing root-like structures that were no longer able to host symbiotic rhizobia. This study provides original insights into the molecular basis underlying nodule identity in legumes forming indeterminate nodules.