State Key Laboratory of Crop Stress Biology for Arid Areas and College of Life Sciences, Northwest Agriculture and Forestry University, Yangling, China.
Plant Cell Physiol. 2019 Apr 1;60(4):900-915. doi: 10.1093/pcp/pcz007.
The establishment of symbiosis between legume and rhizobium results in the formation of nodule. Phytocyanins (PCs) are a class of plant-specific blue copper proteins, playing critical roles in plant development including nodule formation. Although a few PC genes have been isolated from nodules, their functions are still unclear. Here, we performed a genome-wide identification of PC family in seven sequenced legume species (Medicago truncatula, Glycine max, Cicer arietinum, Cajanus cajan, Lotus japonicus, Vigna angularis and Phaseolus vulgaris) and found PCs experienced a remarkable expansion in M. truncatula and G. max. Further, we conducted an in-depth analysis of PC family in the model legume M. truncatula. Briefly, 82 MtPCs were divided into four subfamilies and clustered into seven clades, with a large proportion of tandem duplications and various cross-tissues expression patterns. Importantly, some PCs, such as MtPLC1, MtENODL27 and MtENODL28 were preferentially expressed in nodules. Further, RNA interference (RNAi) experiment revealed the knockdown of MtENDOL27 and MtENDOL28 impaired rhizobia infection, nodule numbers and nitrogenase activity. Moreover, in the MtENODL27-RNAi nodules, the infected cells were reduced and the symbiosomes did not reach the elongated stage, indicating MtENDOL27 is required for rhizobia infection and nodule development. In addition, co-expression analysis showed MtPLC1, MtENODL27 and MtENODL28 were grouped into two different functional modules and co-expressed with the known symbiotic nitrogen fixation-related genes, suggesting that they might participate in nodulation via different ways. In summary, this study provides a useful resource for future researches on the structure and function of PCs in nodulation.
豆科植物与根瘤菌之间共生关系的建立导致了根瘤的形成。植物细胞色素 c（PC）是一类植物特有的蓝色铜蛋白，在植物发育中起着关键作用，包括根瘤的形成。尽管已经从根瘤中分离出少数 PC 基因，但它们的功能仍不清楚。在这里，我们在 7 种已测序的豆科植物（蒺藜苜蓿、大豆、鹰嘴豆、豇豆、百脉根、野豌豆和菜豆）中进行了 PC 家族的全基因组鉴定，发现 PC 在蒺藜苜蓿和大豆中经历了显著扩张。此外，我们对模式豆科植物蒺藜苜蓿中的 PC 家族进行了深入分析。简要地说，82 个 MtPCs 分为四个亚家族，分为七个分支，具有大量的串联重复和各种跨组织表达模式。重要的是，一些 PC，如 MtPLC1、MtENODL27 和 MtENODL28，在根瘤中优先表达。此外，RNA 干扰（RNAi）实验表明，MtENODL27 和 MtENODL28 的敲低削弱了根瘤菌的侵染、根瘤数量和固氮酶活性。此外，在 MtENODL27-RNAi 根瘤中，感染细胞减少，共生体未达到伸长阶段，表明 MtENODL27 是根瘤菌侵染和根瘤发育所必需的。此外，共表达分析表明，MtPLC1、MtENODL27 和 MtENODL28 分为两个不同的功能模块，并与已知的共生固氮相关基因共表达，表明它们可能通过不同的方式参与结瘤。总之，本研究为进一步研究 PC 在结瘤中的结构和功能提供了有用的资源。
