Cheng Yanxia, Wang Qiao, Yang Linxi, Li Quanzi, Yan Xiaojing
State Key Laboratory of Tree Genetics and Breeding, Chinese Academy of Forestry, Beijing 100091, China.
College of Resources and Environment, Qingdao Agricultural University, Qingdao, Shandong 266109, China.
Hortic Res. 2024 Jun 7;11(8):uhae157. doi: 10.1093/hr/uhae157. eCollection 2024 Aug.
Maintenance of intracellular ion balance, especially Na and K, plays an important role in plant responses to salt stress. Vessels in xylem are responsible for long-distance ion transport in vascular plants. Knowledge on the salt stress response in woody plants in limited. In this study, we identified miR319a as an important regulator in respond to salt stress in poplar. miR319a overexpression transgenic poplar showed a salt-tolerant phenotype, and cytological observation showed reduced cambium cell layers, wider xylem, increased number and lumen area of vessels and fibers, and thinner cell wall thickness in the transgenics. The miR319a-MIMIC plants, meanwhile, had opposite phenotypes, with narrower xylem, reduced number and lumen area of vessels and fibers cells, and increased wall thickness. In addition, overexpression of miR319a driven by the vessel-specific promoter significantly improved the salt tolerance compared with the fiber-specific promoter. The expression levels of and , which encoded high-affinity K and Na transporters for Na efflux and K influx, respectively, were positively correlated with the vessel number and lumen area. These results suggest that miR319 not only promotes ion transport rates by increasing vessel number and lumen area and reducing cell wall thickness, but also regulates the concentrations of Na and K in the xylem by up-regulating and . We demonstrate that miR319 may coordinate the response of poplar to salt stress through both mechanisms, enriching our understanding of the synergistic effects of the secondary xylem structure and long-distance ion transport balance in the salt tolerance of poplar.
维持细胞内离子平衡，尤其是钠和钾的平衡，在植物对盐胁迫的响应中起着重要作用。木质部中的导管负责维管植物中的长距离离子运输。关于木本植物盐胁迫响应的知识有限。在本研究中，我们鉴定出miR319a是杨树对盐胁迫响应中的一个重要调节因子。过表达miR319a的转基因杨树表现出耐盐表型，细胞学观察显示转基因杨树的形成层细胞层数减少、木质部变宽、导管和纤维的数量及管腔面积增加，细胞壁厚度变薄。同时，miR319a-MIMIC植物具有相反的表型，木质部变窄、导管和纤维细胞的数量及管腔面积减少，细胞壁厚度增加。此外，与纤维特异性启动子驱动的miR319a过表达相比，由导管特异性启动子驱动的miR319a过表达显著提高了耐盐性。分别编码用于钠外流和钾内流的高亲和力钾和钠转运蛋白的 和 的表达水平与导管数量和管腔面积呈正相关。这些结果表明，miR319不仅通过增加导管数量和管腔面积以及减少细胞壁厚度来提高离子运输速率，还通过上调 和 来调节木质部中钠和钾的浓度。我们证明miR319可能通过这两种机制协调杨树对盐胁迫的响应，丰富了我们对次生木质部结构和长距离离子运输平衡在杨树耐盐性中的协同作用的理解。
