College of Horticulture, Nanjing Agricultural University, Nanjing, 210095, Jiangsu, China.
Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, 210014, Jiangsu, China.
BMC Plant Biol. 2020 May 7;20(1):194. doi: 10.1186/s12870-020-02378-4.
The mitogen-activated protein kinases (MAPKs), as a part of the MAPKKK-MAPKK-MAPK cascade, play crucial roles in plant development as an intracellular signal transduction pathway to respond various environmental signals. However, few MAPKK have been functionally characterized in grapevine.
In the study, five MAPKK (MKK) members were identified in grapevine (cultivar 'Pinot Noir'), cloned and designated as VvMKK1-VvMKK5. A phylogenetic analysis grouped them into four sub-families based on the similarity of their conserved motifs and gene structure to Arabidopsis MAPKK members. qRT-PCR results indicated that the expression of VvMKK1, VvMKK2, VvMKK4, and VvMKK5 were up-regulated in mature leaf and young blades, and roots, but exhibited low expression in leaf petioles. VvMKK2, VvMKK3, and VvMKK5 genes were differentially up-regulated when grapevine leaves were inoculated with spores of Erisyphe necator, or treated with salicylic acid (SA), ethylene (ETH), HO or exposed to drought, indicating that these genes may be involved in a variety of signaling pathways. Over expression of VvMKK2 and VvMKK4 genes in transgenic Arabidopsis plants resulted in the production of seeds with a significantly higher germination and survival rate, and better seedling growth under stress conditions than wild-type plants. Overexpression of VvMKK2 in Arabidopsis improved salt and drought stress tolerance while overexpression of VvMKK4 only improved salt stress tolerance.
Results of the present investigation provide a better understanding of the interaction and function of MAPKKK-MAPKK-MAPK genes at the transcriptional level in grapevine and led to the identification of candidate genes for drought and salt stress in grapes.
丝裂原活化蛋白激酶（MAPKs）作为 MAPKKK-MAPKK-MAPK 级联反应的一部分，作为一种细胞内信号转导途径，在植物发育中发挥着重要作用，以响应各种环境信号。然而，在葡萄中，仅有少数 MAPKK 被功能表征。
本研究在葡萄（品种‘黑比诺’）中鉴定并克隆了 5 个 MAPKK（MKK）成员，命名为 VvMKK1-VvMKK5。基于其保守基序和基因结构与拟南芥 MAPKK 成员的相似性，系统发育分析将它们分为四个亚家族。qRT-PCR 结果表明，VvMKK1、VvMKK2、VvMKK4 和 VvMKK5 在成熟叶片和幼叶以及根中表达上调，但在叶片叶柄中表达较低。当葡萄叶片接种白粉菌孢子或用水杨酸（SA）、乙烯（ETH）、HO 处理或暴露于干旱时，VvMKK2、VvMKK3 和 VvMKK5 基因表达差异上调，表明这些基因可能参与多种信号通路。VvMKK2 和 VvMKK4 基因在转基因拟南芥植物中的过表达导致种子的萌发和存活率显著提高，在胁迫条件下幼苗生长更好，而野生型植物则没有。VvMKK2 在拟南芥中的过表达提高了盐和干旱胁迫耐受性，而过表达 VvMKK4 仅提高了盐胁迫耐受性。
本研究结果更好地了解了葡萄中 MAPKKK-MAPKK-MAPK 基因在转录水平上的相互作用和功能，并鉴定了葡萄中干旱和盐胁迫的候选基因。
