Liao Xiong, Guo Xiao, Wang Qi, Wang Yantao, Zhao Di, Yao Liping, Wang Shuang, Liu Guojie, Li Tianhong
Department of Pomology, College of Horticulture, China Agricultural University, Beijing, 100193, China.
College of Food Science and Engineering, Shandong Agricultural University, Taian, 271018, China.
Plant J. 2017 Feb;89(3):510-526. doi: 10.1111/tpj.13401. Epub 2017 Feb 1.
Dehydration-responsive element binding factors (DREBs) play important roles in plant growth, development, and stress signaling pathways in model plants. However, little is known about the function of DREBs in apple (Malus × domestica), a widely cultivated crop that is frequently threatened by drought. We isolated a DREB gene from Malus sieversii (Ledeb.) Roem., MsDREB6.2, and investigated its functions using overexpression analysis and chimeric repressor gene-silencing technology (CRES-T). We identified possible target genes of the protein encoded by MsDREB6.2 using electrophoretic mobility shift assays (EMSAs) and chromatin immunoprecipitation (ChIP). Overexpression of MsDREB6.2 increased the expression of a key cytokinin (CK) catabolism gene, MdCKX4a, which led to a significant reduction in endogenous CK levels, and caused a decrease in shoot:root ratio in transgenic apple plants. Overexpression of MsDREB6.2 resulted in a decrease in stomatal aperture and density and an increase in root hydraulic conductance (L ), and thereby enhanced drought tolerance in transgenic plants. Furthermore, manipulating the level of MsDREB6.2 expression altered the expression of two aquaporin (AQP) genes. The effect of the two AQP genes on L was further characterized using the AQP inhibitor HgCl . Based on these observations, we conclude that MsDREB6.2 enhances drought tolerance and that its function may be due, at least in part, to its influence on stomatal opening, root growth, and AQP expression. These results may have applications in apple rootstock breeding programs aimed at developing drought-resistant apple varieties.
脱水响应元件结合因子（DREB）在模式植物的生长、发育及胁迫信号通路中发挥着重要作用。然而，对于苹果（Malus × domestica）这种广泛种植且常受干旱威胁的作物中DREB的功能却知之甚少。我们从新疆野苹果（Malus sieversii (Ledeb.) Roem.）中分离出一个DREB基因MsDREB6.2，并通过过表达分析和嵌合抑制基因沉默技术（CRES-T）研究了其功能。我们利用电泳迁移率变动分析（EMSA）和染色质免疫沉淀（ChIP）鉴定了MsDREB6.2编码蛋白的可能靶基因。MsDREB6.2的过表达增加了关键细胞分裂素（CK）分解代谢基因MdCKX4a的表达，这导致内源CK水平显著降低，并使转基因苹果植株的地上部与地下部比值下降。MsDREB6.2的过表达导致气孔孔径和密度减小，根系水力导度（L）增加，从而增强了转基因植株的耐旱性。此外，调控MsDREB6.2的表达水平会改变两个水通道蛋白（AQP）基因的表达。使用AQP抑制剂HgCl进一步表征了这两个AQP基因对L的影响。基于这些观察结果，我们得出结论，MsDREB6.2增强了耐旱性，其功能可能至少部分归因于它对气孔开放、根系生长和AQP表达的影响。这些结果可能应用于旨在培育抗旱苹果品种的苹果砧木育种计划。
