title: Overexpression of MsDREB6.2 results in cytokinin-deficient developmental phenotypes and enhances drought tolerance in transgenic apple plants.
abstract: 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 (L0), 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 L0was further characterized using the AQP inhibitor HgCl2. 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.
authors.affiliation: Department of Pomology, College of Horticulture, China Agricultural University, Beijing, 100193, China.
authors.forename: Xiong
authors.initials: X
authors.lastname: Liao
authors.affiliation: Department of Pomology, College of Horticulture, China Agricultural University, Beijing, 100193, China.
authors.forename: Xiao
authors.initials: X
authors.lastname: Guo
authors.affiliation: College of Food Science and Engineering, Shandong Agricultural University, Taian, 271018, China.
authors.forename: Qi
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Department of Pomology, College of Horticulture, China Agricultural University, Beijing, 100193, China.
authors.forename: Yantao
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Pomology, College of Horticulture, China Agricultural University, Beijing, 100193, China.
authors.forename: Di
authors.initials: D
authors.lastname: Zhao
authors.affiliation: Department of Pomology, College of Horticulture, China Agricultural University, Beijing, 100193, China.
authors.forename: Liping
authors.initials: L
authors.lastname: Yao
authors.affiliation: Department of Pomology, College of Horticulture, China Agricultural University, Beijing, 100193, China.
authors.forename: Shuang
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Pomology, College of Horticulture, China Agricultural University, Beijing, 100193, China.
authors.forename: Guojie
authors.initials: G
authors.lastname: Liu
authors.affiliation: Department of Pomology, College of Horticulture, China Agricultural University, Beijing, 100193, China.|Beijing Collaborative Innovation Center for Eco-environmental Improvement with Forestry and Fruit Trees, Beijing, 102206, China.
authors.forename: Tianhong
authors.initials: T
authors.lastname: Li
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics; D020346:Aquaporins / Q000235:genetics / Q000378:metabolism; D003583:Cytokinins / Q000378:metabolism*; D055864:Droughts; D018507:Gene Expression Regulation, Developmental; D018506:Gene Expression Regulation, Plant; D027845:Malus / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D018517:Plant Roots / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D018520:Plant Shoots / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D054046:Plant Stomata / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D030821:Plants, Genetically Modified; D011485:Protein Binding; D013312:Stress, Physiological
chemical_list: D020346:Aquaporins; D003583:Cytokinins; D010940:Plant Proteins
keywords: CRES-T; DREB6-type transcription factor; Malus sieversii Roem; aquaporin; cytokinin; drought stress; root hydraulic conductance; shoot:root ratio