Jingjing Yang;Ruiling Zhan;Lan Wang;Junqiao Li;Baiquan Ma;Fengwang Ma;Mingjun L

Key Laboratory of Molecular Module-Based Breeding of High Yield and Abiotic Resistant Plants in Universities of Shandong, College of Agriculture, Ludong University, Yantai, Shandong 264025, China; State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A & F University, Yangling, Shaanxi 712100, China;Key Laboratory of fruit tree research in Ganzi Academy of Agricultural Sciences, Kangding, Sichuan 626000, China;State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A & F University, Yangling, Shaanxi 712100, China;State Key Laboratory of Crop Stress Biology for Arid Areas/Shaanxi Key Laboratory of Apple, College of Horticulture, Northwest A & F University, Yangling, Shaanxi 712100, Chin

Malus × domestica;MdFRK2;Drought stress;Sugar;Auxin;Signal transductio

Soluble sugars function not only as the energy and structural blocks supporting plants, but also as osmoregulators and signal molecules during plant adaptation to water deficit. Here, we investigated drought resistance in transgenic apple (Malus × domestica) overexpressing MdFRK2, a key gene regulating fructose content and sugar metabolism. There is no obvious phenotypic difference between MdFRK2-overexpressing transgenic plants and WT plants under the well-watered condition. However, the transgenic plants and the grafted plants using MdFRK2-overexpressing rootstock exhibited improved tolerance to drought stress. Overexpression of MdFRK2 significantly promoted the growth of root system under drought stress. RNA sequencing showed that under drought stress, genes involved in sugar metabolism, transcription regulation, signal transduction or hormone metabolism were differentially expressed in MdFRK2 transgenic plants. Consistent with the gene expression profile, the activities of enzyme (SDH, FRK and NI) involved in sugar metabolism in the roots of MdFRK2 transgenic plants were significantly higher than those of untransformed control plants after drought stress. Under drought stress, overexpression of MdFRK2 promoted the accumulation of IAA, and decreased the contents of ABA and CK in apple root system. In conclusion, these results suggest that MdFRK2 can promote the growth of apple roots under drought stress by regulating sugar metabolism and accumulation, hormone metabolism and signal transduction, and then resist drought stress.