<i>JrGA20ox1</i>-transformed rootstocks deliver drought response signals to wild-type scions in grafted walnut
Heqiang Lou, Fengmin Wang, Jiaqi Zhang, Guangli Wei, Jingjing Wei, Hengkang Hu, Yan Li, Ketao Wang, Zhengjia Wang, Youjun Huang, Jiasheng Wu, Pei Dong, Jianqin Huang, Qixiang Zhang
Abstract
Abstract Targeted regulation using transgrafting technology has become a trend. However, the mechanisms of transgene-derived signal communication between rootstocks and scions remain unclear in woody plants. Here, we grafted wild-type (WT) walnut (Juglans regia L.) on WT (WT/WT), JrGA20ox1 (encodes a gibberellin 20-oxidase)-overexpressing (WT/OE), and JrGA20ox1-RNAi transformation (WT/RNAi) walnut in vitro. We aimed to elucidate the mechanisms of JrGA20ox1-derived signal communication under PEG-simulated drought stress between rootstocks and scions in walnut. We demonstrated that JrGA20ox1-OE and JrGA20ox1-RNAi rootstocks could transport active gibberellins (GAs) and JrGA20ox1-RNAi vector-produced sRNAs to WT scions under PEG-simulated drought stress, respectively. The movement of sRNAs further led to a successive decline in JrGA20ox1 expression and active GA content. Meanwhile, unknown mobile signals may move between rootstocks and scions. These mobile signals reduced the expression of a series of GA-responsive and GA-non-responsive genes, and induced ROS production in guard cells and an increase in ABA content, which may contribute to the drought tolerance of WT/RNAi, while the opposite occurred in WT/OE. The findings suggest that JrGA20ox1-derived rootstock-to-scion movement of signals is involved in drought tolerance of scions. Our research will provide a feasible approach for studying signal communication in woody plants.