CsIVP functions in vasculature development and downy mildew resistance in cucumber
Shuangshuang Yan, Kang Ning, Zhongyi Wang, Xiaofeng Liu, Yanting Zhong, Lian Ding, Hailing Zi, Zhihua Cheng, Xuexian Li, Hongyan Shan, Qingyang Lv, Laixin Luo, Renyi Liu, Liying Yan, Zhaoyang Zhou, William J. Lucas, Xiaolan Zhang
Abstract
Domesticated crops with high yield and quality are frequently susceptible to pathogen attack, whereas enhancement of disease resistance generally compromises crop yield. The underlying mechanisms of how plant development and disease resistance are coordinately programed remain elusive. Here, we showed that the basic Helix-Loop-Helix (bHLH) transcription factor Cucumis sativus Irregular Vasculature Patterning (CsIVP) was highly expressed in cucumber vascular tissues. Knockdown of CsIVP caused severe vasculature disorganization and abnormal organ morphogenesis. CsIVP directly binds to vascular-related regulators YABBY5 (CsYAB5), BREVIPEDICELLUS (CsBP), and AUXIN/INDOLEACETIC ACIDS4 (CsAUX4) and promotes their expression. Knockdown of CsYAB5 resulted in similar phenotypes as CsIVP-RNA interference (RNAi) plants, including disturbed vascular configuration and abnormal organ morphology. Meanwhile, CsIVP-RNAi plants were more resistant to downy mildew and accumulated more salicylic acid (SA). CsIVP physically interacts with NIM1-INTERACTING1 (CsNIMIN1), a negative regulator in the SA signaling pathway. Thus, CsIVP is a novel vasculature regulator functioning in CsYAB5-mediated organ morphogenesis and SA-mediated downy mildew resistance in cucumber.