A gamma‐thionin protein from apple, MdD1, is required for defence against S ‐RNase‐induced inhibition of pollen tube prior to self/non‐self recognition

作者：Zhaoyu Gu, Wei Li, James Doughty, Dong Meng, Qing Yang, Hui Yuan, Yang Li, Qiuju Chen, Jie Yu, Chun sheng Liu, Tianzhong Li · 发表于：Plant Biotechnology Journal · 年份：2019 · DOI：10.1111/pbi.13131 · 被引用次数：27 · 研究领域：Plant Reproductive Biology、Plant and animal studies、Insect-Plant Interactions and Control

Apple exhibits S-RNase-mediated self-incompatibility. Although the cytotoxic effect of S-RNase inside the self-pollen tube has been studied extensively, the underlying defence mechanism in pollen tube in Rosaceae remains unclear. On exposure to stylar S-RNase, plant defence responses are activated in the pollen tube; however, how these are regulated is currently poorly understood. Here, we show that entry of both self and non-self S-RNase into pollen tubes of apple (Malus domestica) stimulates jasmonic acid (JA) production, in turn inducing the accumulation of MdMYC2 transcripts, a transcription factor in the JA signalling pathway widely considered to be involved in plant defence processes. MdMYC2 acts as a positive regulator in the pollen tube activating expression of MdD1, a gene encoding a defence protein. Importantly, MdD1 was shown to bind to the RNase activity sites of S-RNase leading to inhibition of enzymatic activity. This work provides intriguing insights into an ancient defence mechanism present in apple pollen tubes where MdD1 likely acts as a primary line of defence to inhibit S-RNase cytotoxicity prior to self/non-self recognition.