Negi Sanjana, Tak Himanshu, Bhakta Subham, Tiwari Mahesh, Ganapathi Thumballi Ramabhatta, Singh Sudhir, Ballal Anand
National Agri-Food Biotechnology Institute, Department of Biotechnology, Mohali, India.
Nuclear Agriculture and Biotechnology Division, Bhabha Atomic Research Centre, Mumbai, India.
Plant Biotechnol J. 2025 Aug;23(8):3283-3299. doi: 10.1111/pbi.70131. Epub 2025 May 26.
Constitutive expression of hypersensitive cell-death-inducing effectors secreted by pathogens has proved to be difficult in plants. Herein, xylem-specific promoters (P or P) were utilized to express three cell-death-inducing proteins (FocSIX1A, FocSIX6 or TvSm1) of fungal origin in banana plants. The regenerated plants were not only healthy but also showed improved resistance to fungal (Foc vcg0124 and Foc vcg0125) infection. These banana plants developed systemic resistance-like symptoms, including elevated jasmonic acid content, callose depositions, increased xylem wall thickness and expression of several defence-associated genes. Interestingly, expression of NAC105, a homologue of VND (vascular-related NAC domain) transcription factor, was elevated in all these transgenic lines. Employing a novel positive-feedback loop using VND genes, banana lines with thicker xylem walls devoid of any ectopic lignification were developed. Enhanced disease resistance of these lines against Foc strains, increased expression of defence genes, elevated jasmonic acid content and quantitative elevation of phenolic compounds provide evidence that elevation in xylem wall thickness does indeed contribute to systemic resistance by playing a crucial role in regulating immune responses. The current study demonstrates that (a) plants that express cell-death-inducing proteins in xylem can be regenerated, (b) these plants are healthy and show enhanced disease resistance and (c) a novel feedback loop involving vascular proteins, which specifically elevates xylem wall thickness without negatively affecting growth, exists in plants.
事实证明，在植物中组成型表达病原体分泌的诱导过敏细胞死亡效应子是困难的。在此，利用木质部特异性启动子（P或P）在香蕉植株中表达三种真菌来源的诱导细胞死亡蛋白（FocSIX1A、FocSIX6或TvSm1）。再生植株不仅健康，而且对真菌（Foc vcg0124和Foc vcg0125）感染表现出更强的抗性。这些香蕉植株出现了类似系统抗性的症状，包括茉莉酸含量升高、胼胝质沉积、木质部细胞壁厚度增加以及几个防御相关基因的表达。有趣的是，VND（血管相关NAC结构域）转录因子的同源物NAC105在所有这些转基因株系中的表达都有所升高。利用VND基因构建了一个新的正反馈回路，培育出了木质部细胞壁更厚且无任何异位木质化的香蕉株系。这些株系对Foc菌株的抗病性增强、防御基因表达增加、茉莉酸含量升高以及酚类化合物的定量增加，这些证据表明木质部细胞壁厚度的增加确实通过在调节免疫反应中发挥关键作用而有助于系统抗性。目前的研究表明：（a）可以再生在木质部中表达诱导细胞死亡蛋白的植物；（b）这些植物健康且抗病性增强；（c）植物中存在一种涉及血管蛋白的新反馈回路，该回路能特异性增加木质部细胞壁厚度而不负面影响生长。
