Study on the mechanism of chitosan-induced resistance to black shank in tobacco

Chitosan (CTS) can directly inhibit the growth and reproduction of plant pathogenic fungi and bacteria, and induce disease resistance in plants against pathogens, but its intrinsic induction mechanism has not been studied. Tobacco black shank is one of the most destructive diseases in tobacco production.In order to explore the potential mechanism of CTS-induced resistance to P.nicotianae parasiticus, this study pretreated tobacco seedlings with CTS at a concentration of 200 mg/L. The results showed that CTS pretreated tobacco in a 44% reduction in disease incidence and 63.9% reduction in disease index, a significant increase in H2O2, lignin and callose content and SA, JA, and ABA and JA-Ile resistance hormones, and an upregulation of many relevant differentially expressed genes (DEGs) involved in defense responses in CTS pretreated tobacco. Among them, the DEGs in "glutathione metabolism", "MAPK signaling pathway-plant" and "Plant hormone signal transduction" pathways were significantly up-regulated. Based on the results of the experimental physiological indicators and transcriptome, this study proposes and discusses the potential molecular mechanism of chitosan-induced resistance to black shank in tobacco.

壳聚糖（Chitosan, CTS）可直接抑制植物病原真菌与细菌的生长繁殖，并诱导植物对病原菌的抗病性，但其内在诱导机制尚未得到研究。烟草黑胫病是烟草生产中破坏性最强的病害之一。为探究CTS诱导烟草抗P.nicotianae parasiticus的潜在机制，本研究采用浓度为200 mg/L的CTS预处理烟草幼苗。结果显示，经CTS预处理的烟草发病率降低44%，病情指数下降63.9%；其过氧化氢（hydrogen peroxide, H₂O₂）、木质素与胼胝质的含量，以及水杨酸（salicylic acid, SA）、茉莉酸（jasmonic acid, JA）、脱落酸（abscisic acid, ABA）和茉莉酰异亮氨酸（jasmonoyl-isoleucine, JA-Ile）等抗病激素的水平均显著升高；同时，CTS预处理的烟草中大量参与防御反应的差异表达基因（differentially expressed genes, DEGs）表达上调。其中，"谷胱甘肽代谢""MAPK信号通路-植物（MAPK signaling pathway-plant）"以及"植物激素信号转导"通路中的差异表达基因显著上调。基于上述生理指标与转录组学实验结果，本研究提出并探讨了壳聚糖诱导烟草抗黑胫病的潜在分子机制。