褪黑素诱导拟南芥抗芸薹根肿菌

Induced resistance to Plasmodiophora brassicae in Arabidopsis by melatonin

芸薹根肿菌是一种土传性致病菌,严重时可导致作物死亡.利用荧光定量PCR的方法研究褪黑素诱导拟南芥对根肿病的抗病效果及分子机制.结果显示：不同的褪黑素诱导浓度对根肿病的诱抗效果不同,其中,10μmol/L的褪黑素溶液为最佳抗菌浓度,抗诱效果达到47.57%.褪黑素处理后的拟南芥根部的发病程度减轻并且根肿菌孢子囊数目减少.荧光定量PCR技术检测发现,褪黑素诱导拟南芥后,茉莉酸（JA）途径中的标记基因PR3、PR4有明显的过量表达,同时水杨酸（SA）途径中的PR1、PR2和PR5的表达量也呈上升趋势,但上调幅度不明显,表明褪黑素诱导拟南芥产生的抗病过程主要是以JA信号途径为主,SA途径起辅助作用.本研究认为褪黑素可有效抑制由芸薹根肿菌引起的根肿病,为褪黑素在植物防治中的作用提供了新认识.

Plasmodiophora brassicae is a soil-borne pathogen that damages cruciferae crops by causing root tissue to become hyperplastic and enlarged, resulting in crop death in severe cases. P. brassicae forms dormant spores that can survive for up to ten years. Its life history is complex, and it cannot be cultured in vitro, making it difficult to investigate the pathogenesis of its infection. In this study, the effects of melatonin on Plasmodiophora brassicae and its molecular mechanism of infection were investigated to provide theoretical support for the prevention and treatment of the disease, and to develop new methods of disease resistance. Different concentrations of melatonin were applied to Arabidopsis thaliana infected with P. brassicae, and the optimum antibacterial concentration was determined. The root tissue of Arabidopsis thaliana under different treatments was observed on paraffin sections. The expression levels of the pathogenesis-related（PR） genes PR1, PR2, PR3, PR4, and PR5 were analyzed using real-time polymerase chain reaction（PCR）. Melatonin at 10 μmol/L showed the best antibacterial effect, with a control efficacy of 47.57%. After melatonin treatment, both the incidence of Arabidopsis thaliana infection and the number of sporangia were reduced. Real-time PCR analysis indicated that melatonin excited the expression of the jasmonic acid-responsive PR3 and PR4 genes markedly, while the expression levels of PR1, PR2, and PR5 in the salicylic acid pathway also increased; however, the increases were not obvious. High expression of JA-responsive PR3 and PR4 genes hinted that the JA-signaling pathway was essential for melatonin-induced resistance in A. thaliana; salicylic acid-signaling might also have a role. The results showed that melatonin could effectively inhibit the root swelling caused by P. brassicae, providing a new understanding of the role of melatonin in plant disease control.