During biotic stress, plants use several mechanisms to protect themselves that include the production of reactive oxygen species (ROS), induction of pathogenesis-related proteins and cell death. Some plant growth promoting rhizobacteria (PGPR) are known to act as bio-control agents that protect crops against pathogens. The biocontrol activity of PGPR Paenibacillus lentimorbus (B-30488) against Sclerotium rolfsii showed previously where several defense-related genes were upregulated with ROS induction in tomato. We further evaluate the other possibility, i.e. role of autophagy in enhancing defense in tomato using PGPR. Confocal microscopy revealed the presence of an acidotropic dye Mono Dansyl Cadaverine (MDC) stained autophagosomes in B-30488 treated healthy and infected plants. These autophagosomes almost disappeared in plants treated with an autophagy inhibitor chloroquine. The results were also confirmed by ultrastructural analysis of leaf tissues using transmission electron microscopy. Enhanced expression of autophagy-related genes was also monitored in B-30488 primed fungal infected tissues as compared to control by qRT-PCR. Results of ROS accumulation, fluorescence, confocal and transmission electron microscopy and gene expression analysis revealed induction of autophagy using B-30488 as a biocontrol agent suggesting a role in enhancing disease resistance in tomato. Overall, the present study indicated a role of B-30488 as a biocontrol in enhancing disease resistance in tomato and also assists a better understanding of fungal pathogenesis that is expected to be useful in developing new strategies for disease control.

在生物胁迫期间，植物使用多种保护自身的机制，包括产生活性氧（ROS），诱导与病程相关的蛋白质和细胞死亡。已知某些植物促生根瘤菌（PGPR）可以作为生物防治剂来保护农作物免受病原体侵害。PGPR的生物防治活性类芽孢杆菌缓死（B-30488）抗白绢病以前的研究表明，番茄中的ROS诱导上调了几个与防御相关的基因。我们进一步评估了另一种可能性，即自噬在使用PGPR增强番茄防御中的作用。共聚焦显微镜显示在B-30488处理的健康和感染植物中存在着一种向酸性染料Mono Dansyl Cadaverine（MDC）染色的自噬体。这些自噬体在用自噬抑制剂氯喹处理过的植物中几乎消失了。使用透射电子显微镜对叶片组织进行超微结构分析也证实了该结果。与通过qRT-PCR进行的对照相比，在B-30488引发真菌感染的组织中还监测了自噬相关基因的增强表达。ROS积累，荧光，共聚焦和透射电子显微镜及基因表达分析表明，使用B-30488作为生物防治剂可诱导自噬，提示其在增强番茄抗病性中的作用。总体而言，本研究表明B-30488作为生物防治在增强番茄抗病性中的作用，也有助于更好地了解真菌的发病机理，预计该真菌可用于开发新的疾病控制策略。