Abstract：
Trichoderma spp. can enhance plant resistance against a wide range of biotic stressors. However, the fundamental mechanisms by which Trichoderma enhances plant resistance against Meloidogyne incognita, known as root-knot nematodes (RKNs), are still unclear. Here, we identified a strain of Trichoderma asperellum (T141) that could effectively suppress RKN infestation in tomato (Solanum lycopersicum L.). Nematode infestation led to an increase in the concentrations of reactive oxygen species (ROS) and malondialdehyde (MDA) in roots but pre-inoculation with T141 significantly decreased oxidative stress. The reduction in ROS and MDA was accompanied by an increase in the activity of antioxidant enzymes and the accumulation of flavonoids and phenols. Moreover, split root test-based analysis showed that T141 inoculation in local roots before RKN inoculation increased the concentration of phytohormone jasmonate (JA) and the transcripts of JA synthesis and signaling-related genes in distant roots. UPLC-MS/MS-based metabolomics analysis identified 1051 differentially accumulated metabolites (DAMs) across 4 pairwise comparisons in root division test, including 81 flavonoids. Notably, 180 DAMs were found in comparison between RKN and T141-RKN, whereas KEGG annotation and enrichment analysis showed that the secondary metabolic pathways, especially the flavonoid biosynthesis, played a key role in the T141-induced systemic resistance to RKNs. The role of up-regulated flavonoids in RKN mortality was further verified by in vitro experiments with the exogenous treatment of kaempferol, hesperidin and rutin on J2-stage RKNs. Our results revealed a critical mechanism by which T141 induced resistance of tomato plants against the RKNs by systemically promoting secondary metabolism in distant roots.
摘要：
木霉属。可以增强植物对各种生物胁迫的抵抗力。然而,木霉增强植物对南方根结线虫抗性的基本机制，被称为根结线虫（RKN），还不清楚。这里,我们确定了一种可以有效抑制番茄（SolanumlycopersicumL.）中RKN侵染的木霉菌（T141）菌株。线虫的侵染导致根中活性氧（ROS）和丙二醛（MDA）的浓度增加，但预接种T141可显着降低氧化应激。ROS和MDA的减少伴随着抗氧化酶活性的增加以及类黄酮和酚类物质的积累。此外，基于裂根试验的分析表明，在RKN接种之前，在局部根部接种T141会增加植物激素茉莉酸（JA）的浓度以及远处根部JA合成和信号相关基因的转录本。基于UPLC-MS/MS的代谢组学分析在根划分试验中通过4对比较确定了1051种差异积累的代谢物（DAM），包括81种类黄酮。值得注意的是,在RKN和T141-RKN之间的比较中发现了180个DAM，而KEGG注释和富集分析表明，次级代谢途径，尤其是类黄酮的生物合成，在T141诱导的系统对RKN的抵抗中起关键作用。通过山奈酚的外源处理的体外实验进一步验证了上调的黄酮类化合物在RKN死亡率中的作用，橙皮苷和芦丁在J2期RKN上。我们的结果表明，T141通过系统地促进远根的次生代谢来诱导番茄植株对RKN的抗性的关键机制。
