• Root-knot nematodes, Meloidogyne spp., secrete effectors to modulate plant immune responses and establish a parasitic relationship with host plants. However, the functions and plant targets of C-type lectin (CTL)-like effectors of Meloidogyne incognita remain unknown. Here, we characterized a CTL-like effector of M. incognita, MiCTL1a, and identified its target and role in nematode parasitism.
• In situ hybridization demonstrated the expression of MiCTL1 in the subventral glands; and in planta, immunolocalization showed its secretion during M. incognita parasitism. Virus-induced gene silencing of the MiCTL1 reduced the infection ability of M. incognita in Nicotiana benthamiana. The ectopic expression in Arabidopsis not only increased susceptibility to M. incognita but also promoted root growth.
• Yeast two-hybrid and co-immunoprecipitation assays revealed that MiCTL1a interacts with Arabidopsis catalases, which play essential roles in hydrogen peroxide homeostasis. Knockout or overexpression of catalases showed either increased or reduced susceptibility to M. incognita, respectively. Moreover, MiCTL1a not only reduced catalase activity in vitro and in planta but also modulated stress-related gene expressions in Arabidopsis.
• Our data suggest that MiCTL1a interacts with plant catalases and interferes with catalase activity, allowing M. incognita to establish a parasitic relationship with its host by fine-tuning responses mediated by reactive oxygen species.

中文翻译：

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南方根结线虫 C 型凝集素效应物靶向植物过氧化氢酶以促进寄生

• 根结线虫，根结线虫属，分泌效应来调节植物免疫反应，并建立与寄主植物寄生关系。然而，南方根结线虫的 C 型凝集素 (CTL) 样效应物的功能和植物靶点仍然未知。在这里，我们表征了M. incognita的 CTL 样效应子MiCTL1a，并确定了它在线虫寄生中的靶标和作用。
• 原位杂交证实了MiCTL1在腹下腺中的表达；而在足底，免疫定位显示出其在南方根结线虫寄生期间的分泌。病毒诱导的MiCTL1基因沉默降低了M. incognita在本氏烟草中的感染能力。拟南芥中的异位表达不仅增加了对M. incognita的易感性，而且促进了根系的生长。
• 酵母双杂交和免疫共沉淀测定表明，MiCTL1a与拟南芥过氧化氢酶相互作用，在过氧化氢稳态中起重要作用。过氧化氢酶的敲除或过表达分别显示出对M. incognita 的敏感性增加或减少。此外，MiCTL1a 不仅降低了体外和植物体内的过氧化氢酶活性，而且还调节了拟南芥中与应激相关的基因表达。
• 我们的数据表明 MiCTL1a 与植物过氧化氢酶相互作用并干扰过氧化氢酶活性，从而允许M. incognita通过微调活性氧介导的反应与其宿主建立寄生关系。