Root-knot nematodes (RKNs) are notorious plant pathogens that cause substantial losses in horticultural crops globally. The tomato RKN resistance gene, Mi-1, is currently the sole commercially available source of resistance. However, its effectiveness significantly declines when soil temperatures exceed 28 ℃. Although numerous studies have explored the immune signaling pathways mediated by Mi-1, the specific plant immune responses affected by high temperatures and the key temperature-sensitive genes involved remain poorly understood. In this study, we demonstrated that the Mi-1-mediated hypersensitive response is impaired at 32 ℃. At this temperature, the production of reactive oxygen species (ROS) in roots is reduced, while callose deposition increases. Through comparative transcriptome analysis between 24 ℃ and 32 ℃, we identified significant changes in hormone signaling pathways, immune signaling, and gene alternative splicing. For instance, the jasmonic acid (JA) pathway was upregulated, and the salicylic acid (SA) pathway was inhibited at 32 ℃. High temperatures also disrupted the MAPK cascade and influenced metabolite synthesis. Notably, most genes upregulated at 24 ℃ were downregulated at 32 ℃. Furthermore, virus-induced gene silencing (VIGS) assays verified that interfering with the expression of differentially expressed genes, such as the JA biosynthesis key gene MYB transcription factor AOS3, the abscisic acid (ABA) synthesis regulation gene JA2, and the heat stress transcription factor A-6b, increased the susceptibility of Mi-1 tomatoes to RKNs. These findings offer crucial insights into the temperature sensitivity of Mi-1 resistance and support the development of RKN-resistant tomatoes that can remain effective under high-temperature conditions.

Root-knot nematodes (RKNs) cause severe diseases in peppers annually around the world. In pepper, the Me3 gene provides a heat-stable and broad-spectrum resistance to RKNs. In this study, several simple sequence repeat (SSR) markers and insertion/deletion (InDel) markers were developed to fine map the Me3 gene. Analysis of 2272 individuals (F₂ progenies) revealed that Me3 was located in a 45-kb DNA region between markers SSR784 and SSR339, in which there were three candidate genes. Among them, as a novel nucleotide binding site and leucine rich repeat (NBS-LRR) family gene, the DNA sequence of Capana09g000163 of pepper line 'HDA149' was 6348 bp in length, with a 2802-bp open reading frame encoding 933 amino acids, including NB-ARC and LRR domains. Tobacco transient expression assays demonstrated that expression of Capana09g000163 triggered a hypersensitive response (HR) in Nicotiana benthamiana leaves. Subcellular localization results showed that the Capana09g000163 protein was localized in the cell nucleus. Ectopic expression of Capana09g000163 in Arabidopsis significantly increased resistance against Meloidogyne incognita compared with the wild-type (WT) Arabidopsis. Furthermore, M. incognita was almost unable to develop in transgenic Arabidopsis expressing Capana09g000163. Taken together, we cloned the Me3 gene and verified that it induced resistance against M. incognita with the methods of map-based cloning and transgenic technology, which may be of great significance to pepper breeding for resistance against RKNs.