Purpose Through temporal transcriptomic analysis, this study aims to systematically elucidate the dynamic transcriptional regulatory network in the potato variety ‘Eshu No. 3’, which is susceptible to Alternaria solani infection, and to identify the molecular response characteristics and potential disease resistance target genes during the critical stages of lesion expansion, thereby providing a theoretical basis for the identification of disease resistance genes and the optimization of breeding program.
Methods Potato leaves were infected using the wounding inoculation method, and samples were collected 24, 30 and 36 hours post-inoculation for transcriptomic sequencing. Through differential gene expression analysis, principal component analysis, GO enrichment analysis, KEGG enrichment analysis and transcription factor family classification, the molecular response mechanisms of the host at different stages of pathogen infection were elucidated, and potential disease resistance target genes were identified.
Results Spot diameter increased significantly 36 hours after inoculation with the pathogen, and transcriptomic analysis revealed that the number of differentially expressed genes (DEGs) increased with the duration of infection. Cluster analysis of DEGs showed that the α-linolenic acid metabolism pathway peaked at the 30th hour post-infection, whilst the tricarboxylic acid cycle and glutathione metabolism pathways remained at low levels throughout the infection period, and photosynthesis-related genes were consistently down-regulated. In the GO enrichment analysis, both the catalytic activity pathway and the oxidoreductase activity pathway showed up-regulated expression as the duration of infection increased; in the KEGG enrichment analysis, both the plant-pathogen interaction pathway and the glutathione metabolism pathway were up-regulated as the duration of infection increased. As the duration of pathogen infection increased, the WRKY transcription factor family and the ethylene responsive factor (ERF) family responded rapidly at the 24th hour mark of pathogen infection, and the ERF transcription factor family and the NAC transcription factor family exhibited the highest number of up-regulated genes at the 36th hour post-infection, marking the peak of the plant defence response; at the 36th hour of pathogen infection, the NAC transcription factor family drove programmed cell death. Peroxidase genes were key time-point target genes, their fragments per kilobase of exon model per million mapped fragments (FPKM) remained at high levels throughout the infection process, and their expression levels increased as the duration of infection increased.
Conclusion The defense response of susceptible potato exhibits a temporal pattern characterized by “early signal activation, mid-stage defense intensification, and late-stage programmed cell death”. The 30th hour of pathogen infection represents a critical juncture in the defense-metabolism balance, with increased photosynthetic inhibition driving the reallocation of resources towards defense. The WRKY, ERF and NAC transcription factor families regulate the disease resistance process in a phased manner. At the 30th hour post-infection, the expression levels of the screened peroxidase genes increase, which may inhibit spot expansion.
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