Transcriptome analysis of response of Passiflora edulis by Alternaria alternate infection, the pathogen of scab disease postprint

Abstract: To elucidate the transcriptional dynamics of Passiflora edulis in response to infection by Alternaria alternata, the causal agent of scab disease, this study employed transcriptome sequencing to compare gene expression profiles at 1 to 5 days post-inoculation (dpi). The primary objective was to characterize the temporal transcriptional reprogramming of P. edulis during distinct phases of pathogen challenge. The key findings were as follows: (1) The most pronounced transcriptional alterations occurred at 1 dpi and 4 dpi, with 3042 and 1117 differentially expressed genes (DEGs) identified, respectively. In stark contrast, only 6 DEGs were detected at 5 dpi. (2) Following co-expression network analysis and core gene mining, it was found that trehalose-6-phosphate synthase and expansin showed significant downregulation after inoculation, whereas omega-6 fatty acid desaturase and corticosteroid 11-beta-dehydrogenase exhibited a trend of first decreasing and then increasing after inoculation with the pathogen, opposite to the trend observed in non-inoculated passion fruit, which increased first and then decreased. (3) Further analysis of the expression trend of fatty acid desaturase revealed that at 1 dpi and 4 dpi after inoculation, the expression levels of genes related to omega-6 fatty acid desaturase were upregulated to varying degrees, and genes related to cytochrome b5 associated with fatty acid desaturase also showed significant upregulation during the early stage of inoculation. (4) Analysis of WRKY transcription factors showed that the highest number of WRKY-related genes were upregulated at 1 dpi and 4 dpi, while no significant changes were observed at 3 dpi and 5 dpi. In conclusion, the most intense response of Passiflora edulis to Alternaria alternata infection occurred at 1 dpi and 4 dpi. In the first phase, non-biotic stress-related mechanisms were primarily involved in defense against the pathogen, whereas in the second phase, biotic stress-related mechanisms played a dominant role. This study provides important insights into the mechanism of passion fruit response to Alternaria alternata infection and has practical implications for field fungicide control of scab disease, helping to reduce disease impact on fruit quality.