Transcriptome and cell wall degrading enzyme-related gene analysis of Pestalotiopsis neglecta in response to sodium pheophorbide a

Sodium pheophorbide a (SPA) is a new alternative fungicide with low toxicity and high efficiency, which has high fungicidal activity against Pestalotiopsis neglecta, a pathogen that causes black spot needle blight of Pinus sylvestris var. mongolica. To utilize SPA for plant disease control, understanding its antifungal mechanism is essential. Six cDNA libraries were constructed from 3 d-old P. neglecta mycelia (three SPA-infected and three untreated groups) and 29,850 expressed genes were obtained by Illumina HiSeq4000 sequencing. Compared with controls, 3268 differentially expressed genes (DEGs) were identified in SPA-treated groups, including 1879 upregulated and 1389 downregulated genes. Most DEGs were involved in the metabolism of amino acids, carbohydrates, and lipids, as well as cell structure and genetic information processing. These findings were further confirmed by decreased conductivity, RNA and protein content, and activities of nicotinamide adenine dinucleotide-dependent malate dehydrogenase, citrate synthase, isocitrate dehydrogenase, and succinate dehydrogenase. Moreover, qRT-PCR verified the reliability of the transcriptome results. After treatment with SPA at different concentrations for 60 min, the expressions of three cell wall degrading enzyme-related genes (PnEG, PnBG, and PnPG) were all suppressed. Overall, this study provided insights into the molecular mechanisms through which SPA inhibits P. neglecta, increasing the possibility of developing SPA into an effective fungicide in the future.

Keywords: Antifungal mechanism; Differentially expressed genes; Pestalotiopsis neglecta; Sodium pheophorbide a; Transcriptome.