Expression analysis of the NEP-1 and cell-wall degrading genes of Gilbertella persicaria during pathogenesis in papaya (Carica papaya L.) fruits

Abstract Gilbertella persicaria is a plant pathogenic fungus that develops a necrotrophic lifestyle during its infection process in papaya fruits. The maceration of fruit tissues is observed from 12 h post-inoculation (hpi) and is related to the activity of the hydrolytic enzymes that allow the cell wall degrading and favour the diseases development at approximately 48 hpi. In mucorales fungi including G. persicaria, the information about their enzymatic capacity is scarce, and therefore, the objective of this research was to evaluate the gene expression of G. persicaria during pathogenesis in papaya fruits and the information obtained was related to the degradability capacity of the fungus on different substrates through the analysis of in vitro enzymatic activity. For this, an in silico analysis of the genome of the CBS 190.32 strain of G. persicaria was performed, and oligonucleotides were designed. Furthermore, the expression of pathogenicity genes coding for the enzymes endoglucanase V (Egl V), β-glucosidases (Bgl) I and II, xyloglucanase (Xln), endopolygalacturonase (Epg), pectin methylesterase (Pme), aspartic protease (Asp), peptidases of the types trypsin (Try) and subtilase (Sub), and the necrosis- and ethylene-inducing peptide (Nep1) was evaluated via real-time quantitative PCR. As a result, during the early stages of infection (germination and penetration), the genes Nep1, Egl V, Epg and Asp were expressed in vivo, showing maximum expression between 24 and 30 hpi (maceration and colonization of tissues) with 26.53, 357.05, 215.26 and 162.01 times, respectively. We can conclude that the enzymatic capacity of G. persicaria allows it to carry out a rapid invasion of fruit tissues. This information improves our understanding of the infection process in fungi with a necrotrophic lifestyle.