Pectin-Degrading Enzymes during Soursop (Annona muricata L.) Fruit Ripening: A Bioinformatics Approach

The rapid ripening of soursop (Annona muricata L.) fruits is owing to its high respiration rate. Several enzymes affect the fruit cell wall in this process, resulting in the depolymerization of pectin primarily in the homogalacturonan. The main group of enzymes affecting the pectin content of soursop fruits include polygalacturonase (PG), pectate lyase (PL), pectin methylesterase (PME), and PME inhibitors (PMEis). In this study, pectin-degrading enzymes were analyzed using bioinformatic tools to uncover the gaps in our knowledge of this fruit. In this context, 67 genes encoding PG, 33 PL, 58 PME, and 39 PMEi isoenzymes were found. These genes were categorized into several families based on the results of phylogenetic analysis. Regarding the analysis of gene expression, a total of 25 were identified as differentially expressed genes (DEGs) in PG, while 3, 21, and 15 were found for PL, PME, and PMEis, respectively. Likewise, functional enrichment analysis demonstrated that the DEGs are involved in the modification of the cell wall, specifically in the degradation of pectin. On the other hand, gene co-expression networks revealed that the genes PG32 and PG35 affect the expression of PGs, as well as PL19 of the PL family, PME20, PME32, and PME35 of the PME family, and PMEi04 of the PMEi family. This suggests that they have a significant impact on the softening of soursop fruits.