Abstract
Aspergillus niger, a saprophytic fungus, is widely distributed in soil, air and cereals, and can cause postharvest diseases in fruit. Polygalacturonase (PG) is one of the main enzymes in fungal pathogens to degrade plant cell wall. To evaluate whether the deletion of an exo-polygalacturonase gene pgxB would influence fungal pathogenicity to fruit, pgxB gene was deleted in Aspergillus niger MA 70.15 (wild type) via homologous recombination. The ΔpgxB mutant showed similar growth behavior compared with the wild type. Pectin medium induced significant higher expression of all pectinase genes in both wild type and ΔpgxB in comparison to potato dextrose agar medium. However, the ΔpgxB mutant was less virulent on apple fruits as the necrosis diameter caused by ΔpgxB mutant was significantly smaller than that of wild type. Results of quantitive-PCR showed that, in the process of infection in apple fruit, gene expressions of polygalacturonase genes pgaI, pgaII, pgaA, pgaC, pgaD and pgaE were enhanced in ΔpgxB mutant in comparison to wild type. These results prove that, despite the increased gene expression of other polygalacturonase genes in ΔpgxB mutant, the lack of pgxB gene significantly reduced the virulence of A. niger on apple fruit, suggesting that pgxB plays an important role in the infection process on the apple fruit.
Highlights
Pectinases are the most important pathogenic factor in plant pathogenic bacteria and fungi [1,2,3,4]
We described the construction of a mutant disrupted in the pgxB gene in A. niger
ΔpgxB exhibited no growth rate reduction on potato dextrose agar medium (PDA) and pectin medium compared with wild type, which means the disruption of pgxB did not weaken its ability of decomposing pectin as carbon source (Fig 2)
Summary
Pectinases are the most important pathogenic factor in plant pathogenic bacteria and fungi [1,2,3,4]. They are responsible for pathogens to decompose pectin in plant cell wall. Pectinases are consisted of polygalacturonase (PG), pectin lyase (PNL), pectate lyase (PL), pectinesterase (PE), pectin methyl esterase (PME). Polygalacturonase is one of the major members of pectinases which cleaves α-1,4-glycosidic of D-galacturonic acid in pectin and it is classified into endo- and exopolygalacturonase on the basis of the way of eliminating galacturonic acid [6,7].
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
