Liu Cheng-Qian, Hu Kang-Di, Li Ting-Ting, Yang Ying, Yang Feng, Li Yan-Hong, Liu He-Ping, Chen Xiao-Yan, Zhang Hua
School of Food Science and Engineering, Hefei University of Technology, Hefei, China.
College of Environment and Energy Engineering, Anhui Jianzhu University, Hefei, China.
PLoS One. 2017 Mar 3;12(3):e0173277. doi: 10.1371/journal.pone.0173277. eCollection 2017.
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.
黑曲霉是一种腐生真菌，广泛分布于土壤、空气和谷物中，可导致水果采后病害。多聚半乳糖醛酸酶（PG）是真菌病原体中降解植物细胞壁的主要酶之一。为了评估外切多聚半乳糖醛酸酶基因pgxB的缺失是否会影响真菌对水果的致病性，通过同源重组在黑曲霉MA 70.15（野生型）中缺失了pgxB基因。与野生型相比，ΔpgxB突变体表现出相似的生长行为。与马铃薯葡萄糖琼脂培养基相比，果胶培养基诱导野生型和ΔpgxB中所有果胶酶基因的表达均显著升高。然而，ΔpgxB突变体对苹果果实的毒性较低，因为ΔpgxB突变体引起的坏死直径明显小于野生型。定量PCR结果表明，在苹果果实感染过程中，与野生型相比，ΔpgxB突变体中多聚半乳糖醛酸酶基因pgaI、pgaII、pgaA、pgaC、pgaD和pgaE的基因表达增强。这些结果证明，尽管ΔpgxB突变体中其他多聚半乳糖醛酸酶基因的表达增加，但pgxB基因的缺失显著降低了黑曲霉对苹果果实的毒性，表明pgxB在苹果果实的感染过程中起重要作用。
