Abstract
Modification of cell wall polysaccharide in the plant plays an important role in response to fungi infection. However, the mechanism of fungi infection on cell wall modification need further clarification. In this study, the effects of Penicillium italicum inoculation on ‘shatangju’ mandarin disease development and the potential mechanism of cell wall polysaccharides modification caused by P. italicum were investigated. Compared to the control fruit, P. italicum infection modified the cell wall polysaccharides, indicated by water-soluble pectin (WSP), acid-soluble pectin (ASP), hemicellulose and lignin contents change. P. italicum infection enhanced the activities of polygalacturonase (PG), pectin methylesterase (PME), and the expression levels of xyloglucanendotransglucosylase/hydrolase (XTH) and expansin, which might contribute to cell wall disassembly and cellular integrity damage. Additionally, higher accumulation of reactive oxygen species (ROS) via decreasing antioxidant metabolites and the activities of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) also contributed to the cell wall polysaccharides modification. Meanwhile, the gene expression levels of hydroxyproline-rich glycoprotein (HRGP) and germin-like protein (GLP) were inhibited by pathogen infection. Altogether, these findings suggested that cell wall degradation/modification caused by non-enzymatic and enzymatic factors was an important strategy for P. italicum to infect ‘shatangju’ mandarin.
Highlights
Citrus is an important fruit and widely grown worldwide
To acquire more information on the infection mechanism of P. italicum on citrus fruit, we focused on the effects of pathogen infection on cell wall modification through enzymatic and non-enzymatic aspects
This study aims to clarify the mechanism of P. italicum infection inducing disease development of stored ‘shatangju’ mandarin fruit in a perspective of cell wall metabolism
Summary
Citrus is an important fruit and widely grown worldwide. 25% of citrus fruits are lost due to postharvest decay caused by fungal infections [2,3]. Penicillium digitatum and Penicillium italicum are the most important pathogens responsible for significant postharvest losses in citrus fruit [4,5]. P. italicum, as one of the most important fungal pathogens, triggers blue mold diseases, and causes decay of citrus fruit worldwide [2,6]. Though the optimum temperature for germination and growth of P. italicum is 25 ◦ C, it can be active at 4–30 ◦ C or even at 0 ◦ C; but no growth at 37 ◦ C [5]. Fungicides are widely used to control postharvest fungal disease. The use of fungicides caused public concern over human
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