Abstract
There are several phytosanitary problems that have been causing serious damage to the Capsicum crops, including anthracnose. Upon attack by certain pathogens, various protein molecules are produced, which are known as proteins related to pathogenesis (PR proteins), including antimicrobial peptides such as protease inhibitors, defensins and lipid transfer proteins (LTPs). The objective of this work is to identify antimicrobial proteins and/or peptides of two genotypes from Capsicum annuum fruits infected with Colletotrichum gloeosporioides. The fungus was inoculated into Capsicum fruits by the deposition of a spore suspension (106 conidia ml−1), and after 24 and 48 h intervals, the fruits were removed from the humid chamber and subjected to a protein extraction process. Protein analysis of the extracts was performed by tricine gel electrophoresis and Western blotting. The distinctive bands between genotypes in the electrophoresis profiles were subjected to mass spectrometry sequencing. Trypsin inhibition assays, reverse zymographic detection of protease inhibition and β-1,3-glucanase activity assays were also performed and extracts were also tested for their ability to inhibit the growth of C. gloeosporioides fungi ‘in vitro’. There were several low molecular weight proteins in all treated samples, and some treatments in which antimicrobial peptides such as defensin, lipid transfer protein (LTP) and protease inhibitor have been identified. It was shown that the green fruits are more responsive to infection, showing the production of antimicrobial peptides in response to injury and inoculation of the fungus, what did not occur in ripe fruits under any treatment.
Highlights
Sweet and chili peppers belong to the Solanaceae family and to the Capsicum genus, which encompasses more than 31 described species, with only five being domesticated (Capsicum annuum var. annuum, C. baccatum var. pendulum and umbilicatum, C. chinense, C. frutescens and C. pubescens) [1]
The fungus C. gloeosporioides is the main responsible for anthracnose in fruits of Capsicum in Brazil, and can appear in any part of the plant, from its development in the field to even in fruits stored in the post-harvest phase [26]
The pattern of the low molecular weight proteins of the ripe and immature fruits of C. annuum inoculated with C. gloeosporioides, at 24 and 48 h after inoculation, was analyzed by tricine gel electrophoresis (Figure 1)
Summary
Sweet and chili peppers belong to the Solanaceae family and to the Capsicum genus, which encompasses more than 31 described species, with only five being domesticated (Capsicum annuum var. annuum, C. baccatum var. pendulum and umbilicatum, C. chinense, C. frutescens and C. pubescens) [1]. During the cultivation of Capsicum, the plants may be vulnerable to several pests and diseases, what may lead to severe losses for farmers. Anthracnose is a disease of complex etiology, caused by distinct isolates of different species of Colletotrichum [2]. It is one of the most destructive diseases of sweet and chili peppers in tropical and subtropical regions, and its spread occurs mainly in crops that are grown outdoors during periods of high. The fungus produces conidia (spores) as reproductive structures, which are released and disseminated by splashes of rain, wind, and insects, among other vectors [3]
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