Submitted to: Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/1/2013
Publication Date: 1/19/2013
Publication URL: http://handle.nal.usda.gov/10113/57205
Citation: Wang, X., Zhu, X., Tooley, P.W., Zhang, X. 2013. Molecular cloning and functional analysis of three genes encoding polygalacturonase-inhibiting proteins from Capsicum annuum, and their relation to increased resistance to two fungal pathogens. Plant Physiology. 81:379-400. Interpretive Summary: We studied members of a gene family in pepper that can reduce the pathogenic potential of certain fungi that attack pepper. We characterized the regulation of the genes and showed that their activity increased when pepper leaves were inoculated with the plant pathogen Phytophthora capsici and in response to other stimuli including wounding and cold treatment. Proteins resulting from the activity of these genes showed resistance to the activity of enzymes in specific fungal pathogens. Results of these studies indicate that the genes we characterized may be strongly involved in the defense response of pepper to various pathogens.
Technical Abstract: Polygalacturonase-inhibiting proteins (PGIPs) are plant cell wall glycoproteins that can inhibit fungal endopolygalacturonases (PGs). Inhibiting by PGIPs directly reduces potential PG activity in specific plant pathogenic fungi, reducing their aggressiveness. Here, we isolated and functionally characterized three members of the pepper (Capsicum annuum L.) PGIP gene family. They showed up-regulation expression at different times following inoculation of pepper leaves by Phytophthora capcisi or in response to stresses including salicylic acid (SA), methyl jasmonate (MJA), abscisic acid (ABA), wounding, and cold treatment. Purified recombinant proteins inhibited PG activity from Alternara alternata and Colletotrichum nicotianae respectively, and virus-induced gene silencing in pepper conferred enhanced susceptibility to P. capsici. Three members exhibited similarity in resistance to P. capsici infection and individual purified proteins showed consistent inhibition against PG activity of both fungi. Transgenic tobacco plants also showed effective inhibition of both fungal infection and a significant reduction in the number of infection sites, the number of lesions and the average lesion area in leaves. These results suggest that CaPGIPs may be involved in the plant defense response and play an important role in plant resistance.