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Cloning and functional analysis of three genes encoding polygalacturonase-inhibiting proteins from Capsicum annuum and transgenic CaPGIP1 in tobacco in relation to increased resistance to two fungal pathogens

Wang, Xiuju, Zhu, Xiaoping, Tooley, Paul, Zhang, Xiuguo
Plant molecular biology 2013 v.81 no.4-5 pp. 379
Alternaria alternata, Capsicum annuum, Colletotrichum, Nicotiana tabacum, Phytophthora capsici, abscisic acid, cell walls, cold stress, disease resistance, enzyme inhibition, enzyme inhibitors, foliar diseases, fungal diseases of plants, gene expression regulation, genes, glycoproteins, leaves, methyl jasmonate, molecular cloning, peppers, plant damage, plant pathogenic fungi, plant response, polygalacturonase, recombinant proteins, salicylic acid, tobacco, transgenic plants
Polygalacturonase-inhibiting proteins (PGIPs) are plant cell wall glycoproteins that can inhibit fungal endopolygalacturonases (PGs). The PGIPs directly reduce the aggressive potential of PGs. Here, we isolated and functionally characterized three members of the pepper (Capsicum annuum) PGIP gene family. Each was up-regulated at a different time following stimulation of the pepper leaves by Phytophthora capcisi and abiotic stresses including salicylic acid, methyl jasmonate, abscisic acid, wounding and cold treatment. Purified recombinant proteins individually inhibited activity of PGs produced by Alternaria alternata and Colletotrichum nicotianae, respectively, and virus-induced gene silencing in pepper conferred enhanced susceptibility to P. capsici. Because three PGIP genes acted similarily in conferring resistance to infection by P. capsici, and because individually purified proteins showed consistent inhibition against PG activity of both pathogens, CaPGIP1 was selected for manipulating transgenic tobacco. The crude proteins from transgenic tobacco exhibited distinct enhanced resistance to PG activity of both fungi. Moreover, the transgenic tobacco showed effective resistance to infection and a significant reduction in the number of infection sites, number of lesions and average size of lesions in the leaves. All results suggest that CaPGIPs may be involved in plant defense response and play an important role in a plant’s resistance to disease.