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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Molecular Plant Pathology Laboratory » Research » Publications at this Location » Publication #326465

Title: Wound induced Beta vulgaris polygalacturonase-inhibiting protein genes encode a longer leucine-rich repeat domain and inhibit fungal polygalacturonases

item Li, Haiyan
item Smigocki, Anna

Submitted to: Physiological and Molecular Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/9/2016
Publication Date: 6/16/2016
Citation: Li, H., Smigocki, A.C. 2016. Wound induced Beta vulgaris polygalacturonase-inhibiting protein genes encode a longer leucine-rich repeat domain and inhibit fungal polygalacturonases. Physiological and Molecular Plant Pathology. doi:10.1016/j.pmpp.2016.06.004.

Interpretive Summary: Plants are under constant threat of infections caused by several pathogens, including viruses, bacteria, fungi, nematodes and insects. As a consequence, plants have evolved a number of strategies for self-protection. One of these mechanisms involves the production of antimicrobial compounds. Polygalacturonase-inhibiting proteins (PGIPs) are one of these compounds that are produced in plants to inhibit polygalacturonases, the enzymes released by pathogens and insect pests to break down cell walls during attack. To better understand how plants protect themselves from disease and insect pests, we isolated three sugar beet PGIP components from two breeding lines. The sugar beet PGIPs shared the typical structure of other PGIPs but contained a longer stretch of repeating amino acids that was responsible for disease response. We demonstrated that the sugar beet PGIP components were involved in insect feeding and fungal infection. We propose that sugar beet PGIPs play an active role in defense responses. This information will be of interest to the scientists as well as to the breeders and sugar producers to develop improved crops capable of resisting pests and diseases thus improving the safety of consumable foods by reducing the usage of pesticides.

Technical Abstract: Polygalacturonase-inhibiting proteins (PGIPs) are leucine-rich repeat (LRR) proteins involved in plant defense. Sugar beet (Beta vulgaris L.) PGIP genes, BvPGIP1, BvPGIP2 and BvPGIP3, were isolated from two breeding lines, F1016 and F1010. Full-length cDNA sequences of the three BvPGIP genes encoded a 382 or 384 amino acid peptide. They shared closest similarity with five PGIP-like sequences found in the sugar beet reference genome (RefBeet 1.2.1) as well as Bv(FC607)PGIP1 and Bv(FC607)PGIP2 from sugar beet breeding line FC607. The predicted structure of BvPGIP1, 2 and 3 peptides was that of Phaseolus vulgaris PvPGIP2 with the exception that the sugar beet peptides were about 40 amino acids longer and encoded an additional LRR repeat. RT-PCR and qPCR analyses demonstrated BvPGIP gene expression in leaves, petioles, hypocotyls and highest expression in roots. Leaf and root BvPGIP transcripts increased in response to insect feeding and mechanical wounding. An agarose radial diffusion assay showed that BvPGIP protein extracts inhibited polygalacturonases (PGs) of Rhizoctonia solani, Fusarium oxysporum f. sp. gladioli and F. oxysporum f. sp. betae. PGIP extracts from line F1010 did not inhibit R. solani PGs. These findings indentify sugar beet PGIP genes that encode LRR domains that are longer than reported for most other species. In addition, the wound up-regulated BvPGIP gene expression and inhibition of fungal PGs by PGIP extracts suggest that like other plant PGIPs, the sugar beet genes play an active role in defense responses.