Sugar beet polygalacturonase-inhibiting proteins with 11 LRRs confer Rhizoctonia, Fusarium and Botrytis resistance in Nicotiana plants.

Polygalacturonase-inhibiting proteins (PGIPs) are leucine-rich repeat (LRR) proteins that inhibit polygalacturonase (PG) enzymes secreted by pathogens to break down plant cell walls during early stage of disease development. Sugar beet ( Beta vulgaris L.) PGIP genes ( BvPGIPs ) have 11 LRR domains as compared to 10 LRRs generally found in other plant species. To determine whether the BvPGIPs have a function in plant defense, genes encoding BvPGIP1 and BvPGIP2 that differ in 8 amino acids were fused with the CaMV 35S constitutive promoter and introduced into Nicotiana benthamiana . Crude PGIP protein extracts from BvPGIP1 transgenic plants significantly inhibited Rhizoctonia solani , Fusarium solani and Botrytis cinerea PGs. BvPGIP2 extract also inhibited PGs from F. solani and B. cinerea but did not inhibit PGs from R . solani . When transgenic BvPGIP plants were bioassayed for resistance, similar results were obtained. This is a first report that documents sugar beet PGIPs with 11 LRRs confer resistance to three different fungal pathogens. [ABSTRACT FROM AUTHOR]