Two Brassica napus polygalacturonase inhibitory protein genes are expressed at different levels in response to biotic

Plants encode a distinct set of polygalacturon ase inhibitory proteins (PGIPs) that function to inhibit polygalacturonase enzymes produced by soft-rot fungal pathogens. We characterized two PGIP-encoding genes (Bnpgipl and Bnpgipl) from Brassica napus DH12075 (a double-haploid line derived from a cross between 'Cre sor' and 'Westar'). The two proteins exhibit 67.4% identity at the amino acid level and contain 10 imperfect leucine-rich repeats. The pgip genes are present as a small multigene family in B. napus with at least four members. Bnpgipl and Bnpgip2 are constitutively ex pressed in roots, stems, flower buds and open flowers. In mature leaf tissue, different levels of induction were observed in response to biotic and abiotic stresses. Bnpgipl expression was highly responsive to flea beetle feeding and mechanical wounding, weakly responsive to Sclerotinia sclerotiorum infection and exposure to cold but not to dehydration. Conversely, Bnpgip2 expression was strongly induced by S. sclerotiorum infection and to a lesser degree by wounding but not by flea beetle feeding. Application of jasmonic acid to leaves induced both Bnpgipl and Bnpgipl gene expression; however, salicylic acid did not activate either gene. Taken together, these results suggest that separate pathways regulate Bnpgipl and Bnpgip2, and that their roles in plant development or resistance to biotic and abiotic stress differ.