Abstract:

Sclerotinia sclerotiorum (Lib.) de Bary is the fungus that causes stem rot disease in oilseed rape. To overcome plant cell wall, during early pathogenesis, the fungus secretes several types of cell wall-degrading enzymes such as polygalacturonases (PGs). The activity of these enzymes is crucial for the colonization of plant tissues, and these enzymes can be determinants of pathogenicity or virulence. PG can activate defense reactions in plants, having no relation to the enzyme activity. In order to understand PG signaling pathway, PG gene was cloned from Sclerotinia sclerotiorum by RT-PCR, the encoding region of PG was fused to the yeast GAL4 DNA-binding domain in yeast expression vector PGBKT7 and an oilseed rape cDNA expression library was constructed in yeast. PG-interacting proteins were screened in the library with PG as bait by yeast two-hybrid assay. An interacting protein was isolated, sequencing and BLAST analysis revealed that the protein contains a C2-domain and was predicted to be a Ca²⁺ binding domain. The protein shares 80.24% identity in amino acids with a C2-domain protein in Arabidopsis with unknown function. The expression levels of the C2-domain protein in floral, leaf and stem organs of oilseed rape were investigated by semi-quantitative RT-PCR, the results showed that the C2-domain protein was highly expressed in leaves after induced by Sclerotinia sclerotiorum. Comparison in C2-domain proteins between oilseed rape and other species suggested that aspartatic acid residues involving in Ca²⁺ binding were conserved.

Key words:

Sclerotinia sclerotiorum, Polygalacturonase (PG), C2-domain