EXPRESSION OF TWO SCLEROTINIA SCLEROTIORUM ENDOPG GENES CORRELATES WITH ENDOPOLYGALACTURONASE ACTIVITY DURING GLYCINE MAX COLONIZATION
L. Sella, A. Tomassini, R. D’Ovidio, F. Favaron
Quantitative expression of Sclerotinia sclerotiorum genes encoding two endo-polygalacturonase (endo-PG) isoforms (PGa and PGb), malate dehydrogenase (MDH, a key enzyme in fungal biosynthetic pathway of oxalic acid), and plant polygalacturonase-inhibiting protein (PGIP) were monitored by real-time reverse transcription- polymerase chain reaction (qRT-PCR) during the early stages (0-48 h) of soybean seedling infection. The activity of the two endo-PGs was also investigated during plant infection. PGa and PGb activity reflected very closely the pattern of their transcript accumulation as determined by qRT-PCR. In particular, the PGb encoding gene (Sspgb) was induced at 8 h after inoculation and reached a maximum at 16 h; expression of the PGa encoding gene (Sspga) was comparatively lower, reaching its maximum level later and its rate of increase paralleled that of the S. sclerotiorum b-tubulin gene; the expression of the MDH encoding gene (Ssmdh) was maximal 16 h after infection; soybean pgip transcript began to accumulate 8 h after inoculation reaching a maximum after 24 h. Expression patterns of reported genes are discussed in relation to the ability of S. sclerotiorum to induce disease by regulating endo-PGs and oxalate accumulation to elude the effect of plant PGIP.