1.8.5
INVOLVEMENT OF PECTINASES FROM BOTRYTIS CINEREA IN PLANT PATHOGENESIS: CHARACTERIZATION, GENE EXPRESSION AND ELIMINATION OF THE ENCODING GENES

A TEN HAVE1, W OUDE BREUIL1, JP WUBBEN2, W MULDER2, J VISSER2 and JAL VAN KAN1

1Department of Phytopathology, Wageningen Agricultural University, Binnenhaven 9, 6709 PD Wageningen, The Netherlands; 2Section for Molecular Genetics of Industrial Micro-organisms, Wageningen Agricultural University, Dreijenlaan 2, 6703 HA Wageningen, The Netherlands

Background and objectives
Botrytis cinerea is a fungus that can infect over 200 plants, resulting in devastating pre- and post-harvest diseases of many agronomic crops. At all stages of the infection process, the fungus secretes cell wall-degrading enzymes which have been suggested to be involved in the penetration and the invasion of plant tissue [1]. As no reports are available on the isolation and characterization of the corresponding genes from B. cinerea, we have started a molecular analysis of these genes.

Results and discussion
We have isolated six members of the endopolygacturonase (endoPG) gene family, as described by Wubben et al., as well as an endo-pectin lyase. Expression studies, performed in several hosts at 20 and/or 4C, have shown a differential expression of the isolated genes. One of the endoPG encoding genes, Bcpg1, shows a basal expression both in planta and in liquid culture. Elimination of this gene, using gene replacement, resulted in a strain that: (i) shows a significantly reduced virulence, and (ii) shows a reduced induction of the remaining endoPG activities. Therefore we postulate that the activity of the gene product BcPG1 releases oligo-galacturonides that induce expression of (some) other endoPGs. We are therefore studying the expression of the endoPG gene family in both wild-type and the Bcpg1 null mutant by Northern blot, quantitative RT-PCR and IEF zymogram analysis. The latest results are presented and discussed with respect to both regulatory consequences and plant pathological aspects.

This research is supported by the Dutch Technology Foundation (STW), Grant no. WBI 33.3046.

References
1 Elad Y, Evensen K, 1995. Phytopathology 85, 637-643.