Expression of grapevine chitinase genes in berries and leaves infected by fungal or bacterial pathogens

In order to study the involvement of chitinases in the interactions between grape berries and fungi, three genomic sequences encoding chitinases were isolated by PCR walking on Vitis vinifera DNA. Two of these belong to class I chitinases with a putative vacuolar (Vvchit 1a) and extracellular (Vvchit 1b) localization whilst the third sequence belongs to class III (Vvchit III). Transcripts of class III chitinases were shown to accumulate in unripe berries infected with Plasmopara viticola but not at later developmental stages of berries infected with Uncinula necator or Botrytis cinerea. In contrast, class I transcripts were never detected in grape berries. Specificity of chitinase expression in response to pathogens was investigated in leaves infected with B. cinerea or Pseudomonas syringae pv. pisi, a bacterium leading to an incompatible interaction. Expression of the Vvchit 1a gene was induced in leaves upon both infections. In contrast, accumulation of class III transcripts was observed in response to P. syringae but not to B. cinerea infection, whereas Vvchit 1b transcripts were detected in leaves only in the latter case. Our data indicate that, in V. vinifera, induction of chitinase genes depends on the infecting pathogen. (C) 2002 Elsevier Science Ireland Ltd. All rights reserved.