Proteases for the Improvement of Plant Transformation

Abstract

Embryogenic cell lines of Vitis vinifera cv. Ugni Blabc (UB), co-cultivated with different strains of Agrobacterium tumefaciense undergo necrogenesis leading subsequently to cell death. Antioxidants that were previously utilized in grape transformation (Perl et al. 1996) were found to have only a limited effect blocking this necrogenesis. We assumed that this necrogenesis is due to a hypersensitive like response (HR) of the embryogenic lines to Agrobacterium tumefaciens. If a putative proteinaceous elicitor is responsible for inducing the HR-like response in UB embryogenic cell lines, then treatments with certain proteases might reduced this necrogenesis (Wei et al 1992). Ion channels were recently reported to initiate signal transduction in higher plants including during bacterial attack (Ward et al 1995). Channel blockers like lanthanum and k-252a were previously shown to inhibit the HR response of tobacco cells elicited by harpin — a protein excreted by several bacteria during the pathogenesis process (Wei et al 1992; He et al 1993; 1994; Bauer et al 1995). The plant growth regulator, jasmonic acid (JA) has been shown to induce a similar HR-like necrogenesis when applied to the growth of our embryogenic cell lines (Perl et al in preparation). Aspirin or related benzoic compounds were shown to repress gene expression activated by JA (Pena-Cortes et al. 1993; Doherty et al. 1988). In animal systems, almost all aspirin-like drugs inhibit the cylooxygenase activity of the enzyme prostaglandin endoperoxidase synthase (Smith and Marnett). Prostaglandins and the phytohormone JA display some similarity in both chemical structure and biosynthetic pathways (Needleman et al. 1996).