L-alanine induces programmed cell death in V. labrusca cell suspension cultures

Plant cell suspension cultures are reliable year-round sources of enzymes involved in secondary metabolite biosynthesis. Numerous studies have used V vinifera cell suspension cultures as an experimental system for studying these processes, while those from Concord grape (V labrusca L.) have been poorly exploited. V vinifera cell suspension cultures have been shown to grow well with casein hydrolysate (CH), which is a good source of reduced nitrogen in many tissue culture systems. The present report shows that V labrusca cell suspension cultures, in contrast to those of V vinifera, could only be established in the absence of CH as a source of reduced nitrogen. CH contains 20 amino acids, among which, the single amino acid L-alanine activates a programmed cell death response in V labrusca cells, as determined by terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) assay and propidium iodide nuclei staining. Programmed cell death was accompanied by the coordinated activation of phenylalanine ammonia lyase (PAL), cinnamic acid 4-hydroxylase (C4H), and stilbene synthase (STS) gene expression, as well as by the accumulation of stilbenes and other phenolic compounds. (c) 2006 Elsevier Ireland Ltd. All rights reserved.