ACID-GROWTH RESPONSE AND ALPHA-EXPANSINS IN SUSPENSION-CULTURES OF BRIGHT-YELLOW-2 TOBACCO

The possibility that Bright Yellow 2 (BY2) tobacco (Nicotiana tabacum L.) suspension-cultured cells possess an expansin-mediated acid-growth mechanism was examined by multiple approaches. BY2 cells grew three t imes faster upon treatment with fusicoccin, which induces an acidifica tion of the cell wall. Exogenous expansins likewise stimulated BY2 cel l growth 3-fold. Protein extracted from BY2 cell walls possessed the e xpansin-like ability to induce extension of isolated walls. In western -blot analysis of BY2 wall protein, one band of 29 kD was recognized b y anti-expansin antibody. Six different classes of alpha-expansin mRNA were identified in a BY2 cDNA library. Northern-blot analysis indicat ed moderate to low abundance of multiple alpha-expansin mRNAs in BY2 c ells. From these results we conclude that BY2 suspension-cultured cell s have the necessary components for expansin-mediated cell wall enlarg ement.