SILICON-RESPONSIVE CDNA CLONES ISOLATED FROM THE MARINE DIATOM CYLINDROTHECA-FUSIFORMIS

In organisms ranging from single-celled algae to mammals, including hu mans, silicon is essential for, and actively participates in, a variet y of life processes. It has become clear that silicon (i) acts as a me tabolite affecting a variety of cellular processes, and (ii) regulates gene expression. However, the mechanisms by which silicon (i.e., Na2S iO3.9H(2)O, in the present study) acts are not clear, due to inherent methodological difficulties. As part of our program to understand how silicon acts in biological systems, we present the first isolation of cDNA clones derived from silicon-responsive mRNAs, from the marine dia tom Cylindrotheca fusiformis. We distinguish between clones responding only to silicon starvation and replenishment, and those also respondi ng to other cellular conditions. Some of the clones can be identified by similarity to other genes, and should be useful as probes to isolat e genes from other organisms. Isolation of these clones provides the m eans to (i) identify metabolic pathways affected by silicon, and (ii) investigate the mechanism(s) of silicon-regulated gene expression.