Overview of gene selection criteria. Transcript profiles of genes that specifically respond to low nitrogen (A) and to N starvation (B) under alcoholic fermentation conditions; results, log₂ expression ratios obtained by dividing the experimental results by the reference sample results, are represented with a green-to-red color scale. Each expression diagram shows, from top to bottom, relative expression levels of each set of genes and, from left to right, comparisons between LN24, CF48, CF96, LN48, LN80, LN96, and LN144 and the reference cultures, CF24. Down-regulated genes are green, whereas up-regulated genes are red.

Validation of macroarray data obtained with S. cerevisiae PYCC4072 by semiquantitative RT-PCR. Panel A shows a histogram corresponding to the results obtained with macroarray analysis, relative to PDA1 results. Panel B contains the result of the semiquantitative RT-PCR analysis carried out with samples from two independent cultures.

Analysis of some of the candidate genes in S. cerevisiae strain ICV 16 (Fermicru primeur, DSM). Panel A shows the changes in extracellular nitrogen concentrations (⧫) and yeast cell growth (×) versus glucose consumption (○) during fermentation with an initial assimilable-nitrogen concentration of 60 mg liter⁻¹. Data presented are representative of at least three independent experiments. Panel B contains the results obtained by RT-PCR. CF24, sample from control fermentation carried out with 300 mg N/liter at 24 h after inoculation, when the amount of assimilable nitrogen remaining in the must was 260 mg liter⁻¹ (9); LN72 and LN144, samples obtained at 72 and 144 h, respectively, from the nitrogen-limiting fermentation; RF, sample obtained 9 h after addition of nitrogen to the limiting vinification. OD, optical density.