Impact of nutrients and stress, including antifungal drugs, on growth and ribosomal content in Saccharomyces cerevisiae [article]

Nahuel Manzanaro Moreno, University Of Edinburgh, Peter Swain
Ribosomes are the machines that produce proteins in the cell. They are, with histones, the most expressed proteins, accounting together for almost half of the total gene expression. Ribosome number varies with growth rate, the energy state of the cell, and with the cell cycle. Bacterial cells express more ribosomes the higher their growth rate; the number will also increase when there is an inhibitor of translation present. In contrast to ribosomal genes, constitutive genes show a decrease in
more » ... pression with growth rate, as cells prioritize ribosome and histone genes. Although these results are well established in bacteria, they are much less so in eukaryotic cells. The aim of this thesis was to determine if the eukaryote budding yeast behaved similarly to Escherichia coli and obeyed the same phenomenological relationships. First, a reliable way to modulate growth rate without the use of drugs is by changing the concentration of carbon source, but yeast grows slowly only in prohibitively low concentrations of glucose, the typical carbon source. Raffinose is a poorly fermented trisaccharide. Here I show that it follows a gentle Monod curve, increasing growth rate steadily with the increase in concentration and plateauing only at high concentrations. I argue that it is the sugar of choice for tuning the growth rate in yeast. Second, I explore orthogonal induction systems in yeast with the goal of causing competition for translational resources. I conclude that the inducer doxycycline is deleterious in respiring yeast likely because of adverse effects on the mitochondria. Third, I wanted to determine the behaviour of constitutively expressed genes as a function of growth rate as a benchmark for the measurement of ribosomal expression. Using a set of reported constitutive promoters controlling the expression of fluorescent proteins, cells were grown at different rates to measure expression at the point of maximal growth rate. I conclude that constitutive expression typically shows a moderate decrease in expression at [...]
doi:10.7488/era/1687 fatcat:4iskf4ykpvgcdelzwmx54mdvj4