Parrou J L, Enjalbert B, Plourde L, Bauche A, Gonzalez B, François J
Centre de Bioingenierie Gilbert Durand, UMR-CNRS 5504, LA. INRA, INSA, Complexe Scientifique de Rangueil, Toulouse, France.
Yeast. 1999 Feb;15(3):191-203. doi: 10.1002/(SICI)1097-0061(199902)15:3<191::AID-YEA358>3.0.CO;2-O.
The dynamic responses of reserve carbohydrates with respect to shortage of either carbon or nitrogen source was studied to obtain a sound basis for further investigations devoted to the characterization of mechanisms by which the yeast Saccharomyces cerevisiae can cope with nutrient limitation during growth. This study was carried out in well-controlled bioreactors which allow accurate monitoring of growth and frequent sampling without disturbing the culture. Under glucose limitation, genes involved in glycogen and trehalose biosynthesis (GLG1, GSY1, GSY2, GAC1, GLC3, TPS1), in their degradation (GPH1, NTHI), and the typical stress-responsive CTT1 gene were coordinately induced in parallel with glycogen, when the growth has left the pure exponential phase and while glucose was still plentiful in the medium. Trehalose accumulation was delayed until the diauxic shift, although TPS1 was induced much earlier, due to hydrolysis of trehalose by high trehalase activity. In contrast, under nitrogen limitation, both glycogen and trehalose began to accumulate at the precise time when the nitrogen source was exhausted from the medium, coincidentally with the transcriptional activation of genes involved in their metabolism. While this response to nitrogen starvation was likely mediated by the stress-responsive elements (STREs) in the promoter of these genes, we found that these elements were not responsible for the co-induction of genes involved in reserve carbohydrate metabolism during glucose limitation, since GLG1, which does not contain any STRE, was coordinately induced with GSY2 and TPS1.
研究了储备碳水化合物对碳源或氮源短缺的动态响应，以便为进一步研究酿酒酵母在生长过程中应对营养限制的机制特征奠定坚实基础。本研究在控制良好的生物反应器中进行，该反应器能够在不干扰培养物的情况下精确监测生长情况并频繁取样。在葡萄糖限制条件下，当生长离开纯指数期且培养基中葡萄糖仍充足时，参与糖原和海藻糖生物合成（GLG1、GSY1、GSY2、GAC1、GLC3、TPS1）、降解（GPH1、NTHI）的基因以及典型的应激反应CTT1基因与糖原同时被协同诱导。海藻糖的积累延迟到双相转变期，尽管TPS1诱导得更早，但由于高海藻糖酶活性导致海藻糖水解。相反，在氮限制条件下，当培养基中的氮源耗尽时，糖原和海藻糖开始同时积累，这与参与它们代谢的基因的转录激活同时发生。虽然这种对氮饥饿的反应可能是由这些基因启动子中的应激反应元件（STREs）介导的，但我们发现这些元件并不负责葡萄糖限制期间参与储备碳水化合物代谢的基因的共诱导，因为不包含任何STRE的GLG1与GSY2和TPS1被协同诱导。
