Genes involved in trehalose degradation including NTH1, NTH2, and ATH1 were also induced by ethanol. These observations also agreed with

previously reported [11, 12, 17, 29]. Enhanced expression of trehalose degrading genes appeared to be necessary in order to balance trehalose concentration and energy required for cell functions [11, 57]. As demonstrated in this study, rapid cell growth and highly integrated expression of genes involved in trehalose Blasticidin S concentration biosynthesis, glycolysis and pentose phosphate pathway were closely correlated for the ethanol-tolerant strain Y-50316. Continued enhanced expressions of many genes associated in these groups apparently contributed active energy metabolism (Figure 7). In addition, numerous genes able to maintain normal expressions in Y-50316 appeared to be important keeping gene interactive networks. These genes are necessary for the tolerant yeast to carry out the active metabolisms and complete the ethanol fermentation (Figure 7) while most of these genes were repressed for the parental strain Y-50049. The ethanol-tolerant Y-50316 was co-selected for inhibitor-tolerance derived from its parental Y-50049. Under the ethanol challenge, the ethanol-tolerant Y-50316 displayed tolerant gene expression

dynamics leading to similar route of pathway activities especially in every cofactor regeneration step. Cofactor NADPH plays an important role in biosynthesis of amino acids, lipids, and nucleotides [58, 59]. Under the ethanol stress condition described selleck compound in this study, the glucose metabolic pathways also appeared Alectinib having a well-maintained cofactor redox balance (Figure 7) as exampled for GND2 and ZWF1 in oxidative phase of pentose phosphate pathway, ALD4 in acetic acid production, and GCY1 in glycerol metabolism. Enhanced expression of ZWF1, SOL4, and YDR248C potentially provide sufficient substrate for a smooth pentose phosphate pathway flow. Therefore, sufficient NADPH supply likely contributes

ethanol tolerance indirectly through efficient biosynthesis of amino acids, lipids, and nucleotides for cell growth and function. Similarly, TDH1 involved in NADH regeneration step was highly induced. The enhanced expressions of alcohol dehydrogenase genes ADH1, ADH2, ADH3, ADH7, and SFA1, together with other normally expressed genes in the intermediate steps of glycolysis, are critical to complete the fermentation. For the above mentioned reasons, we consider tryptophan and proline synthesis genes TRP5, PRO1, and PUT1 as ethanol tolerance candidate genes. Our results support the involvement of these genes in ethanol-tolerance as suggested by previous studies [13, 25, 28]. Several genes involving in fatty acid metabolism were repressed except for ETR1, ELO1 and HTD2 having induced and normal expressions for the tolerant Y-50316.