TABLE 4.

IMAx gene expression profiles in response to various carbon sources by RT-qPCR

Yeast strains were grown in YN medium containing 3% glycerol, 2% lactate, and 0.5% ethanol. Sugar (2% final concentration of maltose, αMG, isomaltose, galactose, or glucose) was then added to the culture medium when yeast cells reached the exponential phase (A_{600 nm} ∼ 1.0), and samples were collected after 1 h in the presence of the sugar. RNA levels were quantified by RT-qPCR as described under “Experimental Procedures.” Cultures were duplicated, and each of the RNA samples were then analyzed with two independent reverse transcription reactions. Four qPCR technical duplicates were therefore used for the calculation of expression data and their standard deviation. For each gene, the exponential phase sample before the addition of sugar (T0 control) was used as a calibrator sample (normalized fold expression set to 1). The MALx2 transcripts (both MAL12 and MAL32) were used as positive control for sugar induction or repression experiments. The transcripts of FBP1, which encodes fructose-1,6-bisphosphase, were used as an another positive control gene for glucose repression. Upper part: wild type CEN.PK113–7D strain; Lower part: mal2–8^c null mutant.

	MALx2	IMA1	IMA2	IMA3*a	IMA5	FBP1
Wild type
Control	1.0	1.0	1.0	1.0	1.0	1.0
Maltose	19.3 ± 4.6	55.0 ± 4.4	0.5 ± 0.2	1.4 ± 0.3	12.2 ± 3.2	NDb
αMG	5.7 ± 3.1	32.3 ± 4.1	1.2 ± 0.4	1.8 ± 0.2	29.7 ± 6.2	ND
Isomaltose	3.7 ± 1.9	36.8 ± 3.2	1.0 ± 0.3	1.4 ± 0.3	19.5 ± 1.0	ND
Galactose	0.4 ± 0.2	1.1 ± 0.3	0.9 ± 0.4	1.3 ± 0.5	1.1 ± 0.3	0.21
Glucose	0.03 ± 0	0.66 ± 0.1	0.31 ± 0.1	0.47 ± 0.3	1.26 ± 0.3	0.09
mal2–8c null mutant
Maltose	1.0	1.4	0.5	1.1	1.5	ND
αMG	1.1	1.2	0.7	0.9	1.6	ND
Isomaltose	1.5	0.9	0.6	0.6	1.2	ND

^a The star (★) represents the pool of IMA3 and IMA4 transcripts.

^b ND, not determined.