Glucose, Nitrogen, and Phosphate Repletion in
Saccharomyces cerevisiae: Common Transcriptional
Responses to Different Nutrient Signals
Michael K. Conway, Douglas Grunwald, and Warren Heideman1
Pharmaceutical Sciences, School of Pharmacy, University of Wisconsin, Madison, Wisconsin 53705
ABSTRACT Saccharomyces cerevisiae are able to control growth in response to changes in nutrient avail-
ability. The limitation for single macronutrients, including nitrogen (N) and phosphate (P), produces stable
arrest in G1/G0. Restoration of the limiting nutrient quickly restores growth. It has been shown that glucose
(G) depletion/repletion very rapidly alters the levels of more than 2000 transcripts by at least 2-fold, a large
portion of which are involved with either protein production in growth or stress responses in starvation.
Although the signals generated by G, N, and P are thought to be quite distinct, we tested the hypothesis
that depletion and repletion of any of these three nutrients would affect a common core set of genes as part
of a generalized response to conditions that promote growth and quiescence. We found that the response
to depletion of G, N, or P produced similar quiescent states with largely similar transcriptomes. As we
predicted, repletion of each of the nutrients G, N, or P induced a large (501) common core set of genes and
repressed a large (616) common gene set. Each nutrient also produced nutrient-specific transcript changes.
The transcriptional responses to each of the three nutrients depended on cAMP and, to a lesser extent, the
TOR pathway. All three nutrients stimulated cAMP production within minutes of repletion, and artificially
increasing cAMP levels was sufficient to replicate much of the core transcriptional response. The recently
identified transceptors Gap1, Mep1, Mep2, and Mep3, as well as Pho84, all played some role in the core
transcriptional responses to N or P. As expected, we found some evidence of cross talk between nutrient
signals, yet each nutrient sends distinct signals.
protein kinase A
Yeast starved for macronutrients, such as glucose (G), nitrogen (N), or
phosphorous (P), arrest growth and cell division and become quies-
cent, with cell wall thickening, reduced transcription and translation,
and increased stress tolerance (Gray et al. 2004; Rowley et al. 1993).
Upon nutrient repletion, yeast immediately return to growth and di-
vision (Unger and Hartwell 1976).
Glucose addition to starved, quiescent yeast rapidly alters the
expression of more than a third of the yeast genome by at least 2-fold
(Martinez et al. 2004; Radonjic et al. 2005; Slattery and Heideman
2007; Wang et al. 2004). Genes needed for ribosome biogenesis (RiBi),
ribosomal proteins (RP) translation, mass accumulation, and cell di-
vision are induced (Jorgensen et al. 2004). In contrast, environmental
stress response (ESR) (Gasch et al. 2000), gluconeogenic, respirative,
and alternative metabolism genes are repressed.
This large-scale change depends on the Gpa2 G-protein asso-
ciated with the Gpr1 glucose receptor (Santangelo 2006; Wang
et al. 2004). The response is also largely dependent on cAMP pro-
duction, as well as a functional TOR pathway (Slattery et al. 2008).
Glucose produces this massive rearrangement of the transcriptome,
even in cells lacking the ability to take up and metabolize glucose
(Slattery et al. 2008). These results point to a cell surface receptor-
Most study of nutrient sensing in S. cerevisiae has focused on
specific metabolic challenges, such as glucose repression or regulation
of amino acid synthesis. Thus, we have limited knowledge of how
these different nutrients cause cells to return to growth (Forsberg
and Ljungdahl 2001; Magasanik and Kaiser 2002; Wykoff and O’Shea
2001; Zaman et al. 2008).
Copyright © 2012 Conway et al.
Manuscript received April 18, 2012; accepted for publication June 20, 2012
This is an open-access article distributed under the terms of the Creative
Commons Attribution Unported License (http://creativecommons.org/licenses/
by/3.0/), which permits unrestricted use, distribution, and reproduction in any
medium, provided the original work is properly cited.
Supporting information is available online at http://www.g3journal.org/lookup/
1Corresponding author: School of Pharmacy, University of Wisconsin, 777 Highland
Avenue, Madison, WI 53705. E-mail: firstname.lastname@example.org
Volume 2| September 2012|
Work from Thevelein et al. (2005) has shown a role in trehalase
activation for cell surface N and P sensors that is largely dependent
on PKA. Because these proteins needed for trehalase stimulation
also serve as nutrient transporters, they have been termed transceptors
(Donaton et al. 2003; Popova et al. 2010; Van Zeebroeck et al. 2009).
One such transceptor is the Gap1 amino acid transporter (Jauniaux
and Grenson 1990; Magasanik and Kaiser 2002). Trehalase activation
by amino acids is Gap1-dependent. A similar finding was made in
studying the role of the Pho84 phosphate transporter. Phosphate
activation of trehalase activation is Pho84-dependent (Popova et al.
2010). Finally, the Mep family of ammonium transporters are impor-
tant for ammonium stimulation of trehalase activity (Van Nuland
et al. 2006).
Because the states of quiescence and growth appear have require-
ments that are the same regardless of the missing nutrient, we hy-
pothesized that N, P, and G depletion and repletion would control
large common gene sets needed for growth and quiescence. In this
article, we confirm this hypothesis and show that all three nutrients
produce responses that are similar in appearance and share common
mechanisms. While the initial signals appear to come from different
receptors, including Gpr1, Gap1, Pho84, and Mep proteins, the nu-
trient signals produce a response that is largely cAMP-dependent.
Furthermore, all three nutrients elevate cAMP levels when repleted.
These results indicate that different nutrient signals converge to con-
trol common states of quiescence and growth.
MATERIALS AND METHODS
Yeast strains and growth media
S288C (MATa SUC2 gal2 mal mel flo1 flo8-1 hap1 ho bio1 bio6) was
used for glucose, nitrogen, and phosphate experiments. TC41-1
(MATa leu2-3 leu2-112 trp1-1 his3-532 his4 cyr1::URA3 cam) and
the isogenic CYR1+ wild-type HR125 were used for PKA and TOR
nutrient repletion experiments (Heideman et al. 1990). BY4742
(MATa his3D1 leu2D0 lys2D0 ura3D0) was used for transceptor work
as wild-type and gap1D and pho84D mutants made in BY4742 were
from the yeast knockout collection obtained from Open Biosystems,
with either gene deleted by KanMX. Deletions were confirmed by
Cells were grown in YPD (1% yeast extract, 2% peptone, 2% glucose,
Sunrise Chemicals) or synthetic medium (SD) with 2% glucose
containing 6.7 g/l yeast nitrogen base (US Biological) supplemented
with adenine, uracil, and amino acids. Cells were cultured at 30? with
shaking. Nitrogen deprivation medium (SD-N) consisted of SD made
up with nitrogen-free Yeast Nitrogen Base (Difco) and without amino
acids or uracil. Phosphate deprivation medium (SD-P) consisted of SD
made with yeast nitrogen base in which potassium chloride was
substituted for potassium phosphate. Rapamycin (10 mg/ml stock in
ethanol, LC Laboratories) and cAMP (1M stock in water, pH 7,
Sigma) treatments were as described previously (Newcomb et al.
2003; Russell et al. 1993; Slattery et al. 2008). When added, cAMP
was used at 1 mM and rapamycin at 200 nM.
Glucose depletion was as previously described (Slattery and Heideman
2007). Cells were grown in SD medium for 48–72 hr until they had
arrested as a quiescent G1 phase population. Nitrogen starvation was
achieved by inoculating cells from an overnight SD culture into SD-N
at a density of 0.4 OD660. When growth stopped (24 hr, approximately
1.5 OD660), cells were transferred to a fresh volume of SD-N to a den-
sity of 0.5 OD660. These cells were incubated an additional 24 hr and
generally reached a density of OD6600.75–1. Finally, this culture was
resuspended in fresh SD-N at OD660of 1.0 and incubated for 12–
24 hr. Depletion was confirmed by determining that cells would not
proliferate in fresh SD-N but would grow in SD. Phosphate depletion
was carried out in the same manner, except that phosphate depletion
medium was used. In both cases, nutrient repletion was accomplished
by pelleting in a Beckman J6 centrifuge at 30? at 2500 rpm for 5 min
and resuspension in an equivalent volume of fresh SD medium.
For dual nutrient depletion experiments, cultures were grown in
N- or P-free medium until they ceased dividing and were then
transferred to medium also lacking G and incubated for an additional
48 hr to deplete any glucose remaining in the medium. This
produced GN- and GP-depleted cells; we confirmed that repletion
of only a single nutrient did not produce growth (data not shown).
The pho84D cells were starved for P as described above and chal-
lenged with KH2PO4or Gly3P (both 10 mM). The Gap1 cells were
nitrogen depleted as described above and repleted with SD-N with 10
mM L-citrulline added. The MEP-deletion strains were N-depleted as
described above and repleted by addition of SD-N plus 10 mM am-
The cyr1D strain TC41 was nutrient depleted using the techniques
previously described (Slattery and Heideman 2007), in which the
nutrient depletion followed the schedule described above except that
during nutrient the first 24 hr of depletion the cells were cultured with
1 mM cAMP and 0.5· auxotrophic supplements to be certain that the
cells could remain growing enough to deplete the missing macronu-
trient. This was followed by 24 hr in depletion medium with 1 mM
cAMP and by an additional 24 hr with no cAMP. This procedure was
used to avoid halting growth and metabolism prematurely by cAMP
withdrawal before true nutrient depletion had occurred.
Twenty-five optical density (OD) units of cells were harvested into ice-
cold TCA to a final concentration of 5% and vortexed briefly to mix.
The lysates were neutralized with NaHCO3to pH ?6.5–7 and snap-
frozen on liquid nitrogen. Immediately prior to assay, samples were
thawed on ice and centrifuged at 4? for 1 min, and then 20 mL of
supernatant was used in the R&D Systems cAMP Parameter Assay Kit
(KGE002B) as indicated by the manufacturer.
RNA isolation and microarray hybridization
Samples of cells were collected in independent experiments to produce
true biological replicates. For these experiments, cultures from in-
flasks to nutrient limitation as described above. In some cases, duplicate
cultures were grown on separate days, and in others, the cultures were
grown in the same shaker started on the same day. Samples were kept
separate, and the results from the duplicates are shown.
For each hybridization, 10 ODU cells were collected and pelleted at
5000 RPM in a Beckman J6 centrifuge for 2 min at 30?. Then the
supernatant was removed and the pellets were frozen with liquid
RNA was isolated using MasterPure Yeast RNA Purification Kits
(Epicentre Technologies), and the quality was assayed by gel
electrophoresis. cRNA synthesis was carried out using the GeneChip
Expression 39 Amplification One-Cycle Target Labeling and Control
Reagents kit from Affymetrix following the manufacturer’s instruc-
tions. cRNA samples were hybridized to GeneChip Yeast Genome 2.0
Arrays for 16 hr. Arrays were washed, stained, and scanned according
|M. K. Conway, D. Grunwald, and W. Heideman
to the manufacture’s recommendation. Affymetrix .CEL files were
RMA normalized with R and the Bioconductor Suite (Gentleman
et al. 2004). Data analysis was performed within TIGR Multiexperi-
ment Viewer, v4.5.1 (Saeed et al. 2003; 2006), in-house Perl scripting,
R, and Bioconductor.
Genes that were differentially expressed between the fed and
starved states from each nutrient condition were selected using the
following criteria: a P value less than 0.05; a false discovery rate less
than 0.01 (q-value); and a 2-fold change in expression. The individual
nutrient lists were compared to identify the genes in common, as well
as those unique to each combination, resulting in the Venn diagrams
shown in Figures 3 and 4 and supporting information, Table S1 and
GO enrichment analysis was performed through FUNSPEC tool
(Robinson et al. 2002) at http://funspec.med.utoronto.ca/. Under- and
overrepresented DNA motifs were identified using the RSAT online
motif discovery tool at http://rsat.ulb.ac.be/ (van Helden 2003), where
oligomer length was scanned between 4 and 8 bases and the best-
consensus sequence scores were collected. Transcription factor target
and motif enrichment significance were calculated using a hypergeo-
metric distribution test.
Different nutrient limitations produce
a similar transcriptome
Starvation for glucose (G), nitrogen (N), or phosphate (P) each
2000; Giots et al. 2003; Gray et al. 2004; Johnston et al. 1977; Mazon
1978). This leads to the idea that while the signals from these nutrients
are distinct, they converge in some way to control quiescence and
We first compared transcripts in yeast starved for G, N, or P.
Prototrophic S288C cells were transferred from complete medium to
synthetic medium lacking G, N, or P and incubated until they had
arrested growth as described in Materials and Methods. Total RNA
was isolated and used to probe Affymetrix microarrays. The experi-
ments were conducted using duplicate yeast cultures started from
separate colonies. Paired biological replicate signal intensities for each
mRNA for each starvation condition are shown as a heat map (Figure
1A). In this arrangement, genes at the top of the map with the bright-
est color have the highest hybridization signals, whereas those at the
bottom had the lowest. Replicate experiments are shown side by side,
but in most cases, the replicate values were so similar that they cannot
be visually distinguished.
Qualitatively, the heat map in Figure 1A indicates that all three
nutrient limitations produce regions of strong similarity in transcript
abundance pattern; with the G-depleted samples somewhat distinct
from the N- and P-depleted samples. We calculated Pearson correla-
tion coefficients and produced linear regression plots to compare the
patterns of transcript abundances produced by each type of depletion
(Figure 1B). Each transcript is plotted as a dot positioned with its
abundance in one nutrient condition plotted on the Y-axis, and abun-
dance in the other nutrient condition on the X-axis. Overall, there was
high correlation between the three starvation states (Chua et al. 2006;
Grigull et al. 2004), but as noted, the responses to N and P limitation
were more similar to each other than either was to the response pro-
duced by G limitation. Comparison of the N and P starvation
responses produced a correlation of 0.93, whereas comparison of G
limitation to N and P starvation yielded Pearson correlations of 0.79
and 0.77 respectively.
In general, these results indicate that the quiescent states produced
by the separate nutrient limitations are quite similar in terms of global
gene expression, a conclusion recently reported by Klosinska et al.
(2011). Although we used an S288C strain and Broach and co-workers
in that study used a W303 derivative, both experiments yielded similar
results. Comparing our single time point values with the published
results, we found the highest correlations to their 5760 (96 hr) time
Figure 1 Comparing transcript levels in G-, N-, or P-depleted cells.
Wild-type (S288C) cultures were transferred into S medium lacking G,
N, or P and were cultured until growth was arrested, and then samples
were collected for Affymetrix microarray analysis as described in
Materials and Methods. (A) Heat map plotting normalized log2-
transformed hybridization intensity data for G-, N-, and P-limited sam-
ples arranged by k-means clustering. Independent biological replicate
samples are shown as side-by-side columns; the values are so similar
between replicates that these columns cannot be readily distinguished
by eye in most cases. (B) For each transcript, average intensity data
from (A) is plotted such that the expression level in one nutrient con-
dition is on the X-axis, and intensity value in another condition is on
the Y-axis. G vs. N starvation yielded a Pearson correlation of 0.79;
G vs. P starvation a correlation of 0.77; and N compared with P, a
correlation of 0.92.
Volume 2 September 2012|Growth Response to Nutrients in Yeast|
point samples, with Pearson correlations of 0.78, 0.75, and 0.64 be-
tween the G-, N-, and P-depletion results, respectively.
Nutrient repletion triggers massive changes
in transcript abundance
The cellular pathways for sensing G, N, or P are thought to be quite
distinct (Santangelo 2006; Schneper et al. 2004; Zaman et al. 2008).
Yet, repletion of each of these nutrients causes growth, protein
synthesis, and reversal of quiescence. We hypothesized that repletion
of each nutrient would produce a set of transcriptional changes
overlapping those produced by G (Radonjic et al. 2005; Slattery and
Heideman 2007; Wang et al. 2004).
To test this, we added back the limiting nutrient to quiescent G-,
N- or P-depleted S288C cells and collected samples for microarray
analysis at 60 min. By 90 min, cells had begun to produce buds,
indicating a return to growth (not shown). Figure 2A shows the
changes in gene expression produced by each nutrient, expressed as
fold change (log2) relative to quiescent samples. Red indicates in-
creased expression, and green indicates repression caused by nutrient
Large groups of genes were upregulated by all three nutrient
repletions, as revealed by clusters toward the top of the figure, whereas
other groups, shown toward the bottom, were downregulated by all
three repletions. Other gene sets were nutrient-specific.
As with the data in the first figure, we used dot plots to compare
the fold change induced by one nutrient with the changes induced by
another (Figure 2B). As before, the similarities between the responses
were reflected in the correlation coefficients, and the N- and P-
repletion responses were more similar to each other than they were
to the G response. N and P repletion produced responses with a cor-
relation of 0.82, whereas the response to N repletion produced a cor-
relation coefficient of 0.69 compared with the response to G.
Comparison of the responses to G and P repletion produced a corre-
lation of 0.67.
Growth genes are upregulated by all three nutrients
To identify a core set of genes induced in response to all three
nutrients, we selected sets of genes that were induced by each of the
nutrient repletions. These sets were made up of transcripts that met
the following criteria: P , 0.05, a false discovery rate (q-value) less
than 0.01, and at least a 2-fold induction by the nutrient repletion
(log2 ratio greater than or equal to 1).
This arbitrary cutoff yielded the following gene sets: 1601 increased
by glucose; 877 increased by nitrogen; and 1003 increased by
phosphate. Of the genes upregulated by both nitrogen and phosphate,
83% (P , 2.139 · 102257) were also upregulated by glucose, pro-
ducing an overlapping set of 501 genes induced by each of the three
nutrients (Figure 3).
This common set of 501 genes was greatly enriched for protein
synthesis genes. GO functional classification showed significant enrich-
ment for rRNA processing (,1e214), tRNA processing (,1e214),
ribosome biogenesis (,1e214), rRNA synthesis (,1.84e212), and re-
lated growth functions (Table 1). This set was also significantly enriched
for genes mapping to the nucleolus (,1e214), a key site for ribosome
development. Of the 236 recognized RiBi transcripts we measured, 160
(67%, P , 1.145e2117) were found in this common cluster (Jorgensen
et al. 2004). G, N, and P repletions all induced ribosomal protein (RP)
transcripts; however, the fold induction by G averaged well above the
2-fold cutoff, while for most RP genes, induction by N or P fell slightly
below this cutoff (Table S1).
We also looked for short over-enriched motifs within promoter
regions of each gene in each cluster using RSAT, an online motif
discovery tool for de novo promoter enrichment analysis (Thomas-
Chollier et al. 2008; van Helden 2003). In a related search, we exam-
ined transcription factor target enrichments and binding sequence
Figure 2 Large-scale transcriptional responses to G, N, and P re-
pletion. Wild-type (S288C) cells were starved for G, N, or P until
growth was arrested as in Figure 1, and then the missing nutrient was
repleted as described in Materials and Methods. Samples for micro-
array analysis were taken at the nutrient-limited state and 60 min after
repletion of each missing nutrient. (A) Heat map showing the log2 fold
change for each gene, comparing the nutrient repleted with the initial
quiescent samples. Independent biological replicate samples are
shown as side-by-side columns, and the transcripts are arranged by
k-means clustering. Red indicates increased expression; green indi-
cates reduced. (B) For each transcript, fold change data from (A) is
averaged and plotted such that the fold change in response to one
nutrient condition is on the X-axis, and the fold change in response to
another nutrient is plotted on the Y-axis. The red diagonal line indi-
cates the linear regression: G compared with N repletion yielded
a Pearson correlation of 0.69, whereas compared with P, yielded
0.67. N vs. P repletion had a correlation of 0.83.
| M. K. Conway, D. Grunwald, and W. Heideman
enrichments based on previous genome-wide studies (Macisaac et al.
2006; Robert et al. 2004; Zhu et al. 2009). These enrichments are
summarized in Table 1. We find the set of 501 genes induced in
common by G, N, and P to be significantly enriched for RRPE
(AAAWTTTT) and PAC (GATGAG) elements (Dequard-Chablat
et al. 1991; Hughes et al. 2000; Slattery and Heideman 2007). Of
the 501 G-, N-, and P-induced genes, 64% (P , 2.3e285) contain at
least one RRPE, 53% (P , 6.17e244) at least one PAC, and approx-
imately 42% (P , 3.67e290) contain both an RRPE and a PAC. This is
not surprising in that a connection between genes induced by G re-
pletion and the presence of PAC and RRPE elements has previously
been made (Fingerman et al. 2003; Hughes et al. 2000; Slattery and
Heideman 2007; Wade et al. 2001).
Nutrient-specific differences: genes not upregulated
In addition to genes displaying a common response, we anticipated
nutrient-specific expression patterns. A set of 780 genes met our
criteria for G induction, but not for N or P. These transcripts induced
2-fold specifically by G repletion showed a connection to growth
metabolism, perhaps distinct from the N and P sets because of the
dual energy and carbon source potential provided by G. This set was
significantly enriched for RP genes (P , 1.42e214), containing 97 of
the 137 RP genes (P , 3.83e252). As mentioned above, the RP genes
were also significantly induced by N or P repletion, but they failed to
pass the 2-fold cut off. On closer examination, we found that the RP
transcripts had the greater fold induction in G largely because of
a greater repression during G starvation (See Discussion and Figure
S1). In this G-induced set, we found enrichment for gene targets for
Rap1, Fhl1, and Sfp1, regulators of RP transcription, and we also found
enrichment for their corresponding binding motifs (Fingerman et al.
2003; Lieb et al. 2001; Marion et al. 2004; Pina et al. 2003; Schawalder
et al. 2004). GO enrichments were also observed for translation-related,
protein-trafficking, and ER-localization functions (Table 1).
As might be expected, the subset of 115 N-induced genes was
enriched for genes involved with amino acid biosynthesis and
nitrogen metabolism. This set was enriched for targets bound by
Gcn4, Bas1, Met32, Met4, and Cbf1, and it was also enriched for their
binding sequence motifs (Table 1).
The 183 genes specifically induced by P were less obviously
connected with P metabolism by GO enrichment analysis, appearing
enriched for transcriptional control and DNA binding (Table 1). Ino4
and Ino2 targets are enriched, suggesting a need for phospholipid syn-
thesis after P deprivation, an observation noted previously (Greenberg
and Lopes 1996).
Stress genes are downregulated by all three nutrients
We used the cutoff screen described above to identify a set of 616 genes
downregulated in common by G, N, or P (Figure 4). Each nutrient
decreased the expression of a large group of stress-related genes. Func-
tional classifications showed significant enrichment in the following
groups: oxidative stress response (P , 6.32e29), heat shock response
(P , 3.16e27), autoproteolytic processing (P , 1.07e206), metabolism
of energy reserves (P , 3.1e25), and autophagy (P , 1e214) (Table 2).
We also found this set enriched for peroxisome (P , 6.65e29) and
vacuolar lumen concentration (P , 9.5e24). Perhaps most noteworthy,
this set also contains 197 of the approximately 272 (P , 1.07e2134)
environmental stress response (ESR) genes originally identified by
Gasch et al. (2000). Consistent with this, the group is enriched for
STRE elements (Martinez-Pastor et al. 1996) in the 59 intragenic
regions (Table 2). This group is also enriched for Hsf1, Msn2, and
Msn4 targets important for stress gene regulation (Gasch et al. 2000).
We found 537 genes downregulated by G repletion but not N or P.
This group was enriched for sugar transport (P , 3.15e28), aerobic
respiration (P , 3.5e24), transcriptional control (P , 1.92e28), and
homeostasis of metal ions (P , 2.6e24). This cluster was enriched for
gene products localizing to the mitochondrial inner membrane, con-
sistent with GO enrichment for aerobic respiration. Gal4, Hap1, Sok2,
and Sut1 targets were also enriched in this set, and motifs for Mig1
and Rtg3 were enriched in the 59 intragenic regions (Table 2).
The 136 genes specifically downregulated by N alone were
enriched for catabolism of nitrogenous compounds (P , 8.29e25)
and amino acid/amino acid derivative transport. While this set was
enriched for nitrogen catabolite repression (NCR) genes (P , 1.9e29),
the majority of NCR genes were found in the set repressed in common
by G, N, and P, an observation in concordance with the fact that many
NCR genes are elevated in starvation (Wu et al. 2004). Finally, the 59
intragenic regions of this cluster were enriched for Stp1, Gln3, Bas1,
Gat1 binding targets, and their corresponding sequence motifs.
Figure 3 Genes induced by G, N, and P repletion. Microarray data
from Figure 2 was used to identify genes induced at least 2-fold by G,
N, or P repletion using cutoffs described in Materials and Methods.
The Venn diagram shows the intersections between the sets of genes
induced at least 2-fold by each nutrient. This intersection of three sets
produced seven different groups, and a heat map of fold-change
responses is shown for each of these seven sets. Independent biolog-
ical replicate samples are shown as side-by-side columns, and the
transcripts are arranged by k-means clustering. The number of individ-
ual transcripts in each set is shown in the figure, and the transcripts are
listed for each set in Table S1.
Volume 2September 2012|Growth Response to Nutrients in Yeast|