Candida albicans Infection of ...

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CandidaalbicansInfection of Caenorhabditiselegans
Induces Antifungal Immune Defenses
Read Pukkila-Worley
1,2,3
, Frederick M. Ausubel
2,3
*
.
, Eleftherios Mylonakis
1,4
*
.
1 Division of Infectious Diseases, Massachusetts General Hospital, Boston, Massachusetts, United States of America, 2Department of Molecular Biology, Massachusetts
General Hospital, Boston, Massachusetts, United States of America, 3 Department of Genetics, Harvard Medical School, Boston, Massachusetts, United States of America,
4 Harvard Medical School, Boston, Massachusetts, United States of America
Abstract
Candida albicans yeast cells are found in the intestine of most humans, yet this opportunist can invade host tissues and
cause life-threatening infections in susceptible individuals. To better understand the host factors that underlie susceptibility
to candidiasis, we developed a new model to study antifungal innate immunity. We demonstrate that the yeast form of C.
albicans establishes an intestinal infection in Caenorhabditis elegans, whereas heat-killed yeast are avirulent. Genome-wide,
transcription-profiling analysis of C. elegans infected with C. albicans yeast showed that exposure to C. albicans stimulated a
rapid host response involving 313 genes (124 upregulated and 189 downregulated,
,
1.6% of the genome) many of which
encode antimicrobial, secreted or detoxification proteins. Interestingly, the host genes affected by C. albicans exposure
overlapped only to a small extent with the distinct transcriptional responses to the pathogenic bacteria Pseudomonas
aeruginosa or Staphylococcus aureus, indicating that there is a high degree of immune specificity toward different bacterial
species and C. albicans. Furthermore, genes induced by P. aeruginosa and S. aureus were strongly over-represented among
the genes downregulated during C. albicans infection, suggesting that in response to fungal pathogens, nematodes
selectively repress the transcription of antibacterial immune effectors. A similar phenomenon is well known in the plant
immune response, but has not been described previously in metazoans. Finally, 56% of the genes induced by live C. albicans
were also upregulated by heat-killed yeast. These data suggest that a large part of the transcriptional response to C. albicans
is mediated through ‘‘pattern recognition,’’ an ancient immune surveillance mechanism able to detect conserved microbial
molecules (so-called pathogen-associated molecular patterns or PAMPs). This study provides new information on the
evolution and regulation of the innate immune response to divergent pathogens and demonstrates that nematodes
selectively mount specific antifungal defenses at the expense of antibacterial responses.
Citation: Pukkila-Worley R, Ausubel FM, Mylonakis E (2011) Candida albicans Infection of Caenorhabditis elegans Induces Antifungal Immune Defenses. PLoS
Pathog 7(6): e1002074. doi:10.1371/journal.ppat.1002074
Editor: Stuart M. Levitz, University of Massachusetts Medical School, United States of America
Received October 27, 2010; Accepted April 6, 2011; Published June 23, 2011
Copyright:
2011 Pukkila-Worley et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: This study was supported by the Irvington Institute Fellowship Program of the Cancer Research Institute (to RPW) and by the following grants from the
National Institutes of Health: K08 award AI081747 (to RPW), R01 award AI075286 (to EM), R21 award AI079569 (to EM), P01 award AI044220 (to FMA) and R01
award AI064332 (to FMA). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing Interests: RPW has served as a consultant for Optimer Pharmaceuticals, Inc. EM has received research support from and served on an advisory
board for Astellas Pharamceuticals, Inc. The authors report no other potential conflicts of interest.
* E-mail: ausubel@molbio.mgh.harvard.edu (FMA); emylonakis@partners.org (EM)
.
These authors contributed equally to this work.
Introduction
organism through the blood stream [9–11]. Hyphae, by contrast,
are important for host invasion and tissue destruction [1,8,11,12].
The factors that influence these diverse growth patterns during
infection are poorly understood, but it is clear that innate immune
mechanisms in mammalian epithelial cells normally prevent C.
albicans from becoming a pathogen [13–15]. Recently, genetic
analyses of two human families whose members suffered from
recurrent or chronic candidiasis on mucosal surfaces identified
causative mutations in the innate immune regulators dectin-1 [16]
and CARD9 [17]. Dectin-1 is a pattern-recognition receptor
important for macrophage phagocytosis of fungi. Interestingly, this
protein interacts differently with the C. albicans growth forms. Cell
wall components exposed in the bud scar of C. albicans yeast (so-
called pathogen-associated molecular patterns or PAMPs) potently
stimulate dectin-1, but hyphae are relatively shielded from innate
immune detection, which likely contributes to the ability of C.
albicans to establish infection [13,15,18]. Furthermore, a recent
study found that the p38 MAP kinase, a central regulator of
Candida albicans is a remarkably successful and versatile human
pathogen that is found on the skin and mucosal surfaces of virtually all
humans. Under most circumstances, C. albicans is a harmless
commensal [1]. However, this opportunist can invade host tissues
and cause life-threatening infections when the immune system is
weakened (e.g. from critical illness) and competing bacterial flora are
eliminated (e.g. from broad-spectrum antibiotic use). Accordingly,
invasive candidiasis is particularly common in intensive care units
where mortality rates reach 45–49% [2–4]. Antecedent colonization
of mucosal surfaces with C. albicans canalsoleadtodeblitating
superficial infections in otherwise normal hosts. Approximately 75%
of all women, for example, will have one episode of Candida vaginitis
in their lifetime, with half having at least one recurrence [5].
C. albicans can grow vegetatively as yeast or hyphae, and each
form contributes to pathogenesis [6–8]. C. albicans yeast cells
colonize mucosal surfaces and facilitate dissemination of the
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Antifungal Immunity in C. elegans
Author Summary
host C. elegans. In a previous study, we found that C. albicans hyphae
can kill C. elegans in a manner that models key aspects of
mammalian pathogenesis [20,33]. In that assay, yeast cells were
ingested by nematodes on solid medium and, after transfer to
liquid medium, worms died with true hyphae piercing through
their bodies. During these experiments, we noted that when
infected worms were maintained on solid media, rather than
transferred to liquid media, the C. albicans yeast form caused
pathogenic distention of the nematode intestine and premature
death of the worms. Thus, we hypothesized that C. albicans yeast,
the form commonly found in the mammalian intestine [13,15,18],
also contain virulence determinants that allow infection of
C. elegans. We therefore developed an assay that is conducted
exclusively on solid media and allows the direct study of yeast-
mediated pathogenesis of the nematode. As shown in Figure 1, the
yeast form of the C. albicans laboratory reference strain DAY185
infected and killed C. elegans. Heat-killed C. albicans yeast cells were
not pathogenic to the nematode (Figure 1A) and caused less
distention of the nematode intestine compared to that seen
following exposure to live C. albicans (Figure 1B). We found that the
C. albicans clinical isolate SC5314 was also able to establish a lethal
infection in nematodes (Figure 2). Furthermore, the C. albicans
efg1D/efg1D cph1D/cph1D double mutant strain [8], which is
attenuated for virulence in mammals, was also unable to efficiently
kill C. elegans in this assay (Figure 2). Like its isogenic wild-type
parent strain, virulence-attenuated C. albicans yeast enter the
nematode intestine during the infection assay (data not shown),
suggesting that non-specific occlusion of the intestine with yeast is
not the mechanism of C. albicans-mediated worm killing. In
addition, we found that C. albicans killed sterile C. elegans fer-
15(b26);fem-1(hc17) animals (data not shown) and wild-type worms
in the presence of 5-fluoro-29-deoxyuridine (FUDR), a compound
that prevents progeny from hatching (Figure 1A). These results
suggest that killing of nematodes by C. albicans yeast in the C. elegans
model involves virulence determinants intrinsic to live fungi and
not a ‘‘matricidal effect’’ from premature hatching of embryos
inside animals, a previously described, non-specific consequence of
pathogen stress in wild-type worms [26,31,32,34]. In summary,
these data demonstrate that C. albicans yeast are pathogenic to the
nematode and establish a second assay, which together with the
liquid-media system [33], permit separate in vivo analyses of C.
albicans growth states.
Despite being a part of the normal flora of healthy individuals,
Candida albicans is the most common fungal pathogen of
humans and can cause infections that are associated with
staggeringly high mortality rates. Here we devise a model for
the study of the host immune response to C. albicans infection
using the nematode C. elegans. We found that infection with
the yeast form of C. albicans induces rapid and robust
transcriptional changes in C. elegans.Analysesofthese
differentially regulated genes indicate that the nematode
mounts antifungal defenses that are remarkably distinct from
the host responses to pathogenic bacteria and that the
nematode recognizes components possessed by heat-killed C.
albicans to initiate this response. Interestingly, during infection
with a pathogenic fungus, the nematode downregulates
antibacterial immune response genes, which may reflect an
evolutionary tradeoff between bacterial and fungal defense.
mammalian immunity, receives biphasic inputs from C. albicans
that are dependent on the morphologic form of the organism and
the local fungal burden [14]. These data suggest that the interplay
between C. albicans and the mammalian innate immune system
dictate the virulence potential of this specialized pathogen, yet
relatively little is known about the molecular mechanisms
underlying these interactions.
One approach to study evolutionarily conserved aspects of
epithelial innate immunity and microbial virulence uses the
invertebrate host Caenorhabditis elegans [19,20]. In nature, nema-
todes encounter numerous threats from ingested pathogens, which
have provided a strong selection pressure to evolve and maintain a
sophisticated innate immune system in its intestinal epithelium
[21]. Coordination of these defenses involves several highly-
conserved elements that have mammalian orthologs [22–25].
Furthermore, C. elegans intestinal epithelial cells bear a striking
resemblance to human intestinal cells [26] and because the
nematode lacks both a circulatory system and cells dedicated to the
immune response, the intestinal epithelium constitutes the primary
line of defense for the nematode against ingested pathogens. Thus,
it is possible to conduct analyses of innate immune mechanisms in
a physiologically-relevant, genetically-tractable system.
Much of the characterization of nematode immunity has used
nosocomial bacterial pathogens [27–30], particularly Pseudomonas
aeruginosa [22,31,32], but to date, the immune response directed
toward a medically-important, fungal pathogen has not been
defined. Here, we extend our previously-validated system for the
study of hyphal-mediated C. albicans virulence in the nematode [33]
to examine C. albicans yeast. Our goal was to use studies of C. elegans-
C. albicans interactions to identify novel, conserved features of
metazoan innate immunity. We found that the responses to
bacterial and fungal pathogens are remarkably distinct. Many of
the immune response effectors that are upregulated by either P.
aeruginosa or S. aureus are downregulated by infection with C. albicans
yeast. We also found that slightly more than half of the immune
response genes activated by infection with live C. albicans are also
upregulated by heat-killed C. albicans. Our data indicate that the C.
elegans immune response to C. albicans most likely involves detection
of conserved surface-associated molecular pattern molecules, as well
as detection of C. albicans virulence-related factors.
C. albicans Infection Induces a Rapid Host Response that
Involves Antimicrobial, Secreted and Detoxification
Genes
Previous studies have shown that C. elegans mounts a rapid and
specific immune response toward pathogenic bacteria [32,35,36];
however, it is not known how the nematode defends itself against
an intestinal fungal pathogen. We therefore used transcriptome
profiles of nematodes during an infection with C. albicans yeast to
define the antifungal immune response genes in the nematode. We
compared gene expression of animals exposed to C. albicans for
four hours with control worms fed the non-pathogenic food
source, heat-killed E. coli OP50. The short exposure time
maximized the yield for transcriptional changes associated with
pathogen detection, rather than gene expression changes associ-
ated with intestinal damage [36]. It was necessary to use heat-
killed E. coli for these experiments because live E. coli were
previously shown to be pathogenic to the nematode on C. albicans
growth media (brain heart infusion agar) [37]. We found that C.
elegans coordinates a rapid and robust transcriptional response to C.
albicans that involves approximately 1.6% of the nematode genome
(Figure 3). 124 genes were upregulated two-fold or greater in
Results
The Yeast Form of C. albicans is Pathogenic to C. elegans
To examine interactions between C. albicans and the innate
immune system, we established a novel system using the model
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 Antifungal Immunity in C. elegans
Figure 1. C. albicansyeast can kill C. elegans. (A) Live C. albicans
(closed diamonds) were pathogenic to nematodes on solid media,
whereas heat-killed C. albicans (open circles) and E. coli (crosses) were
not (P
,
0.001). The graph presents the average of three plates per
strain, each with 30 to 40 animals per plate. Data are representative of
two biological replicates. (B) Images of C. elegans animals exposed to
heat-killed E. coli (HK E.c.), heat-killed C. albicans (HK C.a.) or live C.
albicans (live C.a.) for 16 hours at 25
u
C are shown. Images of the
proximal (left) and distal (right) intestine were obtained using Nomarski
optics. Both live and heat-killed C. albicans accumulated within the
intestine, but only live C. albicans caused marked distention of the
proximal intestine. Arrows point to the pharyngeal grinder and
arrowheads outline the lumen of the intestine. The scale bar represents
20
m
m.
doi:10.1371/journal.ppat.1002074.g001
Figure 2. A C.albicansdouble mutant strain that is attenuated
for pathogenicity in mammals is also unable to efficiently kill
C. elegans. The C. albicans efg1
D
/efg1
D
cph1
D
/cph1
D
double mutant
strain (efg1/cph1) exhibited a reduced ability to kill C. elegans compared
to its isogenic wild-type parent strain SC5314 (P
,
0.001). The graph
presents the average of three plates per strain, each with 30 to 40
animals per plate. Data are representative of two biological replicates.
doi:10.1371/journal.ppat.1002074.g002
the C. albicans-induced transcriptional changes observed in our
microarray analysis are not specific to a particular yeast strain.
Examination of the genes induced by C. albicans in the
microarray analysis reveals the footprint of an immune response
toward a pathogenic fungus (Table 1). C. albicans infection results
response to C. albicans compared to heat-killed E. coli and 189
genes were downregulated at least two-fold (P,0.01) (Figure 3A
and Table S1A). For technical confirmation of the microarray
experiment, we selected 11 genes that showed varying degrees of
differential regulation and tested their expression by quantitative
real-time polymerase chain reaction (qRT-PCR) under each
microarray condition (Figure 3B and Table S2). Plotting the fold
difference observed in the transcriptome profiles versus the value
obtained by qRT-PCR from the three biological replicates used
for the microarray analysis yielded an R
2
of 0.90 (Figure 3B),
which indicates tight correlation between these datasets and is a
result that compares favorably with similar analyses of other
microarray experiments [38]. We also tested three additional
biological replicates and found similar fold changes between the
microarray and qRT-PCR analyses in 10 of the 11 genes (Table
S2), a correlation rate that is consistent with other microarray
analyses of pathogen response genes in the nematode [34]. As a
third means to confirm the results of our microarray, we compared
the expression of 4 upregulated and 4 downregulated genes in
wild-type C. elegans animals infected with a different C. albicans
strain than used for the microarray analysis. We exposed animals
to the C. albicans clinical isolate SC5314, a strain that is also
virulent toward C. elegans (Figure 2), and found similar transcrip-
tional changes between C. albicans SC5314 and DAY185-exposed
animals for all 8 genes tested (Table S2). These data suggest that
Figure 3. Infection with C. albicansyeast induces a rapid host
response. (A) C. elegans genes that were differentially regulated in C.
albicans-exposed versus heat-killed E. coli-exposed young adult animals
at 4 hours after infection are depicted on a genome-wide intensity plot
of 22,548 sequences. Genes colored red were upregulated by C.
albicans (P
,
0.01), those colored green were downregulated (P
,
0.01)
and those colored blue were unchanged. Diagonal lines represent 2-
fold change and the numbers of genes differentially regulated greater
than 2-fold are indicated (P
,
0.01)(124 genes were upregulated and 189
genes were downregulated). (B) qRT-PCR was used to confirm the
results of the microarray analysis. 11 genes with varying degrees of
differential regulation were selected and studied under each condition
in which they were differentially regulated in the microarray analysis
(see Table S2 for gene identities). Correlation of microarray and qRT-PCR
data was determined by plotting the average fold difference observed
in the microarray analysis (three biological replicates) versus the
average fold difference for the same gene obtained by qRT-PCR (three
biological replicates). Linear regression analysis revealed strong
correlation between the datasets (R
2
of 0.90).
doi:10.1371/journal.ppat.1002074.g003
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Antifungal Immunity in C. elegans
in the elaboration of at least seven putative antimicrobial peptides,
which are postulated to have antifungal activity in vivo. One of
these genes, abf-2, was previously shown to have in vitro activity
against the pathogenic fungus Candida krusei [39]. Three genes in
this group (fipr-22/23 and two caenacin genes, cnc-4 and cnc-7) are
antifungal immune effectors induced by the nematode following
exposure to Drechmeria coniospora, an environmental fungal
pathogen, which causes a localized infection of the nematode
cuticle [40,41]. fipr-22 and fipr-23 have nearly identical DNA
sequences and thus, it is not possible for a probe set to distinguish
between these genes. Two chitinase genes (cht-1 and T19H5.1)
were also strongly induced by C. albicans. These enzymes are
secreted by metazoans and are thought to defend against chitin-
containing microorganisms such as C. albicans and other
pathogenic fungi [42,43]. In addition, thn-1, a gene that is
postulated to have direct antimicrobial activity and is a homolog of
the thaumatin family of plant antifungals [35,44], was induced 2.5-
fold during infection with C. albicans.
Using gene expression analyses, we characterized further the
expression pattern of four putative antifungal immune effectors
upregulated during C. albicans infection (abf-2, fipr-22/23, cnc-4 and
cnc-7). We exposed wild-type nematodes to the C. albicans efg1D/
efg1D cph1D/cph1D double mutant, a strain that is attenuated for
virulence in C. elegans (Figure 2) and mammals [8], and found that
the induction of abf-2, fipr-22/23, cnc-4 and cnc-7 was reduced
compared to its isogenic parent strain C. albicans SC5314 (P,0.01
for fipr-22/23 and cnc-7, P = 0.06 for abf-2, P,0.025 for cnc-4)
(Figure 4). These data suggest that the nematode modulates the
expression levels of antifungal immune effectors in response to
some aspect of C. albicans virulence, although this yeast may be
recognized differently by the nematode innate immune system
owing to pleotropic effects of the genetic lesions in this mutant
strain. We also found that the induction levels of these four genes
appear to be dynamic during infection. Twelve hours after
exposure to C. albicans, the expression of abf-2 increases
significantly, fipr-22/23 is unchanged and cnc-4 and cnc-7 is
reduced (Figure S1).
Among the most highly upregulated C. albicans defense genes
(Table 1), we also identified a preponderance of genes encoding
secreted proteins, intestinally-expressed proteins and proteins that
may function as detoxifying enzymes. Similar types of genes are
induced following infection with pathogenic bacteria [32,34]. As
discussed in more detail below, we also found that some of the C.
albicans-induced genes were involved in the nematode transcrip-
tional response to bacterial pathogens (Table 1), suggesting that C.
albicans and pathogenic bacteria induce a set of common immune
response effectors. Although it is possible that the effects of
nematode starvation are also reflected in the transcription profiling
data as a potential consequence of C. albicans being comparatively
non-nutritious relative to heat-killed E. coli, this seems less likely
since zero of the eighteen previously-identified, fasting-affected
genes [45] were differentially expressed in the dataset. Taken
together, these data suggest that the microarray analysis captured
the early defense response mounted by C. elegans toward an
ingested fungal pathogen.
pathogens P. aeruginosa [47] and Yersinia pestis [29], and in the
hypodermis to defend against the fungus D. coniospora [46]. We
found that C. elegans pmk-1(km25) mutants were hypersusceptible to
infection with C. albicans yeast (Figure 5A) and that PMK-1 was
required for the basal and pathogen-induced expression of three
antifungal immune effectors (fipr-22/23, cnc-4 and cnc-7), but not
abf-2 (Figure 5B). The full spectrum of nematode sensitivity to C.
albicans was not mediated by the genetic control of any of these
four effectors because knockdown of each of these genes
individually by RNA interference did not result in hypersuscep-
tibility to fungal infection (data not shown). It is likely, however,
that there is functional redundancy among immune effectors in C.
elegans, as has been suggested previously [29,32,44,49,50]. That
PMK-1 mediates resistance to C. albicans provides another line of
evidence that yeast infection of the nematode stimulates host
immune defenses. Moreover, the PMK-1-independent genetic
regulation of the antifungal effector abf-2 suggests that other
pathways are also important in controlling the immune response
toward C. albicans.
The Host Response to C. albicans Involves Induction of
Specific Defenses and Common Immune Genes
To examine the specificity of the antifungal transcriptional
response, we compared C. albicans-affected genes with those
differentially regulated following infection with the bacterial
pathogens P. aeruginosa [32] and Staphylococcus aureus [34]
(P,0.01, .2-fold change) (Figure 6). The transcriptional responses
induced by fungi, Gram-negative bacteria and Gram-positive
bacteria overlapped only to a small extent and the majority of the
C. albicans-affected genes were not involved in the response to P.
aeruginosa or S. aureus (Figure 6, Table S3A). The C. albicans-specific
genes in this comparison included the putative antifungal peptides
abf-2, fipr-22/23, cnc-7, thn-1 and the chitinases (cht-1 and
T19H5.1). We observed an overlap of 32 induced and 22
repressed genes between the transcriptional responses to P.
aeruginosa and C. albicans (1.9 and 1.4 genes expected by chance
alone, respectively; P,1.0610
216
for both comparisons). Like-
wise, 22 upregulated and 25 downregulated genes were shared in
the responses to S. aureus and C. albicans (2.8 and 2.2 genes
expected by chance alone, respectively; P,1.0610
216
for both
comparisons). Interestingly, 12 genes were induced and 14 genes
were repressed by all three pathogens. Despite the fact that the C.
albicans-induced genes were determined using heat-killed E. coli as
the control and the genes induced by P. aeruginosa and S. aureus
were identified in separate studies that used live E. coli as the
control, we detected an overlap of comparable significance
between the transcriptional responses to these different organisms.
26% and 18% of C. albicans-induced genes were also upregulated
by P. aeruginosa and S. aureus, respectively (Figure 6). Likewise, 17%
of genes induced by P. aeruginosa four hours after infection were
also upregulated by S. aureus and 11% of S. aureus-upregulated
genes were induced by M. nematophilum [34]. Our data suggest that
the nematode is able to specifically recognize C. albicans infection
and mount a targeted response toward this fungus that involves
antifungal defenses and a limited number of common core
effectors.
The Conserved PMK-1/p38 MAP Kinase Mediates
Resistance to C. albicans Infection
Genetic, biochemical and molecular analyses have identified a
requirement for the PMK-1 mitogen-activated protein (MAP)
kinase, orthologous to the mammalian p38 MAPK, in C. elegans
immunity [22,29,46–48]. PMK-1 is a central regulator of
nematode defenses [32] that acts cell autonomously both in the
intestine to control resistance toward the Gram-negative bacterial
Both Heat-Killed and Live C. albicans Yeast Are
Immunogenic to the Nematode
Components of the C. albicans cell wall, often referred to as
PAMPs, are recognized by mammalian neutrophils, monocytes
and macrophages [13,15,51]. In this study, we found that heat-
killed C. albicans yeast accumulate within the C. elegans intestine
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Antifungal Immunity in C. elegans
Table 1. The C. elegans transcriptional response to C. albicans infection involves antimicrobial, detoxification and other
pathogen-response genes.
Sequence
name
Gene name Sequence description
Fold
Change Pvalue
Induced by
heat-killed
C.albicans
Presumptive
function
Signal
sequence
[85]
Gut
Expression
F44E5.4,
F44E5.5
Hsp70 family of heat shock
proteins
14.0
0.0001
-
Pathogen response
[86–88]
-
Yes [82]
F52F10.3
oac-31
Predicted acyltransferase
10.1
3.2
6
10
2
7
Yes
Detoxification [32,34,35,89] Yes
Yes [82]
M01H9.1
trx-3
Thioredoxin, nucleoredoxin
9.6
3.4
6
10
2
11
Yes
Detoxification [32,89]
-
Yes [81]
ZK550.2
Predicted transporter/
transmembrane protein
8.4
0.00006
Yes
-
Yes [81]
C37A5.2,
C37A5.4
fipr-22,
fipr-23
Presumptive antimicrobial
peptide
6.7
0.002
-
Antimicrobial [40]
Yes
Yes [82]
C50F2.10
abf-2
Antimicrobial peptide
5.9
4.2
6
10
2
14
Yes
Antimicrobial [39]
Yes
Yes [39]
T07G12.5
Xanthine/uracil/vitamin C
transporter, Permease
5.4
0.00008
Yes
Detoxification [32,89]
Yes
- [82]
C54F6.14
ftn-1
Ferritin heavy chain homolog
4.9
1.2
6
10
2
18
Yes
Stress response [90]
-
Yes [90]
T19H5.1
Chitinase
4.7
0.002
-
Antimicrobial [42,43]
Yes
C01G6.7
acs-7
Acyl-CoA synthetase
4.5
1.2
6
10
2
17
Yes
Pathogen response [32]
-
Yes [82]
Y60C6A.1
4.4
1.0
6
10
2
7
Yes
Pathogen response [32]
Yes
R09B5.9
cnc-4
Caenacin antimicrobial peptide 4.1
1.9
6
10
2
11
Yes
Antimicrobial [41]
Yes
Yes [82]
T09B9.2
Permease
4.1
0.01
-
Detoxification [34]
Yes
Y46H3A.4
Predicted lipase
4.0
9.6
6
10
2
6
Yes
Antimicrobial [34]
-
T21C9.8
Transthyretin-like family
4.0
0.001
Yes
Pathogen response [32]
Yes
T06D8.1
Domain of unknown function
3.9
5.6
6
10
2
24
Yes
Yes
Y38E10A.15 nspe-7
Nematode specific peptide family 3.6
0.002
-
Yes
F58E10.7
3.6
2.9
6
10
2
15
Yes
Yes
C25H3.10
Cyclin-like F-box domain
3.6
4.6
6
10
2
17
-
Pathogen response [32]
-
F35E12.5
CUB-like domain
3.5
4.9
6
10
2
10
Yes
Pathogen response
[29,32,35]
Yes
Yes [29]
C04F6.3
cht-1
Chitinase
3.4
1.5
6
10
2
12
Yes
Antimicrobial [42,43]
Yes
R05H10.1
3.3
2.6
6
10
2
6
-
-
Yes [82]
C04F5.7
ugt-63
UDP-glucuronosyl and
UDP-glucosyl transferase
3.2
0.005
-
Detoxification [32,89]
Yes
T16G1.4
Domain of unknown function
3.2
6.0
6
10
2
6
Yes
-
F58H1.7
Low density lipoprotein-receptor 3.1
0.001
-
Yes
C33D9.1
exc-5
Guanine nucleotide exchange
factor for cdc-42
3.1
0.007
Yes
-
F13E9.11
3.1
2.0
6
10
2
6
Yes
Pathogen response [32,35]
-
F49E11.10 scl-2
SCP/TAPS domain-containing
secretory protein
3.1
1.8
6
10
2
31
Yes
Pathogen response [32,35] Yes
Yes [82]
C04A11.3
gck-4
Ste20-like serine/threonine
protein kinase
3.0
0.0004
-
Pathogen response [91]
-
Yes [81]
F18C5.10
3.0
1.3
6
10
2
15
-
-
Y41D4B.16
Domain of unknown function
3.0
0.0001
Yes
Pathogen response [29,32] Yes
Y80D3A.7 ptr-22
Sterol sensing domain protein 3.0
0.00001
-
Yes
Y38E10A.16 nspe-5
3.0
0.01
-
Yes
Genes upregulated 3-fold or more by C. albicans compared to heat-killed E. coli are presented along with their associated P values. Genes that were also induced by
heat-killed C. albicans versus heat-killed E. coli (P
,
0.01) are indicated. The cited references were used to determine the presumptive function of the genes and whether
the gene is expressed in the gut. The presence of a signal sequence suggests that the gene product is secreted and was determined using SignalP 3.0 [85]. ‘‘-’’ means an
answer of ‘No’ and a blank cell in the table indicates that information was not available. The Affymetrix probes for F44E5.4/5 and C37A5.2/4 could not distinguish
between the individual genes owing to sequence similarity.
doi:10.1371/journal.ppat.1002074.t001
(Figure 1B) and therefore postulated that the nematode transcrip-
tional response to nonpathogenic, heat-killed fungi would reflect
stimulation of host pathways by immunogenic components of the
yeast cell wall. To explore the mechanisms of pathogen detection
in the nematode, we fed animals heat-killed C. albicans as an
additional condition in the transcriptome profiling experiment.
PLoS Pathogens | www.plospathogens.org
5
June 2011 | Volume 7 | Issue 6 | e1002074
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