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Quantitative genetic analysis of life-history traits of Caenorhabditis elegans in stressful environments.

Harvey SC, Shorto A, Viney ME - BMC Evol. Biol. (2008)

Bottom Line: We found that lines of C. elegans vary in their phenotypic plasticity of dauer larva development, i.e. there is variation in the likelihood of developing into a dauer larva for the same environmental change.This chromosome II QTL controlling dauer larva development does not encompass any loci previously identified to control dauer larva development.Together the phenotypic and genotypic data suggest that these two major life-history traits are co-ordinated responses to environmental stress and that they are, at least in part, controlled by the same genomic regions.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Biological Sciences, University of Bristol, Woodland Road, Bristol, BS8 1UG, UK. Simon.Harvey@bristol.ac.uk

ABSTRACT

Background: Organisms live in environments that vary. For life-history traits that vary across environments, fitness will be maximised when the phenotype is appropriately matched to the environmental conditions. For the free-living nematode Caenorhabditis elegans, we have investigated how two major life-history traits, (i) the development of environmentally resistant dauer larvae and (ii) reproduction, respond to environmental stress (high population density and low food availability), and how these traits vary between lines and the genetic basis of this variation.

Results: We found that lines of C. elegans vary in their phenotypic plasticity of dauer larva development, i.e. there is variation in the likelihood of developing into a dauer larva for the same environmental change. There was also variation in how lifetime fecundity and the rate of reproduction changed under conditions of environmental stress. These traits were related, such that lines that are highly plastic for dauer larva development also maintain a high population growth rate when stressed. We identified quantitative trait loci (QTL) on two chromosomes that control the dauer larva development and population size phenotypes. The QTLs affecting the dauer larva development and population size phenotypes on chromosome II are closely linked, but are genetically separable. This chromosome II QTL controlling dauer larva development does not encompass any loci previously identified to control dauer larva development. This chromosome II region contains many predicted 7-transmembrane receptors. Such proteins are often involved in information transduction, which is clearly relevant to the control of dauer larva development.

Conclusion: C. elegans alters both its larval development and adult reproductive strategy in response to environmental stress. Together the phenotypic and genotypic data suggest that these two major life-history traits are co-ordinated responses to environmental stress and that they are, at least in part, controlled by the same genomic regions.

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C. elegans varies in its population growth rate. (A) The population size on days 5, 7 and 9 of 45 RILs and (B) this for six RILs and N2 (-■-) and DR1350 (-□-) in one representative assay.
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Figure 2: C. elegans varies in its population growth rate. (A) The population size on days 5, 7 and 9 of 45 RILs and (B) this for six RILs and N2 (-■-) and DR1350 (-□-) in one representative assay.

Mentions: We wished to determine how C. elegans varied for another important life-history trait, namely adult reproduction. To do this we determined the population size of 45 RILs as they grew. This showed that the population sizes of the lines increased over time, but that the rate of this increase differed between the lines (Figure 2A; for clarity these data from one representative assay are shown in Figure 2B). There were significant differences between the population sizes of the lines and in how they grew over time (TIME: F2,1039 = 23431.01, p = 0.048; LINE [ASSAY]: F37,1039 = 9.98, p < 0.001; TIME*LINE [ASSAY]: F74,1039 = 4.14, p < 0.001). There were also significant differences between the assays, and in how the populations grew between assays (ASSAY: F7,1039 = 130.84, p < 0.001; TIME*ASSAY: F14,1039 = 102.49, p < 0.001). Hence, the RILs vary in their population sizes and in how the populations grew over time. At the start of these assays (day 5) there are no limitations to population growth; as the size of the population increases (day 7), food conditions become limiting and by day 9, the food source is exhausted. We therefore posited that the variation between the RILs was due to both differences in the reproductive capacity of the lines (the effect of LINE), possibly manifest either by variation in their lifetime fecundities or their temporal schedule of reproduction, and by differences in how the reproductive capacity of the lines altered in response to density (the effect of TIME*LINE [ASSAY]). These possible explanations were investigated further.


Quantitative genetic analysis of life-history traits of Caenorhabditis elegans in stressful environments.

Harvey SC, Shorto A, Viney ME - BMC Evol. Biol. (2008)

C. elegans varies in its population growth rate. (A) The population size on days 5, 7 and 9 of 45 RILs and (B) this for six RILs and N2 (-■-) and DR1350 (-□-) in one representative assay.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2267162&req=5

Figure 2: C. elegans varies in its population growth rate. (A) The population size on days 5, 7 and 9 of 45 RILs and (B) this for six RILs and N2 (-■-) and DR1350 (-□-) in one representative assay.
Mentions: We wished to determine how C. elegans varied for another important life-history trait, namely adult reproduction. To do this we determined the population size of 45 RILs as they grew. This showed that the population sizes of the lines increased over time, but that the rate of this increase differed between the lines (Figure 2A; for clarity these data from one representative assay are shown in Figure 2B). There were significant differences between the population sizes of the lines and in how they grew over time (TIME: F2,1039 = 23431.01, p = 0.048; LINE [ASSAY]: F37,1039 = 9.98, p < 0.001; TIME*LINE [ASSAY]: F74,1039 = 4.14, p < 0.001). There were also significant differences between the assays, and in how the populations grew between assays (ASSAY: F7,1039 = 130.84, p < 0.001; TIME*ASSAY: F14,1039 = 102.49, p < 0.001). Hence, the RILs vary in their population sizes and in how the populations grew over time. At the start of these assays (day 5) there are no limitations to population growth; as the size of the population increases (day 7), food conditions become limiting and by day 9, the food source is exhausted. We therefore posited that the variation between the RILs was due to both differences in the reproductive capacity of the lines (the effect of LINE), possibly manifest either by variation in their lifetime fecundities or their temporal schedule of reproduction, and by differences in how the reproductive capacity of the lines altered in response to density (the effect of TIME*LINE [ASSAY]). These possible explanations were investigated further.

Bottom Line: We found that lines of C. elegans vary in their phenotypic plasticity of dauer larva development, i.e. there is variation in the likelihood of developing into a dauer larva for the same environmental change.This chromosome II QTL controlling dauer larva development does not encompass any loci previously identified to control dauer larva development.Together the phenotypic and genotypic data suggest that these two major life-history traits are co-ordinated responses to environmental stress and that they are, at least in part, controlled by the same genomic regions.

View Article: PubMed Central - HTML - PubMed

Affiliation: School of Biological Sciences, University of Bristol, Woodland Road, Bristol, BS8 1UG, UK. Simon.Harvey@bristol.ac.uk

ABSTRACT

Background: Organisms live in environments that vary. For life-history traits that vary across environments, fitness will be maximised when the phenotype is appropriately matched to the environmental conditions. For the free-living nematode Caenorhabditis elegans, we have investigated how two major life-history traits, (i) the development of environmentally resistant dauer larvae and (ii) reproduction, respond to environmental stress (high population density and low food availability), and how these traits vary between lines and the genetic basis of this variation.

Results: We found that lines of C. elegans vary in their phenotypic plasticity of dauer larva development, i.e. there is variation in the likelihood of developing into a dauer larva for the same environmental change. There was also variation in how lifetime fecundity and the rate of reproduction changed under conditions of environmental stress. These traits were related, such that lines that are highly plastic for dauer larva development also maintain a high population growth rate when stressed. We identified quantitative trait loci (QTL) on two chromosomes that control the dauer larva development and population size phenotypes. The QTLs affecting the dauer larva development and population size phenotypes on chromosome II are closely linked, but are genetically separable. This chromosome II QTL controlling dauer larva development does not encompass any loci previously identified to control dauer larva development. This chromosome II region contains many predicted 7-transmembrane receptors. Such proteins are often involved in information transduction, which is clearly relevant to the control of dauer larva development.

Conclusion: C. elegans alters both its larval development and adult reproductive strategy in response to environmental stress. Together the phenotypic and genotypic data suggest that these two major life-history traits are co-ordinated responses to environmental stress and that they are, at least in part, controlled by the same genomic regions.

Show MeSH
Related in: MedlinePlus