Distribution of male (blue bars) or female (red bars) lifespans among DGRP lines infected with Ma549 (A) or Pa14 (B).

<p>Lifespans were measured as the time required for half the flies to die (LT50).</p

The genetic basis for variation in resistance to infection in the <i>Drosophila melanogaster</i> genetic reference panel

<div><p>Individuals vary extensively in the way they respond to disease but the genetic basis of this variation is not fully understood. We found substantial individual variation in resistance and tolerance to the fungal pathogen <i>Metarhizium anisopliae</i> Ma549 using the <i>Drosophila melanogaster</i> Genetic Reference Panel (DGRP). In addition, we found that host defense to Ma549 was correlated with defense to the bacterium <i>Pseudomonas aeruginosa</i> Pa14, and several previously published DGRP phenotypes including oxidative stress sensitivity, starvation stress resistance, hemolymph glucose levels, and sleep indices. We identified polymorphisms associated with differences between lines in both their mean survival times and microenvironmental plasticity, suggesting that lines differ in their ability to adapt to variable pathogen exposures. The majority of polymorphisms increasing resistance to Ma549 were sex biased, located in non-coding regions, had moderately large effect and were rare, suggesting that there is a general cost to defense. Nevertheless, host defense was not negatively correlated with overall longevity and fecundity. In contrast to Ma549, minor alleles were concentrated in the most Pa14-susceptible as well as the most Pa14-resistant lines. A pathway based analysis revealed a network of Pa14 and Ma549-resistance genes that are functionally connected through processes that encompass phagocytosis and engulfment, cell mobility, intermediary metabolism, protein phosphorylation, axon guidance, response to DNA damage, and drug metabolism. Functional testing with insertional mutagenesis lines indicates that 12/13 candidate genes tested influence susceptibility to Ma549. Many candidate genes have homologs identified in studies of human disease, suggesting that genes affecting variation in susceptibility are conserved across species.</p></div

Time course of CFU production in male flies from DGRP lines.

<p>Flies were homogenized and plated at 12 h intervals post-infection until death. Ten lines are shown as representative examples. CFUs were averaged from ten individual flies per fly line per time point.</p

Correlation analyses of LT₅₀ values among the DGRP lines between male and female flies infected with Ma549 (A), and between male flies infected with Pa14 or Ma549 (B).

<p>Correlation analyses of LT₅₀ values among the DGRP lines between male and female flies infected with Ma549 (A), and between male flies infected with Pa14 or Ma549 (B).</p

Male mean survival times of DGRP lines and their standard deviations when treated with Ma549.

<p>Male mean survival times of DGRP lines and their standard deviations when treated with Ma549.</p

Cellular networks of candidate genes.

<p>Enriched cellular genetic pathway for candidate genes from all genome wide association analyses (squares), allowing one missing gene (white triangles) or compound (white circles). The border colors indicate the over-represented gene ontology categories (<i>P</i><0.005): axon guidance (red), translation initiation (orange), protein phosphorylation (dark green), cell migration (magenta), phagocytosis and engulfment (yellow), arginine and proline metabolism (dark blue), purine metabolism (light blue), response to DNA damage (light green), ether lipid metabolism (gray), glycerolipid metabolism (teal), P450 related drug metabolism (brown).</p

Growth of GFP-expressing Ma549 can be visualized in DGRP flies.

<p>DGRP fly lines RAL_439, RAL_321 and RAL_38 photographed at different time points post infection with Ma549-GFP. A) No visible growth of Ma549-GFP in a living RAL_439 fly’s abdomen, and there are very few pre-mortem fungal propagules in squashed RAL_439 flies (B-C). Ma549-GFP only proliferates in RAL_439 post mortem (D). In contrast, Ma549-GFP blastospores and short hyphal lengths are visible in the hemocoele from outside a still living RAL_321 fly’s abdomen (E), and in pre- and post-mortem squash preparations (F to I). Variation among individual flies in resistant line RAL_38 in number of Ma549-GFP propagules per fly 6 days’ post-infection (J-N). At death, Ma549-GFP blastospores and short hyphal lengths are found in hemocoele of all DGRP lines (D, H, I and N). The pictures are representative of the 10 flies per line per time point examined for the experiment. Bars in images represent 20 μm.</p

Correlations of LT50 values among the DGRP lines for <i>M</i>. <i>anisopliae</i> Ma549 and <i>P</i>. <i>aeriginosa</i> Pa14 (this study) with traits previously measured by other groups.

<p>Correlations of LT50 values among the DGRP lines for <i>M</i>. <i>anisopliae</i> Ma549 and <i>P</i>. <i>aeriginosa</i> Pa14 (this study) with traits previously measured by other groups.</p

LT₅₀ differences between male and female flies in DGRP lines infected by Ma549 and Pa14.

<p>LT₅₀ values for females were subtracted from those of males so negative values indicate lines where female flies are more resistant than males. Lines are ranked from most to least susceptible males.</p

Analysis of variance of survival time of flies treated with Ma549 and Pa14.

<p>Analysis of variance of survival time of flies treated with Ma549 and Pa14.</p