Figure 2. Response to Heat Treatment in Buchnera-Ap lines, for Genes Typically Up-Regulated in Response to Heat.

(A) Gene expression changes in response to heat treatment (35 °C) as measured from a microarray experiment, including two control genes (argG and cysG) that did not show significant responses to heat treatment. Each bar represents the mean of technical and biological replicates of each line (four arrays/aphid line) ± standard error.

(B) Gene expression changes in response to heat (35 °C) as measured with RT-qPCR using several A. pisum lines containing Buchnera with either short or long ibpA promoter alleles. For the long allele, n = 4 (three lines), and for the short allele, n = 2 (two lines). Error bars indicate means ± standard errors.

(C) Effects of exposure to different temperatures on ibpA expression for three aphid lines bearing Buchnera with different ibpA promoter alleles. The two 5A lines differ only in the single-base deletion affecting the length of the ibpA spacer; whereas TUC matches 5A-long for the ibpA promoter sequence, but shows other differences from 5A lines throughout the Buchnera genome. Pairwise differences between the two 5A-derived lines are significant at every temperature, with the long allele always showing higher expression relative to a control gene (cysG). TUC has other sequence differences, and these appear to have minor effects on ibpA expression.