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The impact of host plant on the abundance and function of symbiotic bacteria in an aphid

T. L. Wilkinson^*,, D. Adams, L. B. Minto and A. E. Douglas

Department of Biology, University of York, York, YO10 5YW, UK
^* Present address: School of Biological Sciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
Present address: Insight Medical, 8 Hayne Street, London, EC1A 9RE, UK

View larger version (18K): [in a new window]   Fig. 1. The mass of 9-day-old larvae of A. fabae reared for 7 days on the three test plant species. Values are means ± S.E.M. (N=10). Values with different letters are significantly different (P>0.05) by Tukey’s test. ANOVA: for plant species: F2,54=17.37, P<0.001; for symbiosis: F1,54=77.03, P<0.001; for interaction: F2,54=4.11, 0.05>P>0.01.

View larger version (31K): [in a new window]   Fig. 2. The density of Buchnera and secondary symbionts in symbiotic aphids. Data were tested for significance by ANOVA (on logarithmic-transformed data): plant species, F2,78=51.52, P<0.001; tissue (total tissues versus embryos), F1,78=238.67, P<0.001; bacterial type (Buchnera versus secondary symbionts) F1,78=1298.5, P<0.001; plant species x tissue, F2,78=1.29, P>0.05; plant species x bacterial type, F2,78=23.62, P<0.001; bacterial type x tissue, F1,78=29.40, P<0.001; plant species x bacterial type x tissue, F2,78=2.95, P>0.05. Density is expressed per unit protein; the total aphid tissues comprised 43µgproteinmg-1freshmass (without significant variation among rearing plant species, P>0.05). Values are means ± S.E.M.

View larger version (28K): [in a new window]   Fig. 3. Incorporation of [U-14C]glutamic acid into amino acids of the protein fraction of symbiotic aphids, expressed as a percentage of total incorporation. ala, alanine; asx, aspartic acid + asparagine; glx, glutamic acid + glutamine; ile, isoleucine; thr, threonine. The F values for ANOVA tests for each amino acid after arcsine-square root transformation are shown. The critical value for significance of the ANOVA tests after Bonferroni correction for 5 tests is P=0.01; *significantly different value. Mean values with different letters are significantly different (P>0.01) by Tukey’s test.

View larger version (32K): [in a new window]   Fig. 4. Amino acid composition of phloem exudates of test plants. (A) percentage composition; values are means ± S.E.M. (N=10). (B) Principal components analysis of the percentage composition data. A, alanine; D, aspartic acid; E, glutamic acid; F, phenylalanine; G, glycine; H, histidine; I, isoleucine; K, lysine; L, leucine; M, methionine; N, asparagine; Q, glutamine; R, arginine; S, serine; T, threonine; V, valine; W, tryptophan; Y, tyrosine.

View larger version (14K): [in a new window]   Fig. 5. Amino acid composition of the free amino acid fraction in symbiotic aphids (closed bars) and aposymbiotic aphids (open bars). ala/tyr, alanine + tyrosine; arg/gly, arginine + glycine; asx, aspartic acid + asparagine; glx, glutamic acid + glutamine; his/ser, histidine + serine; ile, isoleucine; leu, leucine; lys, lysine; met/trp, methionine + tryptophan; phe, phenylalanine; thr, threonine; val, valine. Values are means ± S.E.M. (N=8).