Differentiation of aphid clones by arbitrarily primed polymerase chain reaction (AP-PCR) DNA fingerprinting


  • This work is intended to develop a technique to analyse the population structure of aphids at a high resolution, particularly that of eusocial aphids which produce sterile soldier castes and that of gall-forming species in which interesting interclonal interactions have been identified. Takema Fukatsu, a graduate student of the University of Tokyo, is studying the evolution of endosymbiosis in aphids from morphological, histological and molecular biological points of view, and is now preparing a doctoral thesis along these lines. He is also interested in the biology of eusocial aphids. Professor Hajime Ishikawa is organizing a laboratory at the Zoological Institute, University of Tokyo, to investigate molecular mechanisms of intracellular symbiosis in aphids.

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Differentiation of aphid clones was attempted using AP-PCR which is a simple and rapid method to obtain DNA fingerprints of complex genomes. To establish optimal reaction conditions and examine reproducibility of the method, a laboratory-maintained clone of the pea aphid, Acyrthosiphon pisum, was used as test material. Under the reaction conditions employed, identical fingerprint patterns were obtained throughout a wide range of template DNA amount, from 5 to 800 ng, and irrespective of aphid instar. No changes in the patterns were seen throughout five parthenogenetic generations. When this method was applied to a wild population of the gall-forming aphid, Ceratovacuna nekoashi, five groups of insects originating from different galls formed on the same twig were successfully differentiated from one another by means of polymorphic fingerprint bands. In contrast, the fingerprints of the insects derived from the subgalls of the same gall were identical. These results indicated that in C. nekoashi: (i) members of a gall constitute a clonal population; (ii) a gall is founded by a single fundatrix; and (iii) intergall migration is absent or at least not frequent.