Cynipid galls: insect‐induced modifications of plant development create novel plant organs

ABSTRACT Cynipid gall formation is achieved by an insect–plant interaction whereby cynipid gallwasps redirect host‐plant development to form novel structures to protect and nourish the developing larvae. Work was carried out to investigate the molecular mechanisms involved in this interaction, and extend the understanding of plant tissue development. Cytological changes of the inner‐gall tissue throughout the development of several gall species was investigated and the developmental stages of gall formation defined, to reveal two different patterns of development followed by the galls tested. Fluorescent in situ hybridization demonstrated many of the inner‐gall cells to be polytenized. Comparisons between inner‐gall and non‐gall tissue protein signatures by Schönrogge et al. (Plant, Cell and Environment 23, 215–222, 2000) have demonstrated the variation between gall and non‐gall protein signatures, and identified a number of inner‐gall proteins. Further analysis of one of these inner‐gall proteins involved in lipid synthesis, putative biotin carboxyl carrier protein (BCCP), revealed differential expression throughout development, and showed this expression to be concentrated in the inner‐gall tissue in all the gall species tested.