Protein content and electrophoretic profile of insect galls on susceptible and resistant host plants of Bauhinia brevipes Vogel (Fabaceae)

Gall induction, mediated by insect-herbivore chemical stimuli, is the result from anatomical and biochemical alterations in the host-plant tissues that provides shelter, food and defence against natural enemies and the harsh environment to the gall inducer. Schizomya macrocapillata Maia (Diptera, Cecidomyiidae) induces galls on Bauhinia brevipes Vogel (Fabaceae); the galls are spherical, with long reddish hairs that cover the adaxial wall surface of the gall, and a protuberance is observed on the abaxial leaf surface. Some plants are resistant to gall formation and, in many cases, this formation is inhibited by hypersensitive reaction. In the present work, samples from different parts of the non-galled and galled tissues from resistant and susceptible plants were carefully dissected. Indicating elevated metabolic activity, the protein concentration was 1.5-4.5-fold higher in the abaxial portion of the galls than in any other tissues, regardless of whether the galls were from resistant or susceptible plants. Different tissues from susceptible and resistant plants had distinct protein concentrations, and the fractionation of the proteins by SDS-PAGE and silver-staining showed shared and/or specific polypeptides. We hypothesise that specific proteins, possibly from distinct metabolic pathways, are involved in the physiological processes that determine whether the plant shows total and/or partial host resistance to the galling-insect attack.