Species-Specific and Thermostable Proteins from Second-Stage Larvae ofGlobodera rostochiensisandG. pallida

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Abstract
Different electrophoretic techniques were applied to extracts of second-stage larvae of six Globodera rostochiensis and six G. pallida populations. Electrophoresis of native proteins clearly distinguished G. rostochiensis from G. pallida. Four major protein bands were specific for G. rostochiensis and five for G. pallida. However, repeated experiments gave large variations in intensities of most of the species-specific protein bands. The species-specific protien bands resolved with sodium dodecyl sulfate (SDS) electrophoresis were more reproducible. In contrast with other reports, no consistent intraspecific variation could be detected with one-dimensional electrophoresis. Several of the species-specific proteins resolved with SDS electrophoresis appeared to be thermostable and were partially purified. Characterization of the thermostable polypeptides by two-dimensional electrophoresis (20) resolved three polypeptides specific for G. rostochiensis, with isoelectric points (pI) and molecular masses of 20.6 kDa (pI 5.30), 20.8 kDa (pI 5.20), and 18.0 kDa (pI 6.00); these differed slightly from those specific for G. pallida, with pI and molecular masses of 21.0 kDa (pI 5.32), 20.5 kDa (pI 5.40), and 17.0 kDa (pI 5.80).