Expression of auxin and light-regulated arrestin-like proteins, G proteinsand nucleoside diphosphate kinase during induction and development of wheat somatic embryos

The modulation of three signal transduction elements: arrestin-like protein s, G proteins and NDPK was assessed during the induction of wheat (Triticum aestivum L.) somatic embryogenesis under different auxin (2,4-D) and light conditions. Immunological approaches using specific antibodies, kinase act ivity measurement and [alpha-P-32]-GTP-binding assay were performed. The in duction of embryogenic capacity by 2,4-D was characterised both by the incr eased expression of the classical 40-kDa arrestin-like form and by the appe arance of an additional arrestin-like protein of 29 kDa. The 40-kDa arresti n-like soluble form was unaffected by light stimuli. On the other hand, the 29-kDa arrestin-like form, specific of the embryogenic tissue culture, was found to be light regulated. From embryogenic cultures grown under light o r dark, different soluble G proteins from 22 to 48 kDa were detected by pro bing polyvinylidene fluoride (PVDF) blots with [alpha-P-32]-GTP. In additio n, in the microsomal fraction from light-grown cultures, a polypeptide of 2 0 kDa was heavily labelled. Under light conditions, cell proliferation indu ced by 2,4-D stimulated the appearance of a 32-kDa nucleoside diphosphate k inase (NDPK) form in addition to the classical 16-18-kDa protein, without a significant change in the NDPK activity. The modulated expression of plant arrestin-like proteins, G proteins and NDPK molecules in response to auxin and light support the view that they play key roles in signalling cascades participating in plant development. (C) 2000 Editions scientifiques et med icales Elsevier SAS.