Heterotrimeric GTPases (G-proteins) are implicated in many cellular signalling processes. In plants, a function of a specific G-protein has only recently been characterized. A cDNA clone encoding a G-protein alpha-subunit was isolated from tobacco (Nicotiana tabacum L.), The deduced amino acid sequence of this alpha-subunit (NtGP alpha 1) has 91% homology to GP alpha 1 from Arabidopsis thaliana, Sequence comparisons with other plant G-proteins show that these two a-subunits belong to the only class of plant G-proteins known to date. The NtGP alpha 1 cDNA was placed under the control of the CaMV 35S promoter both in sense and antisense orientation. These constructs were stably transformed into tobacco plants. As shown by patch-clamp experiments, mesophyll protoplasts of transformed tobacco plants over-expressing NtGP alpha 1 sense or antisense RNA exhibited enhanced plasmalemma K+ conductances compared to the wild type. By contrast, mesophyll protoplasts of transformed tobacco plants expressing the cholera toxin A1-subunit, a G-protein activator, exhibited a reduced plasmalemma K+ conductance. These results indicate for the first time a role of a specific G-protein in the regulation of K+ channels.
|Number of pages||9|
|Journal||Journal of Experimental Botany|
|Publication status||Published - Jan 1999|