The  -subunit of a heterotrimeric G-protein from tobacco, NtGP 1, functions in K+ channel regulation in mesophyll cells

• Published in: Journal of experimental botany Vol. 50; no. 330; pp. 53 - 61
• Main Authors: Saalbach, G., Natura, G., Lein, W., Buschmann, P., Dahse, I., Rohrbeck, M., Nagy, F.
• Format: Journal Article
• Language: English
• Published: Oxford Oxford Publishing Limited (England) 01.01.1999
• ISSN: 0022-0957; 1460-2431
• DOI: 10.1093/jxb/50.330.53

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 [alpha]-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. Keywords:G-protein, cloning, antisense, K<+< channel regulation, Nicotiana tabacum.