ABSTRACT
Heterotrimeric G proteins are an important component of signal transduction pathway in animals. Although these proteins have been described in plants, their exact function and action mode are not clearly defined. In order to analyze the relationship between these proteins and the transduction of light signals in spinach, we have isolated by 5' and 3' RACE-PCR a 1660bp cDNA clone called SOGA1. This codes for a 383aa protein, which reveals a very strong homology with other plant Galpha subunit sequences. Genomic analysis suggested that SOGA1 belonged to a small multiple gene family. Northern blots and in-situ hybridization analyses showed that SOGA1 transcripts accumulate in all organs tested with a specific high level associated with the apex, roots and hypocotyls. Finally, a time-course analysis performed on the green tissues showed that accumulation of SOGA1 transcripts follows a circadian rhythm. However, in-situ hybridization analysis of the apex suggested the opposite behavior, while no variation was observed in the hypocotyl.
Subject(s)
DNA, Complementary/genetics , Heterotrimeric GTP-Binding Proteins/genetics , Spinacia oleracea/genetics , Amino Acid Sequence , Base Sequence , Blotting, Northern , Blotting, Southern , Circadian Rhythm , Cloning, Molecular , DNA, Complementary/chemistry , DNA, Complementary/isolation & purification , DNA, Plant/genetics , Gene Expression Regulation, Developmental , Gene Expression Regulation, Plant , In Situ Hybridization , Light , Molecular Sequence Data , Photoperiod , Phylogeny , Plants/genetics , RNA, Plant/genetics , RNA, Plant/metabolism , RNA, Plant/radiation effects , Sequence Alignment , Sequence Analysis, DNA , Sequence Homology, Amino Acid , Spinacia oleracea/growth & development , Tissue Distribution , Transcription, Genetic/radiation effectsABSTRACT
A phage library of cDNA from Arabidopsis thaliana has been screened with oligodeoxyribonucleotides designed from regions of high homology found in tobacco osmotin and other osmotin-like proteins. One of the selected clones, Atosm34, presents a 734 bp open reading frame encoding a polypeptide of 244 amino acids, including the putative N-terminal signal and C-terminal propeptide sequences. Comparative alignment reveals extensive homologies to osmotin and the osmotin-like proteins found in Solanaceae, and also to a related polypeptide found in soybean. Genomic hybridization suggests that the cDNA obtained here corresponds to a single copy gene, and RNA blot analysis showed that the level of expression is highest in old leaves.
