G proteins consist of three subunits called alpha, beta and gamma.
Biochemical studies with inhibitors or toxins have suggested that the G proteins are also involved in signal transduction in plant cells. Two cDNA clones, LeArcA1 and LeArcA2, were obtained and sequenced. The LeArcA1 gene expressed in roots, stems, cotyledons, true leaves, flowers, and fruits. The expression of the LeArc2 gene also decreased in true leaves of tomato plants under the intensive light illumination. Systemin or methyl jasmonate has no effects on levels of mRNA for LeArcA1 and LeArcA2 genes.