Biochemical Responses of Rice Cells to Mastoparan 7, an Activator of Heterotrimeric G Proteins.

In order to estimate whether mastoparan 7 specifically activates plant heterotrimeric G proteins, comparisons were made between the responses of a rice normal cultivar and a rice dwarf mutant, Daikoku d1, which has a mutation in the gene of the α subunit of a heterotrimeric G protein, to mastoparan 7. First, we found that mastoparan 7 induced the activity of the α-amylase via the heterotrimeric G protein in rice embryo-less half seeds. This observation indicated that mastoparan 7 activated the G proteins in plant cells, as does it in mammalian cells. Second, mastoparan 7 seemed to cause damages in rice cells in a G protein-independent manner under some experimental conditions. We propose that mastoparan 7 should carefully be used for study on the plant G protein-mediated signaling pathways.