Rice receptor for chitin oligosaccharide elicitor does not couple to heterotrimeric G-protein: Elicitor responses of suspension cultured rice cells from Daikoku dwarf (d1) mutants lacking a functional G-protein α-subunit

We present evidence that the rice receptor for N-acetylchitooligosaccharide elicitor does not couple to heterotrimeric G-protein (G-protein), one of the most important signal transducers from the cell surface to down-stream effectors in various cellular responses of many organisms. Using mutant rice cells lacking functional G-protein α-subunit, cellular responses of suspension-cultured rice cells derived from Daikoku dwarf (d1) mutants that were shown to contain mutations in the coding region of the G-protein α-subunit (Fujisawa et al. 1999) to N-acetylchitooligosaccharide (oligochitin) elicitor were compared with those of the corresponding parent cell lines. All the elicitor-induced cellular responses, such as medium alkalinization, generation of reactive oxygen species, expression of early responsive genes, PAL and PR genes, and production of phytoalexin, were basically identical in the mutant and wild type cell lines. Considering the reported presence of a single copy gene for the G-protein α-subunit in many plant species including rice, these results strongly support the above conclusion.