INVOLVEMENT OF G-PROTEINS IN CHITOSAN?INDUCED ANTHRAQUINONE SYNTHESIS IN Rubia tinctorum.

ANDREA VASCONSUELO; GABRIELA PICOTTO; ANA M. GIULETTI; RICARDO BOLAND

PHYSIOLOGIA PLANTARUM

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2006 p. 29 - 37

0031-9317

We have previously shown that chitosan stimulates anthraquinone synthesisin Rubia tinctorum L. cells through activation of the PLC/PKC, PI3K, MAPKand Ca2þ messenger systems. In view of this evidence, we have now investigatedwhether guanine nucleotide-binding G-proteins are part of the signaltransduction mechanism which mediates the elicitor action. The G-proteinagonists mastoparan, AlF4? and GTPyS increased anthraquinone levels to thesame extent as chitosan. No additive effects were observed when culturedR. tinctorum cells were treated with agonist and the elicitor together. Inagreement with these observations, the G-protein antagonists suramin andGDPbS abolished the increase in anthraquinone synthesis induced by chitosan.Furthermore, elicitation was not affected in the presence of pertussistoxin. Consistent with this result, when cell cultures were preincubated witha monoclonal anti-Gaq/11 antibody, the chitosan-dependent increase inanthraquinone levels was fully inhibited. Moreover, the presence of animmunoreactive protein of the expected size for Gaq/11 (42 kDa) wasobserved in R. tinctorum microsomal membranes by Western blot analysisusing the same antibody. These results indicate that chitosan stimulatesanthraquinone synthesis in R. tinctorum cells through a heterotrimericG-protein, most likely belonging to the Gaq family.