GTPgammaS antagonizes the mastoparan-induced in vitro activity of PIP-phospholipase C from symbiotic root nodules of Phaseolus vulgaris.
Phospholipase C (PLC) has been suggested to have a role in signal perception by Nod factors (NFs) in legume root hair cells. For instance, mastoparan, a well-described agonist of heterotrimeric G protein, induces nodulin expression after NFs treatment or Rhizobium inoculation. Furthermore, it has been recently demonstrated that mastoparan also mimics calcium oscillations induced by NFs, suggesting that PLC could play a key role during the nodulation process. In this study, we elucidate a biochemical relationship between PLC and heterotrimeric G proteins during NFs signaling in legumes. In particular, the effect of NFs on in vitro PLC activity from nodule membrane fractions in the presence of guanosine 5'-[gamma-thio]triphosphate (GTPgammaS) and mastoparan was assayed. Our results indicate that for phosphatidylinositol 4,5 bisphosphate (PIP(2))-PLC, there is a specific activity of 20-27 nmol mg(-1) min(-1) in membrane fractions of nodules 18-20 days after inoculation with Rhizobium tropici. Interestingly, in the presence of 5 microM mastoparan, PIP(2)-PLC activity was almost double the basal level. In contrast, PIP(2)-PLC activity was downregulated by 1-10 microM GTPgammaS. Also, PLC activity was decreased by up to 64% in the presence of increasing concentrations of NFs (10(-8) to 10(-5) M). NFs are critical signaling molecules in rhizobia/legume symbiosis that can activate many of the plant's early responses during nodule development. Calcium spiking, kinases, PLC activity and possibly G proteins appear to be components downstream of the NFs perception pathway. Our results suggest the occurrence of a dual signaling pathway that could involve both G proteins and PLC in Phaseolus vulgaris during the development of root nodules.
De Los Santos-Briones
César
C
Centro de Investigación Científica de Yucatán, Mérida, México. sbriones@cicy.mx
Cárdenas
Luis
L
Estrada-Navarrete
Georgina
G
Santana
Olivia
O
Minero-García
Yereni
Y
Quinto
Carmen
C
Sánchez
Federico
F
Nissen
P
P
D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology*; D036341:Intercellular Signaling Peptides and Proteins; D008070:Lipopolysaccharides / Q000378:metabolism; D010455:Peptides / Q000494:pharmacology*; D027805:Phaseolus / Q000187:drug effects* / Q000378:metabolism; D054801:Phosphoinositide Phospholipase C / Q000378:metabolism*; D055170:Plant Root Nodulation; D018517:Plant Roots / Q000187:drug effects* / Q000378:metabolism / Q000382:microbiology; D012231:Rhizobium / Q000502:physiology; D013559:Symbiosis; D014862:Wasp Venoms / Q000494:pharmacology*
D036341:Intercellular Signaling Peptides and Proteins; D008070:Lipopolysaccharides; C092533:Nod factor, Rhizobium etli; D010455:Peptides; D014862:Wasp Venoms; D016244:Guanosine 5'-O-(3-Thiotriphosphate); C037500:mastoparan; D054801:Phosphoinositide Phospholipase C