GTPγS antagonizes the mastoparan‐induced in vitro activity of PIP 2 ‐phospholipase C from symbiotic root nodules of Phaseolus vulgaris
2008; Wiley; Volume: 135; Issue: 3 Linguagem: Inglês
10.1111/j.1399-3054.2008.01184.x
ISSN1399-3054
AutoresCésar De los Santos-Briones, Luis Cárdenas, Georgina Estrada‐Navarrete, Olivia Santana, Yereni Minero‐García, Carmen Quinto, Federico Sánchez,
Tópico(s)Plant nutrient uptake and metabolism
ResumoPhospholipase 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′‐[γ‐thio]triphosphate (GTPγS) 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 μ M mastoparan, PIP 2 ‐PLC activity was almost double the basal level. In contrast, PIP 2 ‐PLC activity was downregulated by 1–10 μ M GTPγS. 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.
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