NITRIC OXIDE AND PHOSPHOLIPID SIGNALING DURING STOMATAL CLOSURE

AYELEN DISTÉFANO; DENISE SCUFFI; CARLOS GARCIA-MATA; LORENZO LAMATTINA; ANA MARÍA LAXALT

Mar del Plata, Buenos Aires

Congreso; XXIX Reunión Argentina de Fisiología Vegetal; 2012

Sociedad Argentina de Fisiología Vegetal

Plants regulate gas exchange through stomata, which are pores located in the epidermis of the aerial part of the plant. Under drought stress, the hormone abscisic acid (ABA) promotes stomatal closing reducing transpiration and water loss. The signal transduction network triggered by ABA is one of the best-characterized signalling processes in guard cells. Among the second messengers that participate in ABA-induced stomatal closure are nitric oxide (NO), H2O2 and phospholipase D (PLD)-derived phosphatidic acid (PA). NO is a key signalling molecule that promote stomatal closure and increase plant tolerance to drought stress. NO increases PLD activity that is required for NO-induced stomatal closure. Arabidopsis has 12 PLD genes grouped into six types, PLDα(3) , β(2), γ(3) , δ, ε and ζ(2), based on structural and biological properties. Only two AtPLDs isoenzymes, PLDα1 and PLDδ, have been related to drought and dehydration stress. Recent evidences indicate that PLDα1 is upstream of NO production. However, we showed that PLD activation is downstream NO. Thus we hypothesized that PLD could be activated by NO. PLDδ is activated in response to H2O2, dehydration, cold and salinity stress. It is associated with the plasma membrane and has been suggested to be the microtubule-binding PLD in Arabidopsis. PLDδ mRNA levels increases in response to severe dehydration, high salts concentration and in ABA-treated guard cells. PLDδ knock-out plants (pldδ) failed to close the stomata in response to NO. ABA signalling in guard cells involves H2O2 and NO production. pldδ guard cells produced similar NO and H2O2 levels as the wild type in response to ABA. However, ABA- or H2O2-induced stomatal closure was impaired in pldplants. Unexpectedly, pldδ plants were more tolerant to drought. These data indicates that PLDδ is downstream of NO and H2O2 in ABA-induced stomatal closure and participates in drought stress.