Poster: Intracellular Signaling

Abs # 835: Nitric oxide mediates MAPK activation during the IAA- induced adventitious root formation

Presenter:	Pagnussat, Gabriela C, gpagnussat@yahoo.com
Authors	Pagnussat, Gabriela C (A)   Lombardo, Cristina  (A)   Lanteri, Luciana  (A)   Lamattina, Lorenzo  (A)
Affiliations:	(A): Instituto de Investigaciones Biológicas

Recently, it was demonstrated that nitric oxide (NO) is involved in the auxin response during the adventitious rooting process in cucumber (Pagnussat et al., 2002). However, the molecular events involved during the adventitious root development triggered by auxins and NO are still unknown. This report describes the involvement of a MAPK cascade in the formation of adventitious roots induced by IAA and NO. Cucumber explants were treated with the NO donor SNP or with SNP plus the NO-scavenger cPTIO. Protein extracts from these explants were assayed for protein kinase (PK) activity by using Myelin basic protein (MBP) as substrate in both in vitro and in-gel assays. The activation of a PK of ~48 kDa could be detected with a maximal activation after 3 days of treatment with SNP. In control explants, the PK activity was only weakly detected after 4 days of treatment. PK activity was also assayed in explants treated either with IAA or with IAA plus the NO-scavenger cPTIO. Again, the MBP-kinase activity of ~48 kDa was detected in extracts from IAA-treated explants, while no signal was observed in IAA-treated ones maintained in the presence of cPTIO. Both the inhibition of the PK activity by the MAPK cell-permeable inhibitor PD098059 and its regulatory properties strongly suggested that the MBP-activity detected in cucumber explants is a MAPK activity. Furthermore, when PD098059 was administered to explants treated with SNP or IAA, it produced a delay in root emergence and a significant reduction in adventitious root development. All together, our results suggest that a MAPK signaling cascade is activated during the adventitious rooting process induced by IAA in a NO-mediated pathway. Supported by ANPCyT, UNMdP, CONICET and Fundación Antorchas.