Nitric oxide mediates the indole acetic acid induction activation of a mitogen-activated protein kinase cascade involved in adventitious root development

PAGNUSSAT GC, LANTERI ML, LOMBARDO MC, LAMATTINA L

PLANT PHYSIOLOGY.

American Society of Plant Biologists

Lugar: Rockville, USA; Año: 2004 vol. 135 p. 279 - 286

0032-0889

Recently, it was demonstrated that nitric oxide (NO) and cGMP are involved in the auxin response during the adventitious rooting process in cucumber (Pagnussat et al., 2002; 2003). However, not much is known about the complex molecular network operating during the cell proliferation and morphogenesis triggered by auxins and NO in that process. Anatomical studies showed that formation of adventitious root primordia (RP) was clearly detected in IAA- and NO-treated cucumber explants, while neither cell proliferation nor differentiation into RP could be observed in control explants 3 days after primary root was removed. In order to go further with signal transduction mechanisms that operate during IAA- and NO-induced adventitious root formation (ARF), experiments were designed to test the involvement of a mitogen-activated protein kinase (MAPK) cascade in that process. Cucumber explants were treated with the NO-donor sodium nitroprusside (SNP) or with SNP plus the specific NO-scavenger cPTIO. Protein extracts from those 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 approximately 48 kDa could be detected 1 day after NO-treatment with a maximal activation after 3 days of treatment. In control explants, a PK activity was only detected after 4 days of treatment. The MBP-kinase activity was also detected in extracts from IAA-treated explants, while no signal was observed in IAA + cPTIO treatments. The PK activity could be inhibited by the cell-permeable MAPK kinase inhibitor PD098059, suggesting that the NO-dependent MBP-kinase activity is a MAPK. Furthermore, when PD098059 was administered to explants treated with SNP or IAA, it produced a delay in root emergence and a dose-dependent reduction in root number. Altogether, our results suggest that a MAPK signaling cascade is activated during the adventitious rooting process induced by IAA in a NO-mediated but cGMP-independent pathway. The activation of MAPKs is discussed in relation to the cell responses modulating mitotic process.