Calcium and calcium-dependent protein kinase activation are involved in nitric oxide-induced adventitious root formation in cucumber

LANTERI ML, PAGNUSSAT GC, LAMATTINA L

JOURNAL OF EXPERIMENTAL BOTANY

Oxford Journals

Lugar: Lancaster, UK; Año: 2006 vol. 57 p. 1341 - 1351

0022-0957

A few years ago it was demonstrated that nitric oxide (NO) and cGMP are involved in the auxin response during adventitious root (AR) formation in cucumber (Cucumis sativus). More recently, a mitogen-activated protein kinase cascade was shown to be induced by IAA in a NO-dependent but cGMP-independent pathway. In the present study, it was evaluated the involvement of Ca2+ and the regulation of Ca2+-dependent protein kinase (CDPK) activity during the IAA- and NO-induced AR formation in cucumber explants. It was also examined the effectiveness of several broad-spectrum Ca2+ channel inhibitors and Ca2+ chelators in affecting AR formation induced by IAA or NO. Results indicate that the explants response to IAA and NO depends on the availability of both intracellular and extracellular Ca2+ pools. Protein extracts from cucumber hypocotyls were assayed for CDPK activity by using histone IIIS or syntide 2 as substrates for in-gel or in vitro assays, respectively. The activity of a 50 kD CDPK was detected after the 1st day of either NO or IAA treatments and it extended up to the 3rd day of treatment. This CDPK activity was affected in both extracts from NO- and IAA-treated explants in the presence of the specific NO-scavenger cPTIO, suggesting that NO is required for its maximal and sustained activity. The in-gel and the in vitro CDPK activity, as well as the NO- or IAA-induced AR formation, were inhibited by calmodulin antagonists. Furthermore, the induction of CDPK activity by NO and IAA was shown to be reliant on the activity of the enzyme guanylate cyclase.