© 2008 The Author(s).
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RESEARCH PAPER |
Extracellular ATP-induced NO production and its dependence on membrane Ca2+ flux in Salvia miltiorrhiza hairy roots
Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong
* To whom correspondence should be addressed: E-mail: bcjywu{at}polyu.edu.hk
Extracellular ATP (eATP) is a novel signalling agent, and nitric oxide (NO) is a well-established signal molecule with diverse functions in plant growth and development. This study characterizes NO production induced by exogenous ATP and examines its relationship with other important signalling agents, Ca2+ and H2O2 in Salvia miltiorrhiza hairy root culture. Exogenous ATP was applied at 10–500 µM to the hairy root cultures and stimulated NO production was detectable within 30 min. The NO level increased with ATP dose from 10–100 µM but decreased from 100–200 µM or higher. The ATP-induced NO production was mimicked by a non-hydrolysable ATP analogue ATP
S, but only weakly by ADP, AMP or adenosine. The ATP-induced NO production was blocked by Ca2+ antagonists, but not affected by a protein kinase inhibitor. ATP also induced H2O2 production, which was dependent on both Ca2+ and protein kinases, and also on NO biosynthesis. On the other hand, ATP induced a rapid increase in the intracellular Ca2+ level, which was dependent on NO but not H2O2. The results suggest that NO is implicated in ATP-induced responses and signal transduction in plant cells, and ATP signalling is closely related to Ca2+ and ROS signalling.
Key words: Ca2+, extracellular ATP, hairy roots, nitric oxide, reactive oxygen species, Salvia miltiorrhiza
Received 29 July 2008; Revised 2 September 2008 Accepted 3 September 2008
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