Journal Article

Copper-Induced Proline Synthesis is Associated with Nitric Oxide Generation in <i>Chlamydomonas reinhardtii</i>

Li Ping Zhang, Surya Kant Mehta, Zhao Pu Liu and Zhi Min Yang

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 49, issue 3, pages 411-419
Published in print March 2008 | ISSN: 0032-0781
Published online March 2008 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcn017
Copper-Induced Proline Synthesis is Associated with Nitric Oxide Generation in Chlamydomonas reinhardtii

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Excess copper affects the growth and metabolism of plants and green algae. However, the physiological processes under Cu stress are largely unknown. In this study, we investigated Cu-induced nitric oxide (NO) generation and its relationship to proline synthesis in Chlamydomonas reinhardtii. The test alga accumulated a large amount of proline after exposure to relatively low Cu concentrations (2.5 and 5.0 μM Cu2+). A concomitant increase in the intracellular NO level was observed with increasing concentrations of Cu applied. Data analysis revealed that the endogenous NO generated was positively associated with the proline level in Cu-stressed algae. The involvement of NO in Cu-induced proline accumulation was confirmed by using an NO-specific donor, sodium nitroprusside (SNP), and an NO scavenger cPTIO [2-(4-carboxy-2-phenyl)-4,4,5,5-tetramethylinidazoline-1-oxyl-3-oxide]. Pre-treatment with 10 μM SNP increased the proline accumulation in Cu-treated cells by about 1.5-fold, while this effect could be blocked by addition of 10 μM cPTIO. We further investigated the effect of Cu and NO on the activity and transcript amount of Δ1-pyrroline-5-carboxylate synthetase (P5CS, EC 2.7.2.11), the key enzyme of proline biosynthesis, and observed that application of SNP was able to stimulate the P5CS activity and up-regulate the expression of P5CS in the Cu-treated algae. These results indicate that Cu-responsive proline synthesis is closely related to NO generation in C. reinhardtii, suggesting the regulatory function of NO in proline metabolism under heavy metal stress.

Keywords: Chlamydomonas reinhardtii; Copper; Nitric oxide; Proline

Journal Article.  5534 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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