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JXB Advance Access published online on March 14, 2008
Journal of Experimental Botany, doi:10.1093/jxb/ern048
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© 2008 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. This paper is available online free of all access charges (see http://jxb.oxfordjournals.org/open_access.html for further details)

RESEARCH PAPER

Regulation of carotenoid biosynthetic genes expression and carotenoid accumulation in the green alga Haematococcus pluvialis under nutrient stress conditions

Raman Vidhyavathi, Lakshmanan Venkatachalam, Ravi Sarada* and Gokare Aswathanarayana Ravishankar

Plant Cell Biotechnology Department, Central Food Technological Research Institute, Mysore – 570 020, India

* To whom correspondence should be addressed. E-mail: sarada_ravi{at}yahoo.com

Haematococcus pluvialis, a green alga, accumulates carotenoids, predominantly astaxanthin, when exposed to stress conditions. In the present work, changes in the pigment profile and expression of carotenogenic genes under various nutrient stress conditions and their regulation were studied. Nutrient stress and higher light intensity in combination with NaCl/sodium acetate (SA) enhanced total carotenoid and total astaxanthin content to 32.0 and 24.5 mg g–1 of dry biomass, respectively. Expression of carotenogenic genes, phytoene synthase (PSY), phytoene desaturase (PDS), lycopene cyclase (LCY), β-carotene ketolase (BKT), and β-carotene hydroxylase (CHY) were up-regulated under all the stress conditions studied. However, the extent of expression of carotenogenic genes varied with stress conditions. Nutrient stress and high light intensity induced expression of astaxanthin biosynthetic genes, BKT and CHY, transiently. Enhanced expression of these genes was observed with SA and NaCl/SA, while expression was delayed with NaCl. The maximum content of astaxanthin recorded in cells grown in medium with SA and NaCl/SA correlated with the expression profile of the astaxanthin biosynthetic genes. Studies using various inhibitors indicated that general carotenogenesis and secondary carotenoid induction were regulated at both the transcriptional and the cytoplasmic translational levels. The induction of general carotenoid synthesis genes was independent of cytoplasmic protein synthesis while BKT gene expression was dependent on de novo protein synthesis.

Key words: Astaxanthin, carotenoid, Haematococcus pluvialis, NaCl, nutrient stress, sodium acetate

Received 11 December 2007; Revised 21 January 2008 Accepted 30 January 2008


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