Plant Physiol, February 2001, Vol. 125, pp. 810-817
Regulation of Two Carotenoid Biosynthesis Genes Coding for
Phytoene Synthase and Carotenoid Hydroxylase during Stress-Induced
Astaxanthin Formation in the Green Alga Haematococcus
pluvialis
Jens
Steinbrenner and
Hartmut
Linden*
Lehrstuhl für Physiologie und Biochemie der Pflanzen,
Universität Konstanz, D-78457 Konstanz, Germany
Astaxanthin is a high-value carotenoid used as a pigmentation
source in fish aquaculture. In addition, a beneficial role of astaxanthin as a food supplement for humans is becoming evident. The
unicellular green alga Haematococcus pluvialis seems to
be a suitable source for natural astaxanthin. Astaxanthin accumulation in H. pluvialis occurs in response to environmental stress
such as high light and salt stress. Here, the isolation of the H. pluvialis carotenoid biosynthesis gene phytoene synthase is
reported. Furthermore, the expression of phytoene synthase and
carotenoid hydroxylase, two key enzymes in astaxanthin biosynthesis,
was investigated at the transcriptional level. The application of
environmental stress resulted in increased steady-state mRNA levels of
both genes. High-light intensity led to a transient increase in
carotenoid hydroxylase mRNA followed by moderate astaxanthin
accumulation. In contrast, salt stress in combination with high light
resulted in a sustained increase in both transcripts. The addition of
compounds inducing reactive oxygen species did not influence transcript levels of phytoene synthase and carotenoid hydroxylase. The application of an inhibitor of photosynthesis, 3-(3,
4-dichlorophenyl)-1,1-dimethylurea, indicated that the light-induced
expression of these carotenoid biosynthesis genes may be under
photosynthetic control.
*
Corresponding author; e-mail:
hartmut.linden{at}uni-konstanz.de; fax 49-7531-883042.
© 2001 American Society of Plant Physiologists
