S. Orset et Aj. Young, Low-temperature-induced synthesis of alpha-carotene in the microalga Dunaliella salina (chlorophyta), J PHYCOLOGY, 35(3), 1999, pp. 520-527
The microalga Dunaliella salina (Teo.) is well known as an accumulator of b
eta-carotene (beta,beta-carotene) when subjected to growth-limiting conditi
ons (e.g. exposure to high irradiances). In addition, the carotenoid alpha-
carotene (beta,epsilon-carotene) may also be synthesized and subsequently a
ccumulated by this alga under specific growth conditions. The main factor i
n stimulating the synthesis of this carotene was determined to be exposure
to lower than optimum temperatures for algal growth. A 7.5-fold increase in
the levels of alpha-carotene was observed when the temperature was decreas
ed from 34 to 17 degrees C, whilst levels of beta-carotene were unaltered.
The accumulation of or-carotene was unaffected by irradiance, although its
isomeric composition was greatly altered by light levels, The proportion of
9-cis alpha-carotene increased from 15% to 45% of total alpha-carotene whe
n the irradiance was decreased from 260 to 50 mu mol.m(-2).s(-1). Exposure
to higher irradiances had little influence on the isomeric composition of t
his carotenoid. A reduction in growth temperature did not influence the iso
meric composition of alpha-carotene. Nutrient status (nitrogen and phosphat
e) had no effect on either the content or isomeric composition of alpha-car
otene accumulated by D. salina.