초록
<P>The isolation and characterization of the phytoene synthase gene from the green microalga <I>Chlorella zofingiensis</I> (<I>CzPSY</I>), involved in the first step of the carotenoids biosynthetic pathway, have been performed. <I>CzPSY</I> gene encodes a polypeptide of 420 amino acids. A single copy of <I>CzPSY</I> has been found in <I>C. zofingiensis</I> by Southern blot analysis. Heterologous genetic complementation in <I>Escherichia coli</I> showed the ability of the predicted protein to catalyze the condensation of two molecules of geranylgeranyl pyrophosphate (GGPP) to form phytoene. Phylogenetic analysis has shown that the deduced protein forms a cluster with the rest of the phytoene synthases (PSY) of the chlorophycean microalgae studied, being very closely related to PSY of plants. This new isolated gene has been adequately inserted in a vector and expressed in <I>Chlamydomonas reinhardtii</I>. The overexpression of <I>CzPSY</I> in <I>C. reinhardtii</I>, by nuclear transformation, has led to an increase in the corresponding <I>CzPSY</I> transcript level as well as in the content of the carotenoids violaxanthin and lutein which were 2.0- and 2.2-fold higher than in untransformed cells. This is an example of manipulation of the carotenogenic pathway in eukaryotic microalgae, which can open up the possibility of enhancing the productivity of commercial carotenoids by molecular engineering.</P>