抄録
Carotenoids are tetraterpene pigments that are composed of carbon 40 (C40) skeletons, and de novo synthesized in photosynthetic eukaryotes (plants including algae) and some microorganisms. Land plants produce β-carotene, lutein, zeaxanthin, violaxanthin, and neoxanthin as main carotenoids. Several higher plants can accumulate astaxanthin, or capsanthin and capsorubin, which are carotenoids unique to plant species, in their appropriate organs. Some higher plants also accumulate lycopene, α-carotene, or β-cryptoxanthin, which is a biosynthetic intermediate. On the other hand, carotenogenic bacteria are known to produce a great diversity of carotenoids, e.g., C40 carotenoids such as zeaxanthin, astaxanthin, nostoxanthin, spheroidenone, myxoxanthophyll, and isorenieratene, in addition to C30 linear carotenoids. Such diversity of carotenoids is derived from an abundance of carotenoid biosynthesis genes. The carotenoid biosynthetic pathway has been well elucidated in higher plants at the gene level. Moreover, increasing information on microbial genome sequences provides us with tools to investigate evolution of carotenoid biosynthesis genes. In this review, we describe the carotenoid biosynthetic pathway in both plants and microorganisms, and relevant biosynthesis genes. In addition, we discuss the phylogenetic relationship and evolution of these genes. Comparative analysis suggests that gene duplication, gene transfer, and gene modification resulted in the diversity and species-specificity of the carotenoid biosynthesis genes. In the future, more knowledge of carotenoid biosynthesis genes of various organisms is likely to reveal a detailed pathway for carotenogenic gene evolution.
