[24] Methods for investigating photoregulated carotenogenesis

Publisher Summary This chapter focuses on the mechanism by which light regulates the de novo synthesis of carotenoids in the red yeast, Rhodotorula minuta . The biosynthesis of carotenoid pigments is photoregulated in a wide range of organisms, and this photoregulation has been studied by many workers as a typical example of a biosynthetic process photoregulated in vivo . In some nonphotosynthetic microorganisms, in which carotenogenesis in the dark is either nil or very slight, short exposure to light followed by a return to darkness can considerably stimulate carotenogenesis. To elucidate the biochemistry of photoregulated carotenogenesis, it is necessary to obtain extensive data on the relationship between carotenoid production and light, and it is preferable to analyze these data stoichiometrically. A convenient and accurate method for the determination of carotenoid content is required. The influence of oxygen on carotenoid production in R. minuta is described in the chapter. Pure nitrogen gas is passed through an aqueous suspension of cells for 1 hr before their exposure to light and during the illumination. When cells illuminated under such anaerobic conditions are incubated under aerobic conditions in the dark, they produce almost the same amount of carotenoid as those illuminated under aerobic conditions.