Effects of high temperature on Carotenoid Accumulation and Gene Expression in the Model Green Alga Chlamydomonas reinhardtii

Abstract

Carotenoids are yellow, orange, or red pigments found in photosynthetic organisms and also in certain bacteria and fungi. They play crucial roles as accessory pigments for photosynthesis and as antioxidants for reducing cellular damage from free radicals. Microalgae provide one of the best sources for natural carotenoids. Outdoor cultivation of microalgae could be influenced by temperature changes. An increase in temperature may affect carotenoid production and gene expression. However, the regulation of carotenoid accumulation in response to high temperature is still poorly understood. To investigate how an increase in temperature affects growth and carotenoid accumulation in microalgae, the responses of Chlamydomonas reinhardtii cells shifted from 25°C to 37°C were studied. Results showed that temperature increase led to elevated levels of chlorophylls and an increase in the maximum quantum efficiency of photosystem II. In addition, carotenoid accumulation was induced by high temperature in the presence of light. The expression of genes involved in early steps of the pathway was induced by temperature change, whereas the expression of genes in later steps was not. Results from this study could be used to improve algal growth and productivity through informed selection of an optimal growth condition and genetic engineering.