Photosynthesis and expression of circadium gene KaiC in synechococcus

Abstract

This paper provided some evidences that there was a relationship between photosynthesis and circadian gene expression in unicellular cyanobacterium Synechococcus elongates PCC 7942. The gene KaiC was cloned by PCR technique and sense-or antisense-vectors were constructed. The cyanobacterium was transformed with two vectors, and up-or down-regulated mutants of Synechococcus were identified. Their photosynthesis and respiration was measured using oxygen electrode with wild type and mutants transformed by pRL-489, pRL-sense-kaiC and pRL-antisense-kaiC. The data showed that net photosynthesis in all mutants was lower than that in wild type cells, and dark respiration in all mutants was higher than that in wild type cells. When Synechococcus cells were cultivated in the filtrate of Scenedesmus obliquus medium the growth of both up- and down-regulated mutants were inhibited more than that of wild type cells. These data demonstrated that the expression of circadian gene KaiC affected cyanobacterial fitness, and the possible mechanism may be related to their photosynthesis.