Heterocyst Morphogenesis and Gene Expression in Anabaena sp. PCC 7120

Abstract

Many multicellular cyanobacteria produce specialized nitrogen-fixing heterocysts. During diazotrophic growth of the model organism Anabaena (Nostoc) sp. strain PCC 7120, a regulated developmental pattern of single heterocysts separated by about 10 to 20 photosynthetic vegetative cells is maintained along filaments. Heterocyst structure and metabolic activity function to accommodate the oxygen-sensitive process of nitrogen fixation. This dissertation focuses on my research on heterocyst development, including morphogenesis, transport of molecules between cells in a filament, differential gene expression, and pattern formation. We using microarray experiments we found that conR (all0187) gene is necessary for normal septum-formation of vegetative cells, diazotrophic grow, and heterocyst morphogenesis. In our studies we characterized the expression of sigma factors genes in Anabaena PCC 7120 during heterocyst differentiation, and we found that the expression of sigC, sigG and sigE is localized primarily in heterocysts. Expression studies using sigE mutant showed that nifH is under the control of this specific sigma factor.