CP (2001) Role for hetC in the transition to a nondividing state during heterocyst differentiation in Anabaena sp

Nitrogen-deprived filaments of wild-type or hetC Anabaena sp. produce respectively, at semiregular intervals, heterocysts and weakly fluorescent cells. Unlike heterocysts, the latter cells can divide and elongate, producing a pattern of spaced series of small cells. Because a hetR::gfp fusion is expressed most strongly in the small cells, we propose that these small cells represent a very early stage of heterocyst differentiation. hetC::gfp is expressed most strongly in proheterocysts and heterocysts. Cyanobacteria are prokaryotes that are capable of oxygen-producing photosynthesis. Some filamentous species, like Ana-baena spp., fix dinitrogen under aerobic conditions in special-ized cells called heterocysts. These specialized cells differentiate from vegetative cells in response to deprivation of fixed nitro-gen. In wild-type Anabaena sp. strain PCC 7120 and many other strains, single heterocysts differentiate at semiregular intervals along vegetative filaments, forming a spacing pattern (23). Heterocysts, in which synthesis of biliprotein-containing antennae stops, are much more weakly autofluorescent tha