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 respe ctively, 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 exp ressed most strongly in the small cells, we propose that these small cells represent a very early stage of heterocyst differentiation. hetC::gfp is ex pressed most strongly in proheterocysts and heterocysts.