In the filamentous cyanobacterium
Anabaena sp. strain, PCC 7120, heterocysts (which are nitrogen-fixing cells) are formed in the absence of combined nitrogen in the medium. Heterocysts are separated from one another by 10 to 15 vegetative cells along the filaments, which consist of
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In the filamentous cyanobacterium
Anabaena sp. strain, PCC 7120, heterocysts (which are nitrogen-fixing cells) are formed in the absence of combined nitrogen in the medium. Heterocysts are separated from one another by 10 to 15 vegetative cells along the filaments, which consist of a few hundred of cells.
hetR is necessary for heterocyst differentiation; and
patS and
hetN, expressed in heterocysts, play important roles in heterocyst pattern formation by laterally inhibiting the expression of
hetR in adjacent cells. The results of this study indicated that
pknH, which encodes a Ser/Thr kinase, was also involved in heterocyst pattern formation. In the
pknH mutant, the heterocyst pattern was normal within 24 h after nitrogen deprivation, but multiple contiguous heterocysts were formed from 24 to 48 h. A time-lapse analysis of reporter strains harboring a fusion between
gfp and the
hetR promoter indicated that
pknH was required to suppress
hetR expression in cells adjacent to the preexisting heterocysts. These results indicated that
pknH was necessary for the lateral inhibition of heterocyst differentiation to maintain the heterocyst pattern.
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