hetn

HetN is a gene found in heterocyst-forming cyanobacteria, notably in genera such as Anabaena and Nostoc. It encodes a regulatory protein involved in the control of heterocyst differentiation, the process by which certain vegetative cells become nitrogen-fixing heterocysts.

HetN acts as a negative regulator of heterocyst formation, contributing to the characteristic periodic spacing of heterocysts along cyanobacterial filaments. The current view is that HetN participates in a feedback mechanism: once a heterocyst forms, HetN helps inhibit the formation of additional heterocysts in neighboring cells, thereby maintaining an even distribution. The protein is thought to act downstream of HetR, the master activator of differentiation, and may participate in a diffusible signaling process across intercellular connections, although the exact molecular details remain under investigation.

Genetic and evolutionary studies show HetN is conserved among many heterocyst-forming cyanobacteria and is often located in genomic regions containing other patterning genes. Experimental disruption of hetN leads to irregular heterocyst spacing and increased clustering of differentiated cells, while overexpression can reduce the overall number of heterocysts under nitrogen-starved conditions.

See also: HetR, heterocyst, cyanobacteria differentiation.