results in developmental progression of heterocyst heterocyst development heterocyst differentiation The cellular developmental process by which a cell becomes a heterocyst, a cell that carries out nitrogen fixation. This process involves changes to the cell wall, expression of nitrogenase and other proteins involved in nitrogen fixation, and degradation of photosystem II, which produces oxygen. This process is known to occur in some cyanobacteria. GO:0043158 heterocyst formation biological_process heterocyst cell differentiation cellular developmental process