The disclosure generally relates to methods and materials for modulating cell productivity. In particular, the present disclosure provides polynucleotides and polypeptides that when overexpressed in microorganisms result in increased in productivity, such as increased biomass productivity. Also disclosed are methods of using the polynucleotides and polypeptides to modulate or increase productivity of host cells such as, for example, algal or heterokont cells. Genetically engineered host cells, such as algal and heterokont cells having increased biomass productivity and bioproducts derived from such host cells are also disclosed.