Genetic control of morphogenesis in the multicellular alga Ulva mutabilis: Defect in cell wall production

Abstract

Distinct ultrastructural differences between the cell walls of the mutant lumpy (lu) and wild-type are demonstrated. The polyglucan fibrils in the wild-type wall appear straight and densely packed compared to the more uneven and loosely woven fibrils in the mutant wall. The mutant grows as an aggregate of loosely connected cells. The three cell types seen in the wild type do not differentiate, and consequently no blade and holdfast forms. It is suggested that the defect in the cell wall production takes away a necessary condition for normal morphogenesis. The lumpy mutant shows epistasis over two other chromosomal mutants, bu and Sl, described earlier to be morphogenic.