Evolution and genetics of root hair stripes in the root epidermis

Root hair pattern develops in a number of different ways in angiosperm. Cel ls in the epidermis of some species undergo asymmetric cell divisions to fo rm a smaller daughter cell from which a hair grows, and a larger cell that forms a non-hair epidermal cell. In other species any cell in the epidermis can form a root hair. Hair cells are arranged in files along the Arabidops is root, located in the gaps between underlying cortical cell files. Epider mal cells overlying a single cortical cell file develop as non-hair epiderm al cells. Genetic analysis has identified a transcription factor cascade re quired for the formation of this pattern. WEREWOLF (WER) and GLABRA2 (GL2) are required for the formation of non-hair epidermal cells while CAPRICE (C PC) is required for hair cell development. Recent analyses of the pattern o f epidermal cells among the angiosperms indicate that this striped pattern of cell organization evolved from non-striped ancestors independently in a number of diverse evolutionary lineages. The genetic basis for the evolutio n of epidermal pattern in angiosperms may now be examined.