ANALYSIS OF GAMETOPHYTIC DEVELOPMENT IN THE MOSS, PHYSCOMITRELLA-PATENS, USING AUXIN AND CYTOKININ RESISTANT MUTANTS

Mutants altered in their response to auxins and cytokinins were isolated in the moss P. patens either by screening clones from mutagenized spores for growth on high concentrations of cytokinin or auxin, in which case mutants showing altered sensitivities can be recognized 3-4 wk later, or by non-selective isolation of morphologically abnormal mutants, some of which have altered sensitivities. Most of the mutants obtained selectively are also morphologically abnormal. The mutants are heterogeneous in their responses to auxin and cytokinin, and the behavior of some is consistent with their inability to synthesize auxin, while that of others may be due to their inability to synthesize cytokinin. Physiological analysis of the mutants has shown that both endogenous auxin and cytokinin are likely to play important and interdependent roles in several steps of gametophytic development. Although their morphological abnormalities lead to sterility, genetic analysis of some of the mutants has been possible by polyethyleneglycol induced protoplast fusion.