Abstract
Auxin is known to play a critical role in various aspects of development in plants. To better understand the mechanisms of these auxin responses in plants, we focused on this response in the liverwort M. polymorpha. Application of naphthaleneacetic acid (NAA), an artificial auxin, over 1 μM to gemma confers growth inhibition in M. polymorpha. From γ-ray irradiated spores grown on 10 μM NAA-containing media, we isolated 7 auxin-resistant mutants. Interestingly, these mutants showed abnormal development of gemma, but no obvious phenotype in thallus development from established meristems. Spores of female auxin-resistant mutants did not properly develop, but the male auxin-resistant mutant formed motile sperm and successfully crossed with a wild type female to form spores. We also investigated auxin distribution during gametophyte and sporophyte development using transgenic M. polymorpha expressing the GUS gene driven by a soybean auxin-inducible GH3 promoter. Based on these results, we will discuss the roles of auxin in the development of M. polymorpha.
