Abstract
Auxin is known to play a critical role in various development aspects in plants. To better understand the mechanisms of auxin responses in plants, we used the liverwort Marchantia polymorpha L., which is one of the basal land plants and has less complex developmental processes than angiosperms. Application of artificial auxin, naphthaleneacetic acid (NAA), at 1 μM to gemma resulted in rhizoid formation not only on the bottom side of thallus, but also on the top side. In contrast, auxin tranport inhibitor, 2,3,5-triiodobenzoic acid (TIBA), at 10 μM reversed the dorsiventral axis of thallus. These results suggest that auxin is involved in determination of the dorsiventral axis during thallus development. To visualize auxin response, the β-glucuronidase (GUS) was expressed under the control of the soybean auxin-inducible promoter, GH3, in M. polymorpha. Transgenic plants carrying GH3::GUS showed GUS activity in an NAA-dependent manner. Histochemical staining of GUS revealed that auxin responses are different among tissues and developmental stages in M. polymorpha.
