Fig. 3.

Cell-cycle regulation during the process of multicellular trichome formation. In tomato and some other species producing multicellular trichomes, mitosis needs to be repressed and endoreduplication (E) needs to be activated during trichome cell fate determination, and thereafter the protrichome cells will continue several mitosis cycles, resulting in the formation of multicellular forms. Mitosis is inhibited during trichome development, leading to unicellular forms. There may be a similar regulatory model before trichome initiation both in unicellular and multicellular trichome formation, and the dimerization of HD-Zip proteins and B-type cyclins (CycB) must play important roles in these processes