Abstract: VPC (vegetative phase change) of higher plants undergo two stages, juvenile and adult phase. VPC is one of the important physiological processes in plant development, which is related to circadian clock regulation. Unfortunately, circadian clock related genes regulation during this transition remains unknown. In this paper, we investigated characters of VPC in a mutant of circadian clock-related gene, GI (Gigantea). Results showed that the life span of gi was prolonged. Onset of abaxial trichomes of rosette leaves, leaf shape, the length-to-width ratio of the lamina, and paraffin section of shoot apical meristems indicated that vegetative phase change in gi was delayed. Moreover, the RT-PCR and q-PCR of miR156, a key molecular factor regulating VPC, showed equivalent consequence with morphological and anatomical analysis. Compared with wild plants, multi-layers of tunica cells were onset later, corpus and pith meristem zone developed later in mutant plants, due to the changed growth rhythms controlled by the circadian clock. Our data suggested that GI might play a role in regulating plant VPC through affecting the development of SAM.

Key words: vegetative phase change, circadian clock, gi, Arabidopsis thaliana