Gibberelin Mutants Ga3-1 And Ga5-1 Vegetative Phase Change In Arabidopsis Thaliana

The plant development includes three major process:embryosis, vegetative phase and reproductive phase. The vegetative phase composed with juvenile phase and adult phase. Vegetative phase change (VPC) of Arabidopsis thaliana refers to the transition of juvenile phase to adult phase during vegetative growth. So far, the regulation mechanism of VPC still remains unknown, but it indeed involves variety of species-specific traits, such as rosette leaf shape, onset of the first leaf with abaxial trichomes and structure of shoot apical meristem (SAM) and so on. Ortherwise, as one of the five major hormones in plant, the function of gibberellins acted in this process is also unclear.In our research, we observed the growth cycle, rosette leaf shape, plastochron, onset of the first leaf with abaxial trichomes and structure of shoot apical meristem (SAM) of Arabidopsis thaliana wild-type and gibberellins lost-of-function mutants, ga3-1 and ga5-1. The results show that, In ga3-1, because of GA treatments in its early development stage, its germination, onset of first rosette leaf and flower buds advanced, and its bolting, first flower open and seed harvest all delayed. Germination, onset of first rosette leaf and flower buds, bolting, first flower open and seed harvest all delayed in ga5-1 but advanced in GA treatments plants showing the positive affections of GA in Arabidopsis thaliana whole development process. Also VPC was delayed in these late flowering mutants, indicating the close relationship between VPC and reproductive phase change. Juvenile rosette leaf increased in both gibberellins lost-of-function mutants in spite of the GA treatments in ga3-1’s early development stage; GA treatment decreased juvenile rosette leaf but unable to onset abaxial trichomes on the first couple of rosette leaves in Arabidopsis thaliana. indicating that GA promote the onset of the first leaf with abaxial trichomes in Arabidopsis thaliana.and there maybe exists a mechanism blocking GA affection pathways during juvenile phase in Arabidopsis thaliana.. The length-width ratio of rosette leaf in ga3-1 decreased which is contrary with the wild type showing that a larger drop of GA level strongly influnced the shape of rosette leaf in Arabidopsis thaliana.Meristem cell ratio in SAM declined in all wild-type and gibberellins lost-of-function, indicating onset of first rosette leaf and structure of SAM acted as species-specific traits of VPC.miR156 and its target genes SPLs are considered as general regulator of phase change transitions in Arabidopsis thaliana.. The expreesion of miR156 and SPL3 Arabidopsis thaliana wild-type and gibberellins lost-of-function mutants presents significant decrease and increase tendency confirming their major regulator role in this process and the gibberellins lost-of-function mutant is unconcerned in their expression. While the expression of SPL4 and SPL5 in both gibberellins lost-of-function mutants shows remarkable difference from the wild-type, especially the expression of SPL5 shows remarkable difference between the two mutants suggesting GA regulating this process through changing the expression of SPL4 and SPL5.