The Role And Mechanism Of A Wheat BZIP Gene TαGBF In Regulating Flowering Time

Light is a very important environment factor in the process of the plant growth and development from seed germination to flowering.Plants have distinct photo receptors to sense light in different spectrum. Cryptochrome, the blue light receptors, were reported to participate in the regulation of plant flowering process, mainly via the photoperiod pathway.TaGBF gene was cloned and studied preliminarily based on the suppression subtractive hybridization (SSH) and microarray data of a new wheat introgression ShanRong3 (SR3) in stress tolerance. According to the previous study, TaGBF was epistatical to CRY1 in blue light signaling pathway and promoted photomorphogenesis. Furthermore, the study showed that overexpression of TaGBF in Arabidopsis thaliana delayed flowering. We speculated that overexpression of TaGBF gene in wheat may inhibit the formation of floral organ, as an important modulator integrating blue light pathway and flowering pathways. The main contents and results achieved in this research were summarized as follows:1. The CO gene is regulated by TaGBFOverexpression of TaGBF in Arabidopsis thaliana and wheat down-regulated the expression of CO gene. In TaGBFox seedlings, the expression of CO regulating-factors, such as CDF1, CDF2, FKF1, FBH1, FBH2, FBH3, FBH4, ELF3 and COP1 was not significantly changed. The co-2 mutants was crossed with TaGBF overexpression seedlings, and TaGBF was epistatical to CO in the co-2/TaGBFox seedlings. The down-regulation of CO gene in overexpression seedlings is suggested to be a main reason for the delay flowering.2. The FT gene is regulated by TaGBFOverexpression of TaGBF in Arabidopsis thaliana and wheat inhibited the expression of FT gene. TaGBF gene affected not only the expression of CO gene but also the expression of FT under long day time. In co-2/TaGBFox seedlings with higher expression level of TaGBF, the flowering time was later and the expression of FT was lower. CIBox seedlings was crossed with TaGBFox seedlings. Consequence showed that overexpression of TaGBF inhibited the up-regulation of FT expression caused by CIB in CIBox/TaGBFox seedlings. The down-regulation of FT expression may contribute to the delay flowering.3. The interaction between TaGBF and gene to Gibberellin signaling pathwayThe flowering time was significantly delayed in TaGBF over-expressing seedlings under short day time. Furthermore, the TaGBF over-expressing seedlings was insensitive to gibberellins. Exogenous gibberellins led to early flowering in wild type Arabidopsis while not in TaGBFox seedlings. The expression of GA synthesis genes was up-regulated while degradation genes were down-regulated.4. The influence of TaGBF gene to leaf developmentThe leaf size of TaGBF over-expressing seedlings is larger than that of wild-type under short day time. The expression of genes controlling leaf cell number such as GRFs and TCPs was significantly changed in TaGBF over-expressing seedlings.