| Summary: | 碩士 === 國立中央大學 === 生命科學研究所 === 95 === In higher plants, the determination of the transition from vegetative to reproductive stage is one of the most important steps during their developmental courses. In order to produce offspring at optimal environmental conditions, plants must response to the variations of ambient condition and adjust their reproductive transition. From classic grafting experiments, it has been established that after plants receiving day-length difference, florigen, the floral stimuli, are synthesized in the leaves and then transported long-distance through phloem to trigger flowering at apices. Previous studies have shown that the protein of FLOWERING LOCUS T (FT) may act as a florigen-like molecule in Arabidopsis and rice. However, while FT protein movement is restricted by expressing a strong FT-binding protein in vascular tissues, the flowering time is not delayed, suggesting that other florigen-like molecule, probably FT mRNA, may act redundantly to trigger floral initiation. To test this
possibility, we first determined the existence of FT mRNA in the phloem sap. By using RT-PCR analysis, FT mRNA is detected in the phloem sap collected from Brassica oleracea, a species closely related to Arabidopsis. To further test the long-distance movement of FT mRNA, the Arabidopsis grafting experiments were conducted. Our results show that the chimeric FT mRNA except FT-EGFP can move long-distance trough grafting unit. In addition, the
detection of FT mRNA in the scion apices is well correlated with the floral promotion in the scions. Taken together, we propose that both FT mRNA and protein may act redundantly as florigens to regulate flowering time.
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