| Summary: | 博士 === 國防醫學院 === 生命科學研究所 === 97 === Plants take advantage of the vascular system to operate environmental stimulates for fine-tuning their developmental programs. Recent evidence shows that the FLOWERING LOCUS T (FT) protein is the long-sought-after florigen that integrates the photoperiod variation perceived in the leaves. However, evidence also supports that other yet-to-be identified systemic regulators participate in floral induction. To this end, we investigated phloem exudates from excised broccoli (Brassica oleracea) inflorescences. Microarray and RT-PCR analyses revealed that at least two RNAs of floral regulators, FVE and AGAMOUS-LIKE 24 (AGL24), are present in the phloem sap. Enzymatic analysis demonstrated that the phloem-sap RNAs contain a 5' cap and a polyadenlylation tail, which suggests that phloem sap contains typical mRNAs. Arabidopsis grafting experiments were used to test whether these RNAs move long distance along the phloem translocation stream. Consistent with previous reports, Arabidopsis transformants expressing FVE and AGL24 displayed an early flowering phenotype. When wild-type scions were grafted onto P35S-FVE or P35S-AGL24 transformant stocks, the RNAs of transgenic FVE and AGL24 were detected from the wild-type scions. Thus, both FVE and AGL24 RNAs can move long distance across the graft union. Our data support the notion that multiple systemic floral regulators may participate in floral regulation.
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