Mobile FT mRNA contributes to the systemic florigen signalling in floral induction.
Li C., Gu M., Shi N., Zhang H., Yang X., Osman T., Liu Y., Wang H., Vatish M., Jackson S., Hong Y.
In inducing photoperiodic conditions, plants produce a signal dubbed "florigen" in leaves. Florigen moves through the phloem to the shoot apical meristem (SAM) where it induces flowering. In Arabidopsis, the FLOWERING LOCUS T (FT) protein acts as a component of this phloem-mobile signal. However whether the transportable FT mRNA also contributes to systemic florigen signalling remains to be elucidated. Using non-conventional approaches that exploit virus-induced RNA silencing and meristem exclusion of virus infection, we demonstrated that the ArabidopsisFT mRNA, independent of the FT protein, can move into the SAM. Viral ectopic expression of a non-translatable FT mRNA promoted earlier flowering in the short-day (SD) Nicotiana tabacum Maryland Mammoth tobacco in SD. These data suggest a possible role for FT mRNA in systemic floral signalling, and also demonstrate that cis-transportation of cellular mRNA into SAM and meristem exclusion of pathogenic RNAs are two mechanistically distinct processes.