Reevaluation of florigen transport kinetics with separation of function mutations that uncouple flowering initiation and long-distance transport

• Published in: Plant and cell physiology
• Main Authors: Endo, Motomu, Yoshida, Masayasu, Sasaki, Youhei, Negishi, Katsuya, Horikawa, Kobo, Daimon, Yasufumi, Kurotani, Ken-Ichi, Notaguchi, Michitaka, Abe, Mitsutomo, Araki, Takashi
• Format: Journal Article
• Language: English
• Published: Japan 19.03.2018
• ISSN: 1471-9053

In many plants, timing of flowering is regulated by day length. In Arabidopsis, florigen, FLOWERING LOCUS T (FT) protein, is synthesized in leaf phloem companion cells in response to long days and is transported to the shoot apical meristem (SAM) through the phloem. The temporal aspects of florigen transportation have been studied in various plants by physiological experiments. Nevertheless, little is known how FT protein transportation is regulated in Arabidopsis. In this study, we performed heat-shock based transient FT induction in a single leaf blade and detected the FT protein in shoot apex by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE). We demonstrated that detectable amounts of FT were transported from the leaf to shoot apex within 8 h, and subsequent FT-induced target gene expression was detected within 8-12 h. Furthermore, we identified three amino acid residues (V70, S76 and R83) where missense mutations led to reduced mobility. Interestingly, these FT variants lost only their transportation ability, but retained their flowering promotion capacity, suggesting that discrete amino acids are involved in flowering regulation and transport regulation. Since the interaction with FT-INTERACTING PROTEIN 1 (FTIP1) was not affected in these FT variants, we hypothesize that the three amino acid residues are not involved in the FTIP1-mediated pathway of uploading, but rather in the subsequent step(s) of FT transport.