title: FTIP1 is an essential regulator required for florigen transport.
abstract: The capacity to respond to day length, photoperiodism, is crucial for flowering plants to adapt to seasonal change. The photoperiodic control of flowering in plants is mediated by a long-distance mobile floral stimulus called florigen that moves from leaves to the shoot apex. Although the proteins encoded by FLOWERING LOCUS T (FT) in Arabidopsis and its orthologs in other plants are identified as the long-sought florigen, whether their transport is a simple diffusion process or under regulation remains elusive. Here we show that an endoplasmic reticulum (ER) membrane protein, FT-INTERACTING PROTEIN 1 (FTIP1), is an essential regulator required for FT protein transport in Arabidopsis. Loss of function of FTIP1 exhibits late flowering under long days, which is partly due to the compromised FT movement to the shoot apex. FTIP1 and FT share similar mRNA expression patterns and subcellular localization, and they interact specifically in phloem companion cells. FTIP1 is required for FT export from companion cells to sieve elements, thus affecting FT transport through the phloem to the SAM. Our results provide a mechanistic understanding of florigen transport, demonstrating that FT moves in a regulated manner and that FTIP1 mediates FT transport to induce flowering.
authors.affiliation: Department of Biological Sciences and Temasek Life Sciences Laboratory, National University of Singapore, Singapore.
authors.forename: Lu
authors.initials: L
authors.lastname: Liu
authors.forename: Chang
authors.initials: C
authors.lastname: Liu
authors.forename: Xingliang
authors.initials: X
authors.lastname: Hou
authors.forename: Wanyan
authors.initials: W
authors.lastname: Xi
authors.forename: Lisha
authors.initials: L
authors.lastname: Shen
authors.forename: Zhen
authors.initials: Z
authors.lastname: Tao
authors.forename: Yue
authors.initials: Y
authors.lastname: Wang
authors.forename: Hao
authors.initials: H
authors.lastname: Yu
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D004721:Endoplasmic Reticulum / Q000378:metabolism; D025461:Feedback, Physiological; D060405:Florigen / Q000378:metabolism*; D015870:Gene Expression; D018506:Gene Expression Regulation, Plant; D056626:Inflorescence / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D052585:Phloem / Q000166:cytology / Q000378:metabolism; D030821:Plants, Genetically Modified; D055550:Protein Stability; D021381:Protein Transport; D020871:RNA Stability; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; C418905:FT protein, Arabidopsis; C574085:FTIP1 protein, Arabidopsis; D060405:Florigen; D008565:Membrane Proteins; D012333:RNA, Messenger