Figures (2)  Tables (2)
    • Figure 1. 

      Mobile proteins and RNAs in plant development and stress response. The mobile regulators participate widely in the development of different organs (as illustrated). They can travel short-range to regulate local tissue patterning or long-distance to transduce systemic signaling. Gray arrow: phloem-based long-distance movement. WUS and STM regulate SAM maintenance; SPCH, BdMUTE, AN3, TTG1, GL3 and CPC are involved in epidermal patterning. In roots, PLT2, SHR, AtDof4.1, AHL3/AHL4, WOX5, TMO7, UBP1 and SCL23 govern a variety of processes including cell division, radial patterning, stem cell maintenance and developmental transition. Long-distance signaling regulators such as FT and HY5 can traffic from leaves to SAM to promote flowering, and from shoot to root to regulate root growth and nitrate uptake respectively. Environmental stresses can induce PD closure. Small RNAs including miR399d, 827 and 2111 move from aerial parts to roots in response to phosphate starvation.

    • Figure 2. 

      Regulation of PD permeability by callose. (a) Schematic illustration of regulation of the PD aperture by callose deposition in flanking regions of PD. Induced callose accumulation closes PD permeability and blocks the intercellular movement of transcription factors and small RNAs. (b) The design of ‘icals3m’ system that can inducibly (via estradiol induction cassette) promote callose deposition in specific cell types (via cell-type specific promoters)[128],[138].

    • Mobile TFsFunctionMoves from:toReference
      HY5Root growth and N uptakeShoot-to-rootChen et al. (2016)[41]
      DWARF14Regulate the development of AMsThrough phloem into axillary meristems (AMs)Kameoka et al. (2016)[139]
      BdMUTEBdMUTE is required for subsidiary cell formationGMCs to neighboring cell filesRaissig et al. (2017)[97]
      SPCHStomatal cell fateCell-to-cell diffusion in the leaf epidermis of chorusGuseman et al. (2010)[96]
      AN3Leaf developmentFrom the mesophyll to the epidermis in leavesKawade et al. (2013)[140]
      WUSMeristem maintenanceFrom the organizing centre to L1, L2 layersYadav et al. (2011)[28]
      KN1/STMMeristem maintenanceBroadly in the SAMKim et al. (2003)[31], 2005[32]
      PLT2Longitudinal root zonationLongitudinally from the root meristem forming a gradientMahonen et al. (2014)[141]; Galinha et al. (2007)[142]
      SHRRoot radial patterning and RAM maintenanceWithin Stele; Stele into endodermis, QC, CEI and CEDKoizumi et al. (2011)[44], Nakajima et al. (2001)[78]
      AHL3/AHL4Xylem specificationFrom procambium cells to the xylemZhou et al. (2013)[37]
      WOX5Stem cell maintenanceQC to CSCPi et al. (2015)[30]
      TMO7Recruitment of the hypophysisEmbryo into the upper cell of suspensorSchlereth (2010)[34]; Lu et al. (2018)[35]
      Cyp1Root growthFrom leaves to root in tomatoSpiegelman et al. (2015)[143]
      UBP1Transition from cell division to elongationStele and LRC to cells into transition/elongation zoneTsukagoshi et al. (2010)[144]
      SCL23Endodermal cell fateBidirectional radial spread and movement into meristemLong et al. (2015)[38]
      TTG1Trichome patterningAtrichoblasts into trichome initials
      CPCTrichome patterning, root hair initiationTrichome initials into Atrichoblasts; non-root hair cell into root hair cellWester et al. (2009)[90]
      GL3/EGL3Root hair initiationRoot hair cell into non-root hair cellKang et al. (2013)[91]

      Table 1. 

      Summary of the mobile transcription factors identified in plants.

    • Mobile factorFunctionMoves from: toReference
      mRNA
      KN1SAM maintenanceinjected cell to neighbouring cellsLucas et al. (1995)[26]
      SUC1Sucrose transportcompanion cells to sieve elementsKuhn et al. (1999)[145]
      FT1Flowering inductionLeaf to SAMLu et al. (2012)[60]
      Aux/IAA18Root developmentLeaf to rootNotaguchi et al. (2012)[61]
      PP16RNA transportPhloem to shoot apexXoconostle-Cazares et al. (1999)[62]
      NACPMeristem maintenancePhloem to shoot apexRuiz-Medrano et al. (1999)[146]
      StBEL5Tuber formationLeaf to rootBanerjee et al. (2009)[147]
      POTH1Leaf developmentLeaf to rootMahajan et al. (2012)[148]
      SLR/IAA14Lateral root formationShoot to rootKanehira et al. (2010)[64]
      PFP-T6Leaf developmentLeaf to leaf primordiaKim et al. (2001)[65]
      PSPathogen resistanceShoot to root and vice versaZhang et al. (2018)[149]
      GAILeaf developmenthost to parasiteRoney et al. (2007) [150]; David-Schwartz et al. (2008)[151]
      ATCFloral initiationLeaf to flower apicesHuang et al. (2012)[152]
      FVEfloral regulatorsRoot to SAMYang and Yu (2010)[153]
      AGL24floral regulatorsRoot to SAMYang and Yu (2010)[153]
      siRNA
      ta-siRNAEstablishment of leaf polaritythe adaxial to the abaxial side of the leafChitwood et al. (2009)[154]
      hc-siRNADNA methylationShoot to rootBaldrich et al. (2016)[155]
      miRNA
      miR165/166Xylem specificationendodermis into the steleCarlsbecker et al. (2010)[58]
      miR390Leaf polarityvasculature and pith region below the SAM to SAMChitwood et al. (2009)[154]
      miR394Meristem maintenanceL1 to inner layers in the shoot meristemKnauer et al. (2013)[59]
      miR395Sulfate homeostasisgraft unionsBuhtz et al. (2010)[54]
      miR399dPhosphate homeostasisshoot to root and vice versaPant et al. (2008)[156]; Lin et al. (2008)[51]
      miR172regulate tuber formationLeaf to rootMartin et al. (2009)[55]
      miR2111Phosphate homeostasis;
      Rhizobial infection;
      shoot to root and vice versaHuen et al. (2017)[52];
      Tsikou et al. (2018)[53]
      miR827Phosphate homeostasisshoot to root and vice versaHuen et al. (2017)[52]

      Table 2. 

      List of mobile RNAs with functions in organ development.