Figures (1)  Tables (1)

    • Figure 1. 

      The regeneration-promoting effect of WUS, BBM, GRFs, and GRFs–GRFs genes in plant transformation. In standard plant transformation systems, transgene is delivered into selected explants, plant tissue culture is used to induce plant regeneration, then the final transgenic plants are selected from regenerated plants. Among them, plant regeneration is often the bottleneck of the process. Genes WUS, BBM, GRFs, and GRFs–GRFs (red) could promote plant regeneration via either organogenesis or somatic embryogenesis in various plant species.

    • Gene*PromoterExplantsEffectsRef.
      AtWUSEstrogen-inducibleA. thaliana rootHigh somatic embryo formation frequency[15]
      Estrogen-inducibleNicotiana tabacum leafShoot formation from root tip[20]
      35SGossypium hirsutum hypocotylShoot formation from root tip[16]
      vsp1Medicago truncatula seedling radicle47.75% increase in embryogenic callus formation[18]
      ZmWUS2ZmPLTP Zea mays immature embryoEnhanced callogenesis and embryogenesis[66]
      NosA. thaliana (seedling), Solanum lycopersicum (seedling), N. tabacum (seedling/mature plant), Solanum tuberosum (mature plant), Vitis. vinifera (mature plant)de novo meristem induction[38]
      AtWUS-GR, AtSTM-GR35SA. thaliana (floral dip)Triggered ectopic organogenesis[18]
      AtWUS, CHAP3A (PmLEC1)Estrogen-induciblePicea glauca immature embryoDid not induce somatic embryogenesis[59]
      eGFP-GhWUS1a, eGFP-GhWUS1bEstrogen-inducibleG. hirsutum hypocotylInhibited embryogenic callus formation[60]
      AtBBM, BnBBM35S, inducibleN. tabacum leafEnhance the regeneration capacity[24]
      BcBBM35SPopulus tomentosa calliPlant regeneration through somatic embryogenesis[25]
      BnBBM35S, HnUbB1A. thaliana (floral dip) B. napus haploid embryoSpontaneous formation of somatic embryos and cotyledon-like structures[22]
      BnBBM
      EgAP2-1 (BBM)      		35SCapsicum. annuum cotyledonMade recalcitrant pepper transformable[23]
      35SA. thaliana (floral dip)Enhanced regeneration capacity[63]
      GmBBM135SA. thaliana (floral dip)Induced somatic embryos on vegetative organs[64]
      TcBBM35SA. thaliana (floral dip)Enhanced/hormone-independent somatic[65]
      AtBBM-GR35SA. thaliana (floral dip)Improved plant regeneration for extended periods of time in tissue culture[62]
      HvWUS, HvBBMZmAxig1, ZmPLPTHordeum vulgareCo-expression increased transformation efficiency by 3 times[61]
      ZmBBM+ZmWUS2ZmUbi, NosZ. mays immature embryo, mature embryo, seedling leaf segment; Oryza sativa calli; Sorghum bicolor immature embryo; Saccharum officianrum calliEnabled transformation of recalcitrant varieties and/or increased transformation efficiency[26−28]
      ZmAxig1, ZmPLTPZ. mays immature embryoEstablished rapid callus-free transformation[29]
      ZmPLTPS. bicolor immature embryoReduced genotype dependence, accelerated regeneration, increased transformation efficiency[67]
      AtGRF5/BvGRF5-L2×35SBeta. vulgaris cotyledon, hypocotylEnabled transformation of recalcitrant varieties. Increased transformation efficiency[33]
      AtGRF5/HaGRF5-L2×35SHelianthus annuus cotyledonImproved transgenic shoot formation
      GmGRF5-LPcUbi4-2Glycine. max primary nodeImproved transgenic shoot formation
      BnGRM5-LPcUbi4-2B. napus hypocotylPromoted callus production
      ZmGRF5-L1/2BdEF1Z. mays immature embryo)Increased transformation efficiency ~3 times
      TaGRF4-GIF1ZmUbiTriticum aestivum immature embryoIncreased regeneration efficiency 7.8 times; shortened protocol[34]
      O. sativa calli from seedsIncreased regeneration efficiency 2.1 times
      ClGRF41-GIF1/VvGRF4-GIF135SCitrus limon etiolated epicotylIncreased regeneration efficiency ~4.7 times
      CIGRF42-GIF135SCitrullus lanatus cotyledonIncreased transformation efficiency ~9 times[68]
      *At, A. thaliana; Zm, Z. mays; Pm, Picea mariana; Gh, G. hirsutum; Bn, B. napus; Bc, B. campestris; Eg, Elaeis guineensis; Gm, G. max; Tc, Theobroma cacao; Hv, H. vulgare; Bv, B. vulgaris; Ta, T. aestivum; Cl, 1C. limon, 2C. lanatus; Vv, V. vinifera.

      Table 1. 

      The effects of WUS, BBM, GRFs, and GRFs–GRFs on plant development and genetic transformation.