Department of Plant Sciences, The Pennsylvania State University, University Park, PA, USA.
Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, PA, USA.
BMC Plant Biol. 2021 May 14;21(1):218. doi: 10.1186/s12870-021-02982-y.
In angiosperms the transition to flowering is controlled by a complex set of interacting networks integrating a range of developmental, physiological, and environmental factors optimizing transition time for maximal reproductive efficiency. The molecular mechanisms comprising these networks have been partially characterized and include both transcriptional and post-transcriptional regulatory pathways. Florigen, encoded by FLOWERING LOCUS T (FT) orthologs, is a conserved central integrator of several flowering time regulatory pathways. To characterize the molecular mechanisms involved in controlling cacao flowering time, we have characterized a cacao candidate florigen gene, TcFLOWERING LOCUS T (TcFT). Understanding how this conserved flowering time regulator affects cacao plant's transition to flowering could lead to strategies to accelerate cacao breeding.
BLAST searches of cacao genome reference assemblies identified seven candidate members of the CENTRORADIALIS/TERMINAL FLOWER1/SELF PRUNING gene family including a single florigen candidate. cDNA encoding the predicted cacao florigen was cloned and functionally tested by transgenic genetic complementation in the Arabidopsis ft-10 mutant. Transgenic expression of the candidate TcFT cDNA in late flowering Arabidopsis ft-10 partially rescues the mutant to wild-type flowering time. Gene expression studies reveal that TcFT is spatially and temporally expressed in a manner similar to that found in Arabidopsis, specifically, TcFT mRNA is shown to be both developmentally and diurnally regulated in leaves and is most abundant in floral tissues. Finally, to test interspecies compatibility of florigens, we transformed cacao tissues with AtFT resulting in the remarkable formation of flowers in tissue culture. The morphology of these in vitro flowers is normal, and they produce pollen that germinates in vitro with high rates.
We have identified the cacao CETS gene family, central to developmental regulation in angiosperms. The role of the cacao's single FT-like gene (TcFT) as a general regulator of determinate growth in cacao was demonstrated by functional complementation of Arabidopsis ft-10 late-flowering mutant and through gene expression analysis. In addition, overexpression of AtFT in cacao resulted in precocious flowering in cacao tissue culture demonstrating the highly conserved function of FT and the mechanisms controlling flowering in cacao.
在被子植物中，开花的转变由一系列复杂的相互作用网络控制，这些网络整合了一系列发育、生理和环境因素，以优化最大生殖效率的转变时间。这些网络的分子机制已经部分得到了描述，包括转录和转录后调控途径。Florigen 由 FLOWERING LOCUS T (FT) 同源物编码，是几个开花时间调控途径的保守中央整合因子。为了表征控制可可开花时间的分子机制，我们对可可候选 Florigen 基因 TcFLOWERING LOCUS T (TcFT) 进行了表征。了解这个保守的开花时间调节因子如何影响可可植物的开花转变，可能会导致加速可可育种的策略。
对可可基因组参考组装的 BLAST 搜索鉴定了 CENTRORADIALIS/TERMINAL FLOWER1/SELF PRUNING 基因家族的七个候选成员，包括一个单一的 Florigen 候选物。通过在拟南芥 ft-10 突变体中的转基因遗传互补，克隆并功能测试了预测可可 Florigen 的 cDNA。候选 TcFT cDNA 在晚开花的拟南芥 ft-10 中的转基因表达部分挽救了突变体向野生型开花时间。基因表达研究表明，TcFT 在空间和时间上的表达方式与在拟南芥中发现的相似，具体而言，TcFT mRNA 在叶片中表现出发育和昼夜调节，并且在花组织中最为丰富。最后，为了测试 Florigens 的种间相容性，我们用 AtFT 转化可可组织，导致组织培养中惊人的花朵形成。这些体外花的形态正常，花粉在体外具有高发芽率。
我们已经鉴定了可可 CETS 基因家族，这是被子植物发育调控的核心。通过拟南芥 ft-10 晚花突变体的功能互补和基因表达分析，证明了可可单 FT 样基因（TcFT）作为可可定长生长的一般调节因子的作用。此外，AtFT 在可可中的过表达导致可可组织培养中的早熟开花，证明了 FT 的高度保守功能和控制可可开花的机制。
