Dataset Information

Inter-species functional compatibility of the Theobroma cacao and Arabidopsis FT orthologs: 90 million years of functional conservation of meristem identity genes.

ABSTRACT:

Background

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.

Results

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.

Conclusion

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.

SUBMITTER: Prewitt SF

PROVIDER: S-EPMC8122565 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Similar Datasets

Project description:BACKGROUND: The Arabidopsis thaliana NPR1 gene encodes a transcription coactivator (NPR1) that plays a major role in the mechanisms regulating plant defense response. After pathogen infection and in response to salicylic acid (SA) accumulation, NPR1 translocates from the cytoplasm into the nucleus where it interacts with other transcription factors resulting in increased expression of over 2000 plant defense genes contributing to a pathogen resistance response. RESULTS: A putative Theobroma cacao NPR1 cDNA was isolated by RT-PCR using degenerate primers based on homologous sequences from Brassica, Arabidopsis and Carica papaya. The cDNA was used to isolate a genomic clone from Theobroma cacao containing a putative TcNPR1 gene. DNA sequencing revealed the presence of a 4.5 kb coding region containing three introns and encoding a polypeptide of 591 amino acids. The predicted TcNPR1 protein shares 55% identity and 78% similarity to Arabidopsis NPR1, and contains each of the highly conserved functional domains indicative of this class of transcription factors (BTB/POZ and ankyrin repeat protein-protein interaction domains and a nuclear localization sequence (NLS)). To functionally define the TcNPR1 gene, we transferred TcNPR1 into an Arabidopsis npr1 mutant that is highly susceptible to infection by the plant pathogen Pseudomonas syringae pv. tomato DC3000. Driven by the constitutive CaMV35S promoter, the cacao TcNPR1 gene partially complemented the npr1 mutation in transgenic Arabidopsis plants, resulting in 100 fold less bacterial growth in a leaf infection assay. Upon induction with SA, TcNPR1 was shown to translocate into the nucleus of leaf and root cells in a manner identical to Arabidopsis NPR1. Cacao NPR1 was also capable of participating in SA-JA signaling crosstalk, as evidenced by the suppression of JA responsive gene expression in TcNPR1 overexpressing transgenic plants. CONCLUSION: Our data indicate that the TcNPR1 is a functional ortholog of Arabidopsis NPR1, and is likely to play a major role in defense response in cacao. This fundamental knowledge can contribute to breeding of disease resistant cacao varieties through the application of molecular markers or the use of transgenic strategies.