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Functional analysis of alternative splicing of the FLOWERING LOCUS T orthologous gene in Chrysanthemum morifolium

View Article: PubMed Central - PubMed

ABSTRACT

As the junction of floral development pathways, the FLOWERING LOCUS T (FT) protein called ‘florigen’ plays an important role in the process of plant flowering through signal integration. We isolated four transcripts encoding different isoforms of a FT orthologous gene CmFTL1, from Chrysanthemum morifolium cultivar ‘Jimba’. Sequence alignments suggested that the four transcripts are related to the intron 1. Expression analysis showed that four alternative splicing (AS) forms of CmFTL1 varied depending on the developmental stage of the flower. The functional complement experiment using an Arabidopsis mutant ft-10 revealed that the archetypal and AS forms of CmFTL1 had the function of complementing late flower phenotype in different levels. In addition, transgenic confirmation at transcript level showed CmFTL1 and CmFTL1ast coexist in the same tissue type at the same developmental stage, indicating a post-transcriptional modification of CmFTL1 in Arabidopsis. Moreover, ectopic expression of different AS forms in chrysanthemum resulted in the development of multiple altered phenotypes, varying degrees of early flowering. We found that an alternative splicing form (CmFTL1-astE134) without the exon 2 lacked the ability causing the earlier flower phenotype. The evidence in this study indicates that complex alternative processing of CmFTL1 transcripts in C. morifolium may be associated with flowering regulation and hold some potential for biotechnical engineering to create early-flowering phenotypes in ornamental cultivars.

No MeSH data available.


The floral transition in chrysanthemum wild type and CmFTL1 transgenic lines. EO, early opening stage; FBD, flower bud development stage; OF, open flower stage; SF stage, senescent flower stage; VC, visible colour stage. Scale Bars, 1 cm.
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fig4: The floral transition in chrysanthemum wild type and CmFTL1 transgenic lines. EO, early opening stage; FBD, flower bud development stage; OF, open flower stage; SF stage, senescent flower stage; VC, visible colour stage. Scale Bars, 1 cm.

Mentions: To investigate the potential function of CmFTL1 and CmFTL1asts in chrysanthemum, transgenic chrysanthemum plants with CmFTL1 and CmFTL1asts expressed under the control of the Cauliflower mosaic virus (CaMV) 35S promoter were generated, named by OX-CmFTL1 or OX-CmFTL1asts (Supplementary Figures 4–6). The phenotypes of transgenic lines were observed under natural conditions. The flower development of chrysanthemum involves six stages: before flower bud development stage, flower bud development stage (FBD), visible colour stage (VC) stage, earlier opening stage, opened flower stage and senescing flower stage.22 The FBD and the VC stage of OX-CmFTL1astIn1-1 and OX-CmFTL1astIn1-2 lines were both advanced by 5–8days, while OX-CmFTL1astIn1-3 lines were advanced only by 2–4 days. No significant alteration to flowering time was noted in the transgenic plants constitutively expressing CmFTL1astE134 and wild-type plants (Figure 4). The qRT-PCR and qPCR analyses showed that in wild-type plants, the abundance of CmFTL1 transcript peaked at the early flower bud development stage (Figure 5). Although the temporal pattern of the AS forms was similar to the wild type, their transcript abundance was much lower. However, the AS transcripts were higher than the CmFTL1 in the AS transgenic chrysanthemum plants (Figure 6). The results suggested that the CmFTL1 AS transcripts underwent post-transcriptional processing, similar to the CmFTL1ast A. thaliana transgenic lines, resulting in an increased abundance of the archetypal transcript.


Functional analysis of alternative splicing of the FLOWERING LOCUS T orthologous gene in Chrysanthemum morifolium
The floral transition in chrysanthemum wild type and CmFTL1 transgenic lines. EO, early opening stage; FBD, flower bud development stage; OF, open flower stage; SF stage, senescent flower stage; VC, visible colour stage. Scale Bars, 1 cm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5120556&req=5

fig4: The floral transition in chrysanthemum wild type and CmFTL1 transgenic lines. EO, early opening stage; FBD, flower bud development stage; OF, open flower stage; SF stage, senescent flower stage; VC, visible colour stage. Scale Bars, 1 cm.
Mentions: To investigate the potential function of CmFTL1 and CmFTL1asts in chrysanthemum, transgenic chrysanthemum plants with CmFTL1 and CmFTL1asts expressed under the control of the Cauliflower mosaic virus (CaMV) 35S promoter were generated, named by OX-CmFTL1 or OX-CmFTL1asts (Supplementary Figures 4–6). The phenotypes of transgenic lines were observed under natural conditions. The flower development of chrysanthemum involves six stages: before flower bud development stage, flower bud development stage (FBD), visible colour stage (VC) stage, earlier opening stage, opened flower stage and senescing flower stage.22 The FBD and the VC stage of OX-CmFTL1astIn1-1 and OX-CmFTL1astIn1-2 lines were both advanced by 5–8days, while OX-CmFTL1astIn1-3 lines were advanced only by 2–4 days. No significant alteration to flowering time was noted in the transgenic plants constitutively expressing CmFTL1astE134 and wild-type plants (Figure 4). The qRT-PCR and qPCR analyses showed that in wild-type plants, the abundance of CmFTL1 transcript peaked at the early flower bud development stage (Figure 5). Although the temporal pattern of the AS forms was similar to the wild type, their transcript abundance was much lower. However, the AS transcripts were higher than the CmFTL1 in the AS transgenic chrysanthemum plants (Figure 6). The results suggested that the CmFTL1 AS transcripts underwent post-transcriptional processing, similar to the CmFTL1ast A. thaliana transgenic lines, resulting in an increased abundance of the archetypal transcript.

View Article: PubMed Central - PubMed

ABSTRACT

As the junction of floral development pathways, the FLOWERING LOCUS T (FT) protein called ‘florigen’ plays an important role in the process of plant flowering through signal integration. We isolated four transcripts encoding different isoforms of a FT orthologous gene CmFTL1, from Chrysanthemum morifolium cultivar ‘Jimba’. Sequence alignments suggested that the four transcripts are related to the intron 1. Expression analysis showed that four alternative splicing (AS) forms of CmFTL1 varied depending on the developmental stage of the flower. The functional complement experiment using an Arabidopsis mutant ft-10 revealed that the archetypal and AS forms of CmFTL1 had the function of complementing late flower phenotype in different levels. In addition, transgenic confirmation at transcript level showed CmFTL1 and CmFTL1ast coexist in the same tissue type at the same developmental stage, indicating a post-transcriptional modification of CmFTL1 in Arabidopsis. Moreover, ectopic expression of different AS forms in chrysanthemum resulted in the development of multiple altered phenotypes, varying degrees of early flowering. We found that an alternative splicing form (CmFTL1-astE134) without the exon 2 lacked the ability causing the earlier flower phenotype. The evidence in this study indicates that complex alternative processing of CmFTL1 transcripts in C. morifolium may be associated with flowering regulation and hold some potential for biotechnical engineering to create early-flowering phenotypes in ornamental cultivars.

No MeSH data available.