Abstract
A homolog of MOTHER OF FT AND TFL1 (MFT) was isolated from Hevea brasiliensis and its biological function was investigated. Protein multiple sequence alignment and phylogenetic analysis revealed that HbMFT1 conserved critical amino acid residues to distinguish MFT, FLOWERING LOCUS T (FT) and TERMINAL FLOWER1 (TFL1)-like proteins and showed a closer genetic relationship to the MFT-like group. The accumulation of HbMFT1 was generally detected in various tissues except pericarps, with the highest expression in embryos and relatively higher expression in roots and stems of seedlings, flowering inflorescences, and male and female flowers. HbMFT1 putative promoter analysis showed that tissue-specific, environmental change responsive and hormone-signaling responsive elements were generally present. HbMFT1 was strongly induced under a short-day condition at 28 °C, with the highest expression after the onset of a day. Overexpression of HbMFT1 inhibited seed germination, seedling growth, and flowering in transgenic Arabidopsis. The qRT-PCR further confirmed that APETALA1 (AP1) and FRUITFULL (FUL) were drastically down-regulated in 35S::HbMFT1 plants. A histochemical β-glucuronidase (GUS) assay showed that HbMFT1::GUS activity was mainly detected in stamens and mature seeds coinciding with its original expression and notably induced in rosette leaves and seedlings of transgenic Arabidopsis by exogenous abscisic acid (ABA) due to the presence of ABA cis-elements in HbMFT1 promoter. These results suggested that HbMFT1 was mainly involved in maintenance of seed maturation and stamen development, but negatively controlled germination, growth and development of seedlings and flowering. In addition, the HbMFT1 promoter can be utilized in controlling transgene expression in stamens and seeds of rubber tree or other plant species.
Highlights
Rubber tree, a member of Euphorbiaceae family [1], is a monoecious species with male and female flowers on the same inflorescence and is known as an economically important crop in that it can produce natural rubber which is widely used in various aspects, such as in the rubber industry, medical health and items used in daily life because of its particular features of strong flexibility, good insulation, and plasticity as well asits waterproof quality
A 2267 bp 51 flanking region upstream of HbMFT1 coding region was cloned using a pair of specific primers and a 151 bp 31 untranslated region (UTR) was obtained by 31 rapid amplification of cDNA ends (RACE)
At position His88/Tyr85 in the TERMINAL FLOWER1 (TFL1)/FLOWERING LOCUS T (FT)-like protein, HbMFT1 contained other Trp88-like MOTHER OF FT AND TFL1 (MFT) homologs, suggesting that Trp88 is highly conserved for function in MFT homologs among different species because His88/Tyr85 conferred TFL1/FT function in other plants [27,28]
Summary
A member of Euphorbiaceae family [1], is a monoecious species with male and female flowers on the same inflorescence and is known as an economically important crop in that it can produce natural rubber which is widely used in various aspects, such as in the rubber industry, medical health and items used in daily life because of its particular features of strong flexibility, good insulation, and plasticity as well asits waterproof quality. For higher yield many of the agronomic and economic traits of rubber trees need to be improved, such as low temperature tolerance, strong-wind resistance, as well as pest and disease resistance. Conventional breeding programs have been conducted to improve these traits for many decades, and it has taken more than 28 years to breed and select a new clone for commercial production. Molecular breeding provides an advantageous genetic improvement method to obtain desirable traits and speed up the Hevea breeding program. Tissue-specific promoters used for control of incorporation and expression of exogenous genes will contribute greatly to improvement of the traits in special organs and tissues
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