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    • It has been reported that the FDP synthase

    2022-03-18

    It has been reported that the FDP synthase in Hevea latex has a major role to produce the starter substrate FPP for the prenyl chain elongation in natural rubber biosynthesis (Takaya et al., 2003). Accumulation of HbFDP mRNA transcripts in different tissue types including latex (natural rubber) producing laticifer vadadustat was evaluated by semi-quantitative RT-PCR. The level of mRNA transcript accumulation was more abundant in laticifer cells than in other tissues such as leaf, immature leaf and young seedlings. In Hevea, a plant used for production of natural rubber, HbFDP is expressed predominantly in the laticifer tissue type, the cells specific to rubber biosynthesis. It is presumed that the differential expression pattern is likely to be correlated with the active role of the HbFDP enzyme in polyisoprene production within the laticiferous tissues (latex producing cells) during the natural rubber biosynthesis (Pan et al., 1996, Takaya et al., 2003). Semi-quantitative RT-PCR results showed that the expression level of the HbFDP in laticifer cells was found to be significantly higher and is presumed to be involved in natural rubber (cis-1,4-polyisoprene) biosynthesis, since laticifers are the sites for rubber biosynthesis. As expected, the highest mRNA transcript levels of HbFDP were observed in laticifer cells while the lowest level of HbFDP mRNA expression was noticed in leaf tissues. As FPS appears to be associated with rubber particles, FPS activity is linked to rubber biosynthesis in Guayule (Pan et al., 1996). The occurrence of FDP isozymes raises the question about the role of each individual FPS isoform in the isoprenoid biosynthesis. As the cloned HbFDP gene had shared high similarity with Arabidopsis FPS2 isoform, this gene may play a very important role in early development of plants (Closa et al., 2010, Keim et al., 2012). It has been reported that FPS1 is widely expressed in all types of tissues within the plant development whereas expression of FPS2 is mainly found in floral organs, seeds and the early stages of seedling development (Keim et al., 2012). Therefore, the cloned HbFDP gene was over-expressed in transgenic Arabidopsis and studied the possible involvement of this gene in isoprenoid biosynthesis and plant growth and development. The semi-quantitative RT-PCR analysis with three independent Arabidopsis transgenic lines expressing FDP showed that the accumulation of FDP mRNA transcripts was found to be high in transgenic lines compared to that of control wild-type. The RT-PCR results clearly showed that abundance of mRNA transcript level was significantly different among the transgenic lines compared to the control. Transgenic plants showed higher biomass with good growth rate than control. The present results are incorporated with earlier reports (Chen et al., 2000, Sun et al., 2013). Sun et al. (2013) developed transgenic plants over-expressed with MsFPPS gene in tobacco and reported the significant role of this gene in plant growth regulation and phytosterol production. However, there was no significant difference observed between the phenotypes of transgenic plants over-expressing MsGPPS and MsGGPPS and wild-type tobacco plant (Sun et al., 2013). Also, Chen et al. (2000) reported that a full-length cDNA encoding FPS was isolated from a Gossypium arboreum and transformed into the A. annua. As a result the artemisinin content was increased 2–3 fold in transgenic plants. Similarly, Venkatachalam et al. (2009) described that the accumulation of HMGR1 mRNA transcripts was 3–5 fold higher in Arabidopsis transgenic lines compared to the wild plants. In contrast, Masferrer et al. (2002) reported that Arabidopsis plants over-expressing with FPS1S gene exhibited a premature senescence-like phenotype and grew less vigorously than wild-type plants. One of the possible reasons for enhanced growth of Arabidopsis plants over-expressing with HbFDP gene in the present study is that the HbFDP gene shared high homology with Arabidopsis FPS2 which is experimentally proved to be involved in regulation of seedling growth.