Abstract
Thiamine or vitamin B 1 comprises a pyrimidine moiety and a thiazole moiety. Thiamine pyrophosphate (TPP), the active form of thiamine, acts as a cofactor for various major enzymes, for example, transketolase (TK), α-ketoglutarate dehydrogenase (KGDH) and pyruvate dehydrogenase (PDH). It is suggested that TPP plays another important role, which is protecting plants against abiotic and biotic stresses such as osmotic stress. In this study, the gene transcripts of first two enzymes in thiamine biosynthesis pathway, THIC and THI1/THI4 were identified and amplified from oil palm tissues. Primers were designed based on sequence comparison of the genes from Arabidopsis thaliana , Zea mays , Oryza sativa and Alnus glutinosa . Oil palm’s responses in terms of the expression profiles of these two thiamine biosynthesis genes to an osmotic stress inducer, polyethylene glycol (PEG) were examined. The level of gene transcripts was analyzed using reverse transcriptase polymerase chain reaction (RT-PCR) and both THIC and THI1/THI4 gene transcripts were successfully amplified. The levels of transcription were measured and the results showed that the expression of THIC gene transcripts showed an increase of up to 200% in 1% PEG treated plant as compared to non-treated plant while the expression of THI1/THI4 gene transcripts showed an increase of up to 100% in treated plant as compared to non-treated plant. However, increase in concentration of PEG showed decrease in amount of transcription level for both gene transcripts. The results support the suggestion that thiamine may play an important function in plant defense against stresses as these findings may lead to an overexpression of thiamine in general. Keywords: Thiamine, vitamin B1, osmotic stress, oil palm, gene expression
Highlights
Arabidopsis thaliana thiazole biosynthetic complete cds Arabidopsis thaliana Thi1 protein mRNA, complete cds Zea mays thiamine biosynthesis1, mRNA Oryza sativa Japonica Group mRNA for thiamine biosynthetic enzyme, complete cds, clone: 12YPR001 A. glutinosa mRNA for thiazole biosynthetic enzyme
In response to stress, oil palm showed an increase in the level of gene transcripts of the first two enzymes in the thiamine biosynthesis pathway
The results proved that thiamine biosynthesis genes, namely THIC and THI1/THI4, were upregulated under osmotic stress
Summary
Thiamine is important for all living organism as it serves vital functions in carbohydrate metabolism, nicotinamide adenine dinucleotide phosphate (NADPH) and adenosine triphosphate (ATP) synthesis and . Thiamine pyrophosphate (TPP) play important roles in human nutrition and central metabolism (TuncOzdemir et al, 2009; Guan et al, 2014). Thiamine and TPP are reported as crucial stressresponse molecules in plant adaptations to counteract different abiotic stress conditions (Tunc-Ozdemir et al, 2009; Rapala-Kozik et al, 2012). Studies have shown that deficit in water status in plants has led to the rapid changes in gene expression (Yamaguchi-Shinozaki and Shinozaki, 2006; Osakabe et al, 2011). Upregulation of phytohormone synthesis, such as abscisic acid, under osmotic stress has been reported (Osakabe et al, 2013). Severe exposure to osmotic stress to plants will lead to wilting and necrosis (Upadhyaya et al, 2013)
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