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Abstract In order to obtain the full-length sequence of polyphenol oxidase gene (PPO) and its expression in different tissues, it was cloned from lotus rhizome (Nelumbo nucifera Gaertn. ssp. nucifera) bud by using RACE technique. The full length cDNA of PPO was 2 074 bp with open reading frame 1 503 bp, encoding a protein of 501 amino acids, 5'UTRs of 160 bp and 3'UTRs of 411 bp (GenBank No. HQ380894). Bioinformatics analysis showed that the molecular weight of PPO gene was 56.8 kD with pI value 8.60, which had tryosinase family domain, hydrophilic characteristics and trans-membrane properties but no signal peptide. Both α-helix and β-turn were found spreading in the whole polypeptide chain. The expression of PPO gene in five lotus tissues (rhizome bud, young leaf, petal, fresh rhizome cut and stem) was also investigated and the variance analysis results showed that the relative expression level of PPO in rhizome bud was only slightly higher than that in young leaf, but significantly higher than those in the other three tissues. The expression level in young leaf was no difference with that in fresh rhizome cut, but significantly higher than both in petal and stem. The expression levels in petal and stem were lowest and no significance between them. These results indicate that PPO gene produced in rhizome bud (an important meristem) may have no activity or be unstable, which is distributed to different tissues after production accompanying with organ development and responsible for corresponding functions under specific spatial and temporal conditions.
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Received: 09 November 2010
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