Comparative transcriptional analysis of caffeoyl-coenzyme A 3-O-methyltransferase from Hibiscus cannabinus L., during developmental stages in various tissues and stress regulation

Abstract

We have cloned a full-length gene, putatively encoding for caffeoyl-coenzyme A 3-O-methyltransferase (CCoAOMT), an important enzyme involved in lignin biosynthesis, from kenaf (Hibiscus cannabinus L.). Herein, we investigated the expression pattern of a CCoAOMT orthologue from various tissues and organs during development, and in response to different environmental cues. The full-length CCoAOMT orthologue of kenaf consists of a 744 bp open reading frame (ORF), encoding for 247 amino acids of 27.91 kDa and an isoelectric point (pI) of 5.43. The deduced amino acids of CCoAOMT evidenced a high degree of identity (up to 84%) with other plant CCoAOMT sequences. Phylogenetic analysis demonstrated its close relationship with the CCoAOMT of Gossypium hirsutum (ACQ59096). Kenaf CCoAOMT harbors eight highly conserved motifs: A, B, and C are putative S-adenosylmethioine (SAM)-binding motifs and D, E, F, G, and H are CCoAOMT signature motifs. According to quantitative real-time reverse transcriptase polymerase chain reaction (q-PCR) analysis, the kenaf CCoAOMT transcript was detected in all plant tissues and organs, whereas the highest expression was noted in mature flower tissues, which indicates that it might be involved in the flower development or in the biosynthesis of flower specific compound. All the treatments highly induced the expression of CCoAOMT transcripts in the stems of 3-week-old kenaf, which indicates that it might have a role in stress regulatory pathway. Among the treatments, the cold and H2O2-treated samples evidenced the highest levels of expression at 6 and 24 h after treatment, respectively, whereas the wounded and NaCl-treated samples evidenced lower expression levels, which suggest that different signaling networks are involved for stress mediated up regulation of HcCCoAOMT transcripts. The highest transcript level of CCoAOMT was detected at either early (within 12 h of treatments) or intermediate (24 h after treatments) time points of treatments, except drought treated sample. Early induction was observed in the case of H2O2 and SA (salicylic acid), and intermediate induction occurring as the result of wounding, NaCl, cold and ABA (abscisic acid). Whereas drought treated sample showed highest expression at seven days after treatment. MeJA (methyl jasmonic acid) treatment showed a complex biphasic expression which is different from others. In summary, we have cloned and characterized a full-length gene putatively encoding for CCoAOMT, which also showed stress responsive differential expression.