Characterization of cinnamyl alcohol dehydrogenase gene family in lignifying tissues of Tectona grandis L.F.

Abstract

The cinnamyl alcohol dehydrogenase (CAD) enzyme catalyzes the last step of monolignols synthesis in the lignin pathway. Tectona grandis (teak) is a tropical tree with high valuable timber. As there is few genetic information about lignin formation in teak, the purpose of this study is to characterize members of CAD family in this species. As methodology, PCR amplification using cDNA samples, vector cloning, sequencing, bioinforma-tics analyses and gene expression studies using real time RT-qPCR were performed. As results, four members (TgCAD1-TgCAD4) were obtained. Comparative analyses showed that all of them have conserved residues for catalytic zinc action, structural zinc ligation, NADPH binding and substrate specificity, consistent with the mechanism of alcohol dehydrogenases. Phylogenetic analysis showed that TgCADs are present in three main classes and seven groups. Expression analyses revealed that TgCAD1 was highly expressed in leaves and could be related with pathogen defense. TgCAD2 was more expressed in branches and roots. Differently, TgCAD3 and TgCAD4 were highly expressed in juvenile and mature sapwood, suggesting a crucial role in wood development and lignin biosynthesis, with tissue-specialized expression profiles. Furthermore, TgCAD4 could be related with teak maturation for being more expressed in sapwood of mature teak trees. As conclusion, this work is the first to characterize genes of CAD family in Tectona grandis. These genes could be interesting to develop transgenic plants for basic research and field applications.