Characterization of a cinnamoyl-CoA reductase gene in <i>Ginkgo biloba</i>: Effects on lignification and environmental stresses

Abstract

Cinnamoyl-CoA reductase (CCR, EC 1.2.1.44) catalyzes key steps in the biosynthesis of monolignols, which serve as building blocks in the formation of plant lignin. The full-length cDNA of GbCCR is 1178 bp and contains a 972 bp open reading frame (ORF) encoding a 323 amino acid protein. The deduced GbCCR protein showed high identities with other plant CCRs, and had closer relationship with Picea abies, sharing 56.3% homology. They both contain a common signature which is thought to be involved in the catalytic site of CCR. Phylogenetic tree analysis revealed that GbCCR shared the same ancestor with other CCRs, but the divergence time is early. Southern blot analysis indicated that GbCCR belonged to a multi-gene family. The expression analysis by quantitative real-time polymerase chain reaction (QRT-PCR showed that GbCCR was seen in a tissue specific manner in Ginkgo biloba; it had the highest expression in injured stems, and a high expression in four years old stems, while it had the lowest in endosperm. GbCCR was also found to be significantly up-regulated by gibberellin (GA), but the expression was weakly induced by Agrobacterium treatment. QRT-PCR analysis showed that GbCCR activity correlated with changes in transcription level of the GbCCR gene, and GbCCR activity was also positively correlated with total lignin accumulation in developments of Ginkgo stem. In light of these properties and expression pattern, we suggested that the corresponding enzyme is probably involved in constitutive lignification and defense.

Key words: Ginkgo biloba L., GbCCR, gene expression, lignification, defense.