dr. sc. Snjezana Mihaljevic

Rudjer Boskovic

New transcription factors involved in the regulation of lignin biosynthesis

Xylogenesis (in trees known as wood formation) is characterized by the terminal cell differentiation and deposition of lignins within the secondary cell walls. Considering the biological and economical importance of lignins, numerous research efforts have been directed towards the improvement of lignin profiles in commercially important tree and crop species. The group of Jacqueline Grima-Pettenati (UMR CNRS-UPS 5546, Pôle de Biotechnologie Végétale, Castanet Tolosan) has a continual interest in understanding the regulation of xylem differentiation. Two Myb transcription factors, EgMyb1 and EgMyb2, expressed in xylem tissue have been cloned from Eucalyptus gunni cDNA library. The corresponding recombinant proteins recognize specific Myb binding sites in the promoter regions of both cinnamoyl-CoA reductase (CCR) and cinnamyl alcohol dehydrogenase (CAD) genes. In transient expression assays Myb1 acts as a negative regulator and Myb2 as an activator of lignifications genes. Transformation experiments in tobacco with sense Myb1 and Myb2 constructs result in transgenic plants with an increased lignin content and thickened cell wall in the case of Myb2 over expression. Results indicate that ectopic expression of transcription factors induce major changes in the expression of lignification genes.