Epsilon Open Archive

Abstract

The formation of secondary vascular tissues involves complex processes and many steps, a number of which have been examined in detail in this study. A novel CuZn-SOD, with a high pI and thus denoted hipI-SOD, was identified and characterized in Pinus sylvestris. Results from immunolocalisation analyses indicated that it is localised in lignified structures, suggesting that SOD might participate in the formation of secondary cell walls and lignification. To further investigate its role in these processes, a Zinnia mesophyll cell system was set up. This enabled us to follow the differentiation from mesophyll cell to tracheary element. Various inhibitors against SOD and H2O2-production were applied. The results suggested that HipI-SOD might have a novel and important function in secondary cell wall formation and lignification processes. The expression pattern and localization of the protein during formation of tracheary elements support this assumption. The other part of this study involved analysis of transcription factors and their regulation, especially in secondary vascular tissues. The genes encoding three MYB-transcription factors and one novel Zinc-finger transcription factor were found in an EST-library from the cambial region of hybrid aspen (Populus tremula L. x tremuloides Michx.). The genes were cloned and characterized and their regulation by hormones, sucrose and gravity was investigated. The genes were found to be under hormone and sucrose control, and their expression altered during tension wood formation. Transgenic plants were constructed, carrying one of two antisense constructs of MYB-genes, PttMYB46 or PttMYB76, which were strongly expressed in lignified tissues. Analysis of plants with either of these constructs displayed a complex phenotype, including reduced growth, increased concentration of some phenolic acids and changes in lignin composition. Some of the phenotypic traits were indicative of strong investment in defensive characters.