Bennett Lab Research - Vascular Development

Vascular tissues are important conduits for movement of water, minerals and photoassimilates throughout the plant. Vascular tissues also provide mechanical strength to the plant. Wood is an important natural resource that provides essential raw materials for building and the paper industry. The structure and chemical properties of the pulp fibres are key determinants of the strength and properties of the end product. Formation of the secondary cell wall takes place within a defined region of the cambial tissue of trees and involves a large number of different enzymatic steps. Identification and characterisation of enzymes involved in secondary cell wall formation will help us to understand the chemistry and structure of wood fibres. This provides the potential for improvement of wood fibres through genetic engineering.

Currently the laboratory has funding from 2 EU framework V grants, POPWOOD and EDEN to perform a functional genomics based approach to identify key genes that regulate:

A large scale Expressed Sequence Tag (EST) programme in hybrid Poplar trees has initially identified 3000 individual gene sequences that are expressed within different tissues during development (Hertzberg et al., 2001; PopulusDB). Bioinformatic analysis of these sequences has demonstrated that a large proportion show high levels of homology to genes from other plant species including Arabidopsis thaliana. Transcript profiling of the Poplar ESTs within each of 5 developmentally distinct regions of the cambium has defined a subset which are highly expressed either within the zones of vascular differentiation or secondary cell wall formation. These differentially expressed genes provide candidates that may be important during wood formation. A reverse genetics approach in Arabidopsis is currently being employed to test the functional importance of these genes. Arabidopsis can be induced to undergo secondary cell wall thickening by growing plants under a defined temperature and light regime (Chaffey et al., 2002). This allows Arabidopsis to be utilised as a model for tree development while retaining the advantages of having a short life cycle and a fully sequenced genome, thereby allowing rapid phenotypic analysis of knockout mutants. This approach has yielded a number of interesting mutants to date which are currently being characterised. Genes demonstrating a likely function in secondary cell wall thickening in Arabidopsis will be manipulated in Poplar to determine the effect on fibre formation and properties.

References

Hertzberg, M., Aspeborg, H., Schrader, J., Andersson, A., Erlandsson, R., Blomqvist, K., Bhalerao, R., Uhln, Teeri, T., Lundeberg, J., Sundberg, B., Nilsson, P. and Sandberg, G. (2001) A transcriptional roadmap to wood formation. Proc. Natl. Acad. Sci. USA 98 14732-14737.