Regulation of cell division during plant vascular development

Wood is used for a variety of products from pulp and paper to building material. Wood is essentially composed of specialised plant cell walls. Woody tissue is found in a variety of plants in addition to trees and is mostly made of sugars bonded together into long and sometimes complex polymers. It has also recently been suggested that if we could release these sugars efficiently it might be possible to make the next generation of biofuels or process wood to form a variety of different chemicals. Increasing world population and affluence has led to increased demand for food and to ensure that the demand for non-food based plant material does not impinge of food production it is necessary to find ways to increase woody tissue production. The long generation time of trees make it impractical for any studies that involve breeding, however, it is possible to use a small weed known as Arabidopsis to study many of the same processes that regulate wood formation in trees. We are able to undertake many experiments in Arabidopsis relatively quickly and identify the mechanisms that regulate the formation of woody tissue in Arabidopsis. We can then use this information to test if the same mechanisms work in trees. So far we have been able to identify genes in Arabidopsis that regulate woody tissue formation and these same genes are sufficient to increase wood formation in trees suggesting that the mechanism is conserved. We have also used Arabidopsis to identify two transcription factors that appear to be involved in regulating the division of wood forming cells. Transcription factors are proteins that turn on or off many other genes and in this case altering the levels of these transcription factors can alter the amount of woody tissue, but has many other undesirable affects. We will use Arabidopsis to identify which genes these transcription factors bind to. We will then test to what extent the so-called 'downstream genes' are specifically able to increase the amount of woody tissue formed. Once we have established which genes are able to do this in Arabidopsis, we will test for the ability of these genes to increase wood formation in trees.

Plant secondary cell walls constitute the majority of plant biomass and most secondary cell walls are found in the xylem that is generated from vascular meristems. While vascular meristems are most obvious in trees where they are responsible for radial expansion through secondary growth, they are also an important part of Arabidopsis development, where secondary growth occurs during hypocotyl development. A very similar process occurs in the procambium during vascular development in the stem. We have identified the receptor kinase PXY and its ligand the short peptide (CLE41) that define a multifunctional pathway that is essential for regulating the rate and orientation of vascular cell division as well as inhibiting xylem cell differentiation. We have manipulated the expression of PXY and CLE41 to make dramatic increases in the amount of vascular tissue in Arabidopsis. Furthermore, we have been able to use the Arabidopsis genes to increase the amount of vascular tissue in both Tobacco and Poplar suggesting that the pathway is highly conserved between distant species. More recently we have identified that ethylene also regulates cell division in the cambium via a pathway that results in the upregulation of a group of ERF/AP2 transcription factors. Altering the expression of these genes, however, has a number of pleiotrophic affects in addition to regulating vascular cell divisions. We will use a combination of expression analysis and chromatin immunoprecipitation to identify the direct targets of these ERFs and analyse the function of these target genes during vascular development. This information will be used to identify the regulatory network underlying vascular cell division. We will determine to what extent this network is conserved in the model tree Poplar. Using this information we will determine what extent we are able to increase vascular tissue development in both Arabidopsis and Poplar without having a detrimental affect on other aspects of plant growth.

Plant cell walls are at the heart of any sustainable biofuels programme. Biomass is essentially plant cell wall material and the potential yields and gains are very large if we are able to utilise it efficiently. With the ambitious targets that have been set for generating fuel from renewable resources and increasing pressure from population growth, there is likely to be a huge demand for plant biomass. Secondary cell walls in xylem cells are the biggest source of biomass. Ultimately, this programme will be of potential use to anyone with an interest in efficiently utilising biomass. This will include companies interested in generating the material (seed/plant suppliers) as well as those interested in processing it such as the pulp and paper industry or using it directly as forage crops. Any opportunities for commercial exploitation will be explored using the Universities commercial arm (UMIP). They will deal with the patenting of any discovery and negotiating any licensing agreements with commercial parties. Patents will be drawn up by an independent patent attorney with input from members of UMIP staff, the PI and the RA. They will also help in applying for any follow on funds that are necessary. We are currently in the final stages of negotiating a licence with a Swedish biotechnology company, on a patent. The PI has had a long standing relationship with this company and the negotiations were started on the basis of personal contacts. The PI is well connected to a number of labs and industries across Europe via the EU FP7 programme, composed of 15 partners, focused on optimisation of plant biomass. In addition to personal contacts, UMIP will also undertake to market any patents through their own list of worldwide contacts. They will be responsible for generating summaries of the discoveries as well as distributing and marketing this information. The work will be disseminated to the wider community by the normal channels. Papers on any discoveries will be published in the scientific literature. With the help of the PI, the RA will be encouraged to write reviews and articles to publicise the work and to promote interest in the wider scientific area of research into plant vascular development and biomass as he has done already (e.g. review on 'lateral meristems' for Encyclopedia of Life Sciences (ELS)). The work will be disseminated to the wider community through a variety of means. High school students will be encouraged to visit the lab as part of their work experience. The RA and PI will write magazine articles such as the biological sciences review, that are aimed at sixth form school children. Members of the Turner lab have engaged with local schools by visiting a local primary school and talking about this area of work and by giving demonstrations in local museums, the RA employed on this project will be encouraged to carry out similar work.