Dr David Hanke
Find out more about David Hanke and his Group or email David.Hanke@plantsci.cam.ac.uk
Project titles:
- Improving uniformity of potato crops
- Characterisation of Cytokinin-binding by plant proteins
- A novel signal molecule controlling plant resistance to viruses, fungi and bacteria, as well as to abiotic stresses
Project Title: Improving uniformity of potato crops
Supervisors: Dr David Hanke and Dr David Firman, The University Farm
This three year studentship is administered jointly by The Department of Plant Sciences and the Agronomy Group at The University Farm and is fully funded by the Cambridge University Potato Growers Research Association. Applications are welcomed from Home and EU students via the University Wide Admissions Process for entry to the Department in October 2011. The application deadline for this studentship is 14th January 2011. If you have any questions regarding the project, your eligibility or the application and admissions process please contact our Graduate Student Administrator in the first instance. To make an application please continue to the 'How to apply / make an application section.
Project outline:
Morphology of the potato plant both above and below ground is complex and variation within and between plants can have a significant effect on crop value. Variation associated with the formation and rate of growth of tubers can influence quality traits important for both fresh and processed crops including dry matter concentration and susceptibility to diseases (e.g. common scab) and defects (e.g. bruising). Despite the importance of such quality traits in determining the value of potato crops, in many cases the relationships between them and changes in uniformity that occur with crop development are unclear.
Our research group has advanced understanding of the process of tuber initiation and determination of tuber size distributions in field grown crops and this has contributed to the development of our crop models that are used for commercial applications. We are interested in establishing the role of environmental and genetic factors in influencing crop variation and are particularly concerned with quantifying seed and soil related factors that affect crop growth.
This project is expected to involve collecting detailed data on soil and other environmental variables and on individual tubers, plants and crops grown under contrasting conditions in both field experiments and commercial crops and is an opportunity to develop a broad range of skills in agronomy and data analysis. The outcome of the project should inform refinement of crop models and enable more efficient production of high quality potato crops.
See Research or
email: David.Hanke@plantsci.cam.ac.uk
Project Title: Characterisation of Cytokinin-binding by plant proteins
Supervisor: Dr David Hanke
Project outline:
The aim is to use novel techniques for analysing hormone binding, developed in the Group, to characterise cytokinin-binding by a range of different proteins recently isolated and sequenced by the Group.
We have isolated and sequenced four different putative cytokinin-binding proteins from potato stolon tips by affinity chromatography on cytokinin columns. All four are unrelated to each other, one of them is not related to proteins of known ‘function’, and one is closely related to the tomato homologue of a cytokinin-binding protein we isolated from cauliflower, and to a known tobacco cytokinin-binding protein.
To confirm that the isolated sequences encode cytokinin-binding proteins, we propose to express them, in vitro and in microorganisms, and test the products for cytokinin-binding activity. We shall use in vitro translation systems, expression vectors targeted to the periplasm in bacteria, and secretion vectors in Pichia.
To characterise binding, we will use equilibrium dialysis and two newly developed methods, both of which keep both binding entities in solution and therefore not kinetically compromised (cf. BIA-core, etc). One uses a miniature ultrafiltration probe, enabling us to monitor binding in small volumes (<500 µl) and over a time course, or a range of protein concentrations, for the same preparation. The second is called CARA for competitive antibody receptor assay, was patent registered and is ultra-sensitive.
In characterising binding we shall investigate affinity by Scatchard analysis, and specificity by competition experiments. The next step will be to identify residues close to the binding site by covalent labelling with radioactive azido-cytokinins, and to modify the sites by in vitro mutagenesis to confirm a role in binding. Once confirmed, we will search for homologous motifs, putative cytokinin-binding sites, in other expressed sequences. We have already pursued this strategy successfully for one of our four types of cytokinin-binding proteins.
References
- Hanke, D.E. (1999) Accentuate the positive and eliminate the negative. Current Opinion in Plant Biology 2, 423-425.
See Research or
email: David.Hanke@plantsci.cam.ac.uk
Project Title: A novel signal molecule controlling plant resistance to viruses, fungi and bacteria, as well as to abiotic stresses
Supervisors: Dr John Carr and Dr David Hanke
Project outline:
The sugar phosphate phytic acid (myo-inositol hexakisphosphate) is present in all plants and used in seeds and other storage tissues as a reserve for phosphate. Because phytic acid in the diet can have beneficial as well as deleterious influences on human health, and because the release of too much phytic acid in agricultural waste can exacerbate water pollution, various research groups have attempted to generate crop varieties with a modified content of phytate. While investigating lines of transgenic potato and Arabidopsis plants with decreased levels of phytate we serendipitously discovered that phytate is an important signalling molecule that regulates basal resistance to viral, bacterial and fungal pathogens of plants (Murphy et al., 2008) and influences the resistance of plants to abiotic stress (Otto et al., manuscript in preparation).
Arabidopsis has three a family of three genes encoding isoforms of the enzyme that catalyses the first step in the biosynthesis of phytate, the enzyme myo-inositol 3-phosphate synthase (AtIPS1–3). Plants with a mutation in the gene AtIPS2 (atips2 mutants) plants were hypersusceptible to the RNA viruses tobacco mosaic virus, turnip mosaic virus, cucumber mosaic virus and the DNA virus cauliflower mosaic virus, as well as to the fungus Botrytis cinerea and to the bacterial pathogen Pseudomonas syringae. In fact, these plants were as hypersusceptible to infection as plants unable to accumulate salicylic acid (SA), which is an indication of the importance of phytic acid in defensive signal transduction. In contrast, atips1 mutants were not hypersusceptible to pathogens but these mutant plants were more susceptible to abiotic stresses. Analysis of the promoter and protein-coding sequences of the AtIPS1 and AtIPS2 genes suggest that the two versions of IPS may be produced in different tissues of a plant and/or accumulate in different compartments within the plant cell. This suggests that different pools of phytate (occurring in different sub-cellular organelles or different plant tissues) may regulate separate signalling pathways regulating pathogen resistance (AtIPS2) or stress responses (AtIPS1). The aim of the project will be: to identify the sites of localization of AtIPS1 and AtIPS2, to identify a role for IPS3, and to determine whether or not the levels of phytate in plants can be altered without damaging a plant’s ability to combat pathogen infection or abiotic stress.
Reference
- Murphy, A.M., Otto, B., Brearley, C.A., Carr, J.P. & Hanke, D.E. (2008) A role for inositol hexakisphosphate in the maintenance of basal resistance to plant pathogens. Plant Journal in press
See David Hanke's Research or email: David.Hanke@plantsci.cam.ac.uk
See John Carr's Research or email John.Carr@plantsci.cam.ac.uk