Arbuscular Mycorrhiza: an ancient symbiosis in modern cereal crops
Food security is defined by FAO as the physical and economic access to food for all people at all times. On a global scale cereals provide 95% of the starchy staple food and are therefore of utmost importance for food security. Arbuscular Mycorrhizal (AM) symbioses first evolved >400 million years ago, whereas the domestication of crop plants began relatively recently, 10’000 years ago. The evolutionary history and taxonomic distribution of AM interactions suggest that the progenitors of our modern cereal crops inherited the capacity to interact with the corresponding beneficial fungi. To successfully tailor a complex biological interaction, such as an AM symbiosis, for agronomic application requires a level of understanding that exceeds what is currently available.
The establishment of an AM symbiosis proceeds as a series of genetically controlled steps. In our lab, we take genetic approaches in the cereals rice and maize to generate understanding about the molecular mechanisms underpinning the establishment and functioning of this important interaction. Projects are available for interested doctoral candidates across designing and performing novel genetic screens, cloning genes from available mutants, elucidating the role already known genes/factors play during symbiosis or translating findings made in the laboratory to the field.
We are specifically looking for interest in the following PhD projects:
(A) Mathematical modelling of phosphate uptake by the rice root system. BACKGROUND: Rice root systems are composed of three different root types (RTs) with distinct architectural and physiological properties. Crown roots (CRs) are sturdy to anchor the plant in the ground; they constitutively form aerenchyma, entirely lysing their cortex cell layers. Large Lateral Roots (LLRs) form on CRs and retain cortex tissue until ageing. Fine Lateral Roots (FLRs) develop on both CRs and LLRs. CRs can reach a diameter of >1mm, LLRs of ~370µm and FLRs of ~160µm and contribute to varying extend in the uptake of phosphate. Furthermore, CRs and LLRs engage with phosphate delivering arbuscular mycorrhizal fungi whereas FLRs do not. LITERATURE: Gutjahr, Casieri et al., New Phytol 2009; Gutjahr et al., Proc Natl Acad Sci 2015. PROJECT: The successful candidate will develop a mathematical model to represent and quantify the fluxes of phosphate across the three RTs in the presence and absence of the beneficial fungus. The student will be co-supervised by Dr. Uta Paszkowski (biological part) and Prof. Tiina Roose, University Southampton (mathematical part). REQUIREMENT: A prior education in mathematics, engineering or other numerate discipline is essential, experience in plant biology desirable.
(B) Functional conservation of cereal symbiosis genes in Marchantia paleacea. BACKGROUND: The Paszkowski group in recent years has identified a number of rice and maize genes required for establishment of the arbuscular mycorrhizal (AM) symbiosis (1-4). These genes are conserved in basal land plants such as liverworts. The liverworts Marchantia polymorpha has developed into a powerful model system for evo-devo approaches, and also for synthetic biology (www.openplant.com) but does not engage in beneficial interactions with AM fungi. In contrast, its relative Marchantia paleaceae becomes readily colonized and is amenable to genetic manipulations (5, 6). LITERATURE: (1) Gutjahr et al., Plant J 2012; (2) Yang et al., Plant Cell 2012; (3) Gutjahr et al., Science 2015; (4) Nadal et al., in preparation. (5) Ligrone et al., Am J Bot 2007; (6) Hata, Internat Review of Cell & Mol Biol 2010. PROJECT: The successful candidate will generate M. paleaceae mutants via the CRISPR/Cas9 technology to examine the phenotypic consequences of gene disruption on the interaction of this liverwort species with AM fungi. The student will acquire expertise in plant molecular biology, genetics, microscopy and physiology. A prior education in molecular biology is necessary, experience in plant sciences desirable.
Please consult our page 'how to apply' for eligibility and funding opportunities.