Project Outline

Elucidating the diversity and flexibility of plant metabolism is a key research avenue in the pursuit for malleable traits that can enhance plant productivity. Transient storage of carbohydrates in leaves is essential to maintaining metabolic processes through periods where photosynthesis is unavailable. Grass species are notable in that there is distinct variation in transient storage carbohydrates between grass species, with the most common composition being a species-specific combination of starch and sucrose. Variation in these transient starch/sucrose pools can be associated with both physiological and growth characteristics, due to the integral nature of both carbohydrates (Watson-Lazowski et al., 2022). In addition, there are incidental factors related to carbohydrate pools that link back to crop productivity, such as increased starch accumulation improving bioethanol production (Huang et al., 2020). Thus, identifying optimal transient carbohydrate ratios, associated with either species or environment, could represent an important avenue of crop improvement.

Phosphoglucoisomerase 1 (PGI1) and STARCH EXCESS 4 (SEX4) are two genes which are known to function in transient starch metabolism. PGI1 functions as an initial step in the starch synthesis pathway. Previous work using Arabidopsis thaliana showed pgi1 mutant lines are unable to synthesise starch throughout the day (Yu et al., 2000). On the other hand, SEX4 is a glucan phosphatase which is required for normal degradation of starch. Again using A. thaliana, previous work showed sex4 mutant lines gradually accumulate starch over time as degradation is impaired during the night (Niittylä et al., 2006). As A. thaliana innately transiently accumulates only starch, it is not suitable as a model to investigate phenotypes related to both starch and sucrose accumulation. However, wheat is not only a globally important crop species, as a grass, it transiently accumulates both starch and sucrose. By manipulating the carbohydrate pathways in wheat via mutations in the above genes, you will study how changes in transient allocation to each carbohydrate impacts plant functioning.

Using mutant lines generated within the Watson-Lazowski lab, your first objective will be to characterise and compare the metabolic phenotypes of sex4 and pgi1 mutants in wheat. Your second objective will then be to explore how these metabolic phenotypes effect plant functioning in response to abiotic stress. Finally, your third objective will be to assess how the metabolic phenotypes impact on additional desirable agronomic characteristics, such as insect herbivory resistance and animal silage properties. This work will utilise a range of genetic, biochemical and physiological techniques. To guide you, your supervisory panel will consist of experts in the fields of plant biology and entomology across Harper Adams University and the University of Birmingham.

Your PhD will take a multi-disciplinary approach to not only aid in the elucidation of transient carbohydrate pathways in wheat, but also show the possible benefits to desirable agronomic traits that can be achieved through the manipulation of transient carbohydrate pathways.

References

Huang et. al. (2020). Genetic engineering of transitory starch accumulation by knockdown of OsSEX4 in rice plants for enhanced bioethanol production. Biotechnology and Bioengineering, 117(4), 933-944.

Niittylä et. al. (2006). Similar protein phosphatases control starch metabolism in plants and glycogen metabolism in mammals. Journal of Biological Chemistry, 281(17), 11815-11818.

Yu et. al. (2000). Mutation of Arabidopsis plastid phosphoglucose isomerase affects leaf starch synthesis and floral initiation. Plant Physiology, 123(1), 319-326.

Watson-Lazowski et. al. (2022). Loss of PROTEIN TARGETING TO STARCH 2 has variable effects on starch synthesis across organs and species. Journal of Experimental Botany, 73(18), 6367-6379.

Techniques

• Genetic techniques – DNA/RNA extractions, PCR genotyping, RNA-Sequencing
• Biochemical techniques – Protein extractions, NAD/NADH assays, Western blots
• Physiological techniques – Photosynthetic measurements
• Entomology techniques – Insect monitoring and tracking