The characterisation of Late Embryogenesis Abundant 5 and Ethylene Responsive Factor 109 functions in plants growth and stress tolerance

Understanding plant responses to environmental stresses is a key strategy to meet the challenges of food security, adequate nutrition and sustainable agriculture. Environmental stresses limit plant growth and crop yields. In this thesis, the roles of Late Embryogenesis Abundant 5 (LEA5) and Ethylene Responsive Factor 109 (ERF109) in plant growth and stress tolerance were investigated. These two genes are involved in the regulation of plant redox processes. LEA5 was previously shown to provide tolerance to oxidative stress. Furthermore, previous studies using transgenic A. thaliana found that the over-expression of LEA5 resulted in plants with a greater biomass. However, the precise functions of LEA5 in these processes are unknown. In this thesis, genetic and protein interaction approaches were used to investigate the role of LEA5. Protein interaction studies, which used tandem affinity purification (TAP) of protein complexes combined with mass-spectrometry revealed several LEA5 interacting partners, including genes associated with stress tolerance. Transgenic crops provide a promising avenue to reduce yield losses, improve growth. Homozygous transgenic barley plants expressing LEA5 were found to have an altered shoot phenotype compared to WT barley plants. ERF109 is part of a regulatory network that has a major role in the adjustment of A. thaliana leaves to reach homeostasis after high-light stress. Understanding the roles of transcriptional regulatory networks and their effects on downstream target genes will aid in the development of stress tolerant crops. Phenotype analysis of erf109 mutants presented here suggest that ERF109 has a role in the control of shoot growth in the absence of stress. Moreover, protein interactions of ERF109 were elucidated using TAP, a number of which might explain the phenotypic characteristics of the erf109 mutants. Taken together, this information could be used in breeding programmes to improve the predictability and sustainability of crop yields by enhancing stress tolerance.