WHIRLY Protein Functions in Plant Development

All plants have at least two WHIRLY (WHY) proteins that are localised to organelles and the nucleus. Arabidopsis has an extra WHY3 protein. WHY proteins have multiple functions in plant growth and defence, including photosynthesis and stress tolerance. The studies reported here were designed to explore the roles of WHY1 and WHY3 in seed viability, germination, and later development of Arabidopsis including flowering timing. The Arabidopsis Atwhy1, Atwhy3 and Atwhy1why3 mutant lines were first analysed and then this data was used to inform studies in wheat with RNAi Tawhy knockdown lines. Germination was similar in all the mutant lines compared to the wild type Arabidopsis. However seed ageing studies revealed a significant reduction in seed viability in the Atwhy1why3 seeds. Furthermore, analysis of RNA-seq data revealed significant differences in the transcriptome profiles of the Atwhy1why3 seeds compared to WT. In particular, transcripts encoding heat shock response and drought response related proteins were changed in abundance. Other transcripts indicate changes in phytohormone signalling particularly involving abscisic acid (ABA). Furthermore, at the later stages of plant development the Atwhy1why3 mutants had reduced biomass, fewer leaves and lower chlorophyll contents than the WT. Wheat mutants lacking WHY1 had a delay in flowering timing compared to the wild type. These data show that WHY proteins have important functions in seeds and in plant development. The findings reported in this thesis thus have wider implications for future food security in crops, particularly in relation to environmental change.