More severe and sustained droughts are a consequence of accelerating climate change and therefore they represent a pressing threat to global food security, especially in non-irrigated crops. Drought stress results in a significant reduction in photosynthetic efficiency, growth, and yield of staple crops such as rice. However, the extent of yield loss depends on many factors, among them the severity of drought stress and levels of crop tolerance. Studying the proteome rearrangement of different genotypes of rice upon the changing environmental cues leads to a better understanding of the molecular response of individual accessions of rice to water deficits. This thesis describes how different genotypes of rice respond to water deficit, using proteomic approaches.
To begin with, the proteomic response of eight genotypes of rice (Oryza sativa), including upland and lowland ecotypes, to drought stress was investigated. The results indicate a dynamic proteome response of each genotype to water stress, revealing how different genotypes are able to cope with drought stress by adaptive molecular changes in the major biological pathways. A global decrease in the abundance of photosynthesis-associated proteins was observed in all genotypes revealing the common response of all genotypes to water stress. This study enabled us to identify drought stress-responsive proteins in all varieties, regardless of their tolerance or intolerance to water stress, along with those specifically identified in one rice genotype but not the remaining genotypes.
In a further study, the changes in protein accumulation occurring in response to drought stress were investigated in three species of rice. These included the drought-sensitive genotype of Oryza sativa (O. sativa cv Nipponbare), the cultivated African rice Oryza glaberrima (O. glaberrima), and the drought resistant native Australian wild rice species Oryza australiensis (O. australiensis). The results of the quantitative proteomics analysis revealed a distinctive pattern of protein accumulation in O. australiensis that suggests that this species contains the largest repertoire of novel stress-responsive genes. Photosynthetic efficiency was less affected by water stress in O. australiensis, whereas it was distinctly impacted in O. sativa. Stress-response proteins were more abundant in water-stressed O. glaberrima than O. sativa, and were further enriched in O. australiensis.
To examine the impact of water stress in presence of varying nitrogen supply on protein phosphorylation, one of the important post-translational modifications, we performed a phosphoproteomic study on rice (O. sativa cv. Nipponbare). The peptides that belonged to membrane proteins, especially transporters, were the most significantly changed in phosphorylation. This suggests that the phosphorylation changes of transporter proteins may regulate water maintenance in leaf cells. Changing phosphorylation of peptides involved in RNA4 processing and carbohydrate metabolism upon varying water and nitrogen supply also suggested the role of phosphorylation in the regulation of signaling cascades in plant cells.
In summary, this thesis provides valuable insights into the molecular response of rice to drought at proteomic and phosphoproteomic levels, which includes the identification of new potential biomarkers for drought tolerance.
Table of Contents
Chapter 1. Introduction -- Chapter 2. Materials and methods -- Chapter 3. Proteomic responses to drought vary widely among eight diverse genotypes of rice (Oryza sativa) -- Chapter 4. Wild and cultivated species of rice have distinctive proteomic responses to Drought -- Chapter 5. The phosphoproteome of rice leaves responds to water and nitrogen supply -- Chapter 6. Characterisation of the physiological response of O. australiensis and a drought-sensitive O. sativa to water deficit and altered nitrogen supply -- Chapter 7. Conclusions and future directions -- Appendix I -- Appendix II -- Appendix III -- ReferencesAwarding Institution
Macquarie UniversityDegree Type
Thesis PhDDegree
Doctor of PhilosophyDepartment, Centre or School
Department of Molecular SciencesYear of Award
2021Principal Supervisor
Paul A. HaynesAdditional Supervisor 1
Brian AtwellRights
Copyright: The Author
Copyright disclaimer: https://www.mq.edu.au/copyright-disclaimerLanguage
EnglishExtent
195 pages
