Doctor of Philosophy (PhD)


Department of Biological Sciences

Document Type



Investigating stress responses in plants is central to plant development studies and crop research. Identifying mechanisms of plant abiotic stress tolerance and adaptation will be keys to relieve the conflict between an increasing global population and declining agronomic land. Studies on extremophytes and their genetic responses to environmental stress are a way to help understand how and why these extremophile plants can develop well under extreme environments including high salinity and heavy metal toxicity. The studies herein first focus on comparative responses at the genetic level to lithium toxicity between Arabidopsis thaliana and Schrenkiella parvula. Based on elemental quantification with ICP-MS, Arabidopsis has a greater ability to translocate lithium from roots to shoots than S. parvula. Results of RNA-seq and GC-MS indicated that many biological processes of Arabidopsis are affected by lithium, including hormone signaling pathways, hormone biosynthesis pathways, and sugar content in roots. S. parvula, an extremophyte, appears able to maintain these biological processes in response to lithium as compared with Arabidopsis. Second, several rice cultivars were selected for further analysis based on preliminary findings that they have relatively high or low arsenic accumulation in their grain. ICP experiments revealed important differences in accumulation of total arsenic, inorganic arsenic, and organic arsenic. A candidate gene list was created according to previous QTLs related to arsenic accumulation and identified SNPs based on two rice cultivars showing extreme opposite traits of grain arsenic accumulation. These candidate genes may play an important role in the arsenic accumulation and tolerance differences observed in this study. Taken together, these findings will contribute to understanding how plants respond to lithium and arsenic, which can ultimately be used to enhance agricultural production and food safety.



Committee Chair

Smith, Aaron