Performing Department
(N/A)
Non Technical Summary
Drought and salinity stress are the major abiotic stresses limiting crop productivity worldwide. Furthermore, climate change and rising sea levels will exacerbate the effects of water scarcity and soil salinity on crop productivity. There is therefore a need to better understand the mechanisms that control drought and salt tolerance, particularly in cereal crops that are the foundation of our food supply. In this project, the role the plant hormone cytokinin plays in regulating resistance to drought and salt stress will be characterized. The studies will be performed in rice, which is an important crop worldwide, and which shares similar characteristics with other cereal crops. The experimental focus will be to test the hypothesis that cytokinin plays a positive role in mediating resistance to drought and salt stress in rice, particularly at the reproductive stage of growth that is key to grain yield. The role of cytokinin will be evaluated by generating and characterizing mutants that alter the cytokinin response, a prediction being that mutants with an enhanced cytokinin response will also demonstrate enhanced resistance to drought and salt stress. The results from this project will form a basis for improving plant productivity through foundational studies on abiotic stress, with the information obtained from rice having significance for other agronomically important crops such as maize, wheat, barley, rye, and sorghum.
Animal Health Component
0%
Research Effort Categories
Basic
100%
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
The overall goal of this project is to determine the role that cytokinin plays in regulating drought and salt stress responses in rice, with a particular focus on developing cytokinin-based strategies to alleviate these abiotic stresses in crops. For this purpose, we will take a mutant-based approach, taking advantage of lines we have generated in rice that confer hypo- and hyper-sensitivity to cytokinin. Our Aims are as follows:Aim 1. Generation and characterization of cytokinin hypersensitive lines. We hypothesize that loss-of-function lines of the KMD and type-A RR families will result in varying degrees of cytokinin hypersensitivity. We will therefore complete the generation of mutant lines in these gene families by employing a CRISPR-Cas9-based approach, and characterize the effects of these mutations on growth and development as well as on cytokinin sensitivity using physiological and molecular assays.Aim 2. Determine the roles cytokinin signaling plays in the drought and salt stress responses. We will test the hypothesis that increased cytokinin sensitivity will confer increased resistance to abiotic stresses in rice. For this purpose, we will characterize cytokinin hypo- and hypersensitive mutant lines for their sensitivity to drought and salt stress at seedling, pre-anthesis, and post-anthesis growth stages in rice, making use of physiological, biochemical, and molecular assays.Aim 3. Identify gene regulatory networks by which cytokinin mediates drought and salt stress resistance We hypothesize that cytokinin initiates drought-stress specific, salt-stress specific, and co-response pathways. We will test this hypothesis by performing RNA-seq analysis using our stress-resistant mutant lines, comparing their response to the wild type and to each other, and generating networks to uncover individual and co-responsive pathways. Results will suggest potential mechanisms by which cytokinin modulates these abiotic stress responses.
Project Methods
The overall goal of this project is to determine the role that cytokinin plays in regulating drought and salt stress responses in rice, with a particular focus on developing cytokinin-based strategies to alleviate these abiotic stresses in crops. For this purpose, we will take a mutant-based approach, taking advantage of lines that confer hypo- and hyper-sensitivity to cytokinin.For the generation of cytokinin hypersensitive lines, we will employ a CRISPR-Cas9-based approach to generate loss-of-function mutants involving the KMD and type-A RR families of rice. The effects of these mutations on growth and development will be determined based on root system architecture, plant height, tillers per plant, flag leaf length and width, stomatal density, panicle architecture, and seed set. The effect of these mutations on cytokinin sensitivity will be determined based root growth and dark-induced senescence responses to cytokinin, as well as on the induction of cytokinin primary-response genes.To determine the roles cytokinin signaling plays in the drought and salt stress responses, we will characterize cytokinin hypo- and hypersensitive mutant lines for their sensitivity to drought and salt stress at seedling, pre-anthesis, and post-anthesis growth stages in rice. The drought stress response will be characterized based on physiological (photosynthetic parameters, seed set, relative water content of the leaf), biochemical (proline and sugar levels, chlorophyll levels), and molecular assays for genes regulated in response to drought stress. Some of these same assays will be employed to examine the salt stress response, due to the ability of salt to induce a drought stress response. In addition, the salt stress response will be characterized based on its ion specificity, ICP analysis to determine levels of Na+ and K+ in the root and shoot, and molecular assays for genes regulated in response to salt stress.To identify gene regulatory networks by which cytokinin mediates drought and salt stress resistance, we will perform RNA-seq analysis using our stress-resistant mutant lines, comparing their response to the wild type and to each other, and generating networks to uncover individual and co-responsive pathways.Results from these studies will be communicated to the audiences by publication in scientific journals, by press releases alerting audiences to these publications, and by presentations at scientific conferences. Success of the project will be assessed by the collection and analysis of the data described above, each of which will generate quantifiable results, and by publication of results in peer-reviewed scientific journals.