Assistant Professor of Biology Metropolitan State University Saint Paul, Minnesota
Body of Abstract: The cysteine-rich protein Cadmium Tolerance1 (CDT1) has been described in multiple monocots including Oryza sativa (rice) and Digitaria ciliaris (crabgrass). Five homologs of this gene exist in rice, one of which, OsCDT3, was found to confer aluminum tolerance instead of cadmium tolerance. Though CDT1 is commonly found in the genomes of dicots, nothing is known about the role of CDT1 in these plants. Arabidopsis thaliana CDT1 (At1g52927) is a single-copy gene. We found that expression of AtCDT1 in roots of Col-0 seedlings did not increase in response to cadmium or aluminum stress. The short length of the CDT1 protein (49 AAs in Arabidopsis) makes reverse-genetic characterization challenging, as few T-DNA lines are available. Arabidopsis seedlings carrying a T-DNA insertion mutation in the AtCDT1 promoter do not have an altered phenotype compared to Col-0 in growth across a range of pH treatments, nor under cadmium stress or aluminum treatment. Interestingly, the promoter insertion mutants overexpress AtCDT1 in control and metal-stress conditions, even while showing no abnormal stress response. Recently, we have generated plants carrying CRISPR-induced indel mutations within the AtCDT1 promoter and/or Exon 1 regions. Characterization of mutations within the AtCDT1 sequence, as well as gene expression analysis, is ongoing. Growth and stress-responsive phenotypes of these new cdt1 mutant plants, along with CDT1prom-GFP reporter lines, will help elucidate this gene's potential function within dicot plants in tolerance to aluminum alone, cadmium alone, both, or neither of the metals. This work has been done solely by undergraduate research students, nine of whom have worked on the project (so far!) to varying degrees.