The Role of the MATE45 Transporter in the Abiotic Stress Response of Arabidopsis thaliana

A plant's healthy growth and development is dependent on the plant's ability to transport its metabolites to the location where they carry out their function. These metabolites include hormones, which have a large role in the growth and development of the plant in normal conditions and also in conditions of abiotic stress. For example, abscisic acid (ABA) is a hormone that has a role in drought and salt stress, by inducing the genes that encode the dehydration tolerance proteins and ion channel proteins that are involved in changing the guard cell shape that leads to stomata closure. This thesis focuses on the role of a specific Multidrug and Toxic Compound Extrusion (MATE) transporter, MATE45, which we found has a role in the ABA pathway in Arabidopsis thaliana. mate45-1 is a mutant of MATE45 with a T-DNA insertion, which lead to an overexpressed transcript of the gene, but created a truncated gene product. Seedlings of mate45-1 grown in anthocyanin induction condition (AIC; 3% sucrose in water) stress showed a failure to arrest growth phenotype that was recessive. The WT phenotype was rescued in mate45-1 when a functional copy of MATE45 was inserted. This allowed us to confirm that the mate45-1 phenotype we observed was indeed due to a mutation in the MATE45 gene. The mate45-1 phenotype was similar to that of a plant in which the MATE45 gene had been silenced. This indicated that the truncation of the mate45-1 mutant gene made a product that had reduced function, similar to the scenario where the transporter was being silenced. The mate45-1 phenotype was not dependent on the presence or absence of anthocyanins in the plant, but was dependent on ABA. Overall, this showed that MATE45 did indeed have a role in the plant’s response to abiotic stress, which affected the ABA pathway.