Determination of selenium (Se) toxicity tolerance genes in European alkali grass (Puccinellia distans)

Abiotic stresses such as metal/metalloid toxicity negatively impact plant growth and development. Selenium (Se), a metalloid, is essential for humans and animals, but excessive amounts of Se can cause toxicity in all organisms, including plants. The identification of mechanisms that tolerance to metal/metalloid factors plant species that are hyperaccumulators often used. In this study, Puccinellia distans, an accumulator species of boron and selenium, is known to have multi-tolerance to stress factors such as drought and salinity. While transcriptomic studies have attempted to shed light on Se tolerance mechanisms, the genes involved in this mechanism have not been clearly identified. To identify Se tolerance genes, the existing P. distans cDNA library was screened with yeast cells against toxic levels (15 mM) of selenium. As a result of the screening, two different genes that showed tolerance to toxic levels of selenium were identified in the root and leaf cDNA libraries, respectively, and were named PKS1 and PYS9.1. After sequencing, PKS1 was determined to be Thiocyanate methyltransferase 2, and PYS9.1 was determined to be Zinc Transporter 8. Colonies carrying the Zinc Transporter 8 gene were found to be able to tolerate up to 15 mM sodium selenite on YNB medium, while yeast cells carrying the Thiocyanate methyltransferase 2 gene were found to be able to tolerate up to 50 mM sodium selenite. The tolerance of P. distans " Thiocyanate methyltransferase 2" and "Zinc Transporter 8" genes to salt and drought stress was also investigated using yeast cells carrying these genes. However, due to its ability to provide tolerance to high concentrations of selenium, the characterization of the Thiocyanate methyltransferase 2 gene was not carried out in this study. Future studies on the functional characterization of these genes in plant cells and their roles in the Se tolerance mechanism will contribute to the development of plant species with increased tolerance to metal/metalloid toxicity and other abiotic stresses.