Effect of bis (2-ethylhexyl) phthalate on Tetrahymena thermophila DCL-1 Gene Expression and Conjugation

Abstract

Phthalates, often referred to as plasticizers, are a group of chemicals used in hundreds of products including detergents, food packaging, and nail polish. Bis (2-ethylhexyl) phthalates (DEHP) have recently been shown to disrupt endocrine chemical balances, thereby causing reproductive strain. For this project, we wanted to explore how DEHP influences conjugation in Tetrahymena thermophila and to determine how DEHP exposure affects expression of the DCL-1 gene. The DCL-1 gene encodes the protein DCL-1 which is essential for transmitting genetic information during the process of conjugation in T. thermophila. We hypothesized that DEHP will act as a repressor of conjugation resulting in a decrease in expression of the DCL-1 gene and a decrease in reproduction rates. To test our hypothesis, control and experimental T. thermophila were cultured in starvation media in order to induce conjugation. The media for the experimental cells was supplemented with 0.1 µM DEHP, a toxic dose concentration that aligns with previous studies. The cultures were maintained in their respective media for 12 hours and conjugation of the T. thermophila was measured every 3 hours. Immediately following the 12 hour exposure, the control and experimental cultures underwent RNA extraction and gene-specific Reverse Transcription - quantitative Polymerase Chain Reaction (RT-PCR) to measure expression of DCL-1. Exposure of T. thermophila to DEHP was predicted to decrease conjugation and decrease DCL-1 expression as a consequence of phthalate toxicity.