Expression kinetics of the quinic acid (qa) gene cluster in Neurospora crassa

Abstract

Eukaryotic genes are tightly regulated through a highly complex system with a number of checks and balances. When environmental conditions change, organisms need to adapt. Part of this reaction may be a shift in gene expression based on the regulation of that particular gene or gene cluster. The quinic acid (qa) gene cluster of Neurospora crassa is such a system. The up-regulation in gene expression for the qa cluster is triggered by the carbon source quinic acid. When the fungus is grown on quinic acid as a sole carbon source, the qa genes are expressed at high levels. However, when a preferred carbon source, such as dextrose, is used, the qa genes are repressed. This study will quantify the effects of changing carbon source over a three hour time period in the wild type strain of N. crassa, 74A. The focus of this study is the kinetics of induction of the various quinic acid genes as the environment changes. RNA was isolated from N. crassa grown under various conditions. Transcript levels of the various genes are detected by SYBR Green using quantitative reverse transcriptase polymerase chain reaction (qRT-PCR). Results are normalized to the internal control gene, 18s rRNA, and analyzed with Bio-Rad iQ5 software. These results reveal that the up-regulation in expression of the qa genes is detectable within 15 minutes of incubation with quinic acid and reaches peak levels, higher than previously thought, within 3 hours.