A homeobox protein Phx1 regulates long-term survival and meiotic sporulation in Schizosaccharomyces pombe
1 Laboratory of Molecular Microbiology, School of Biological Sciences, and Institute of Microbiology, Seoul National University, Seoul, 151-742, South Korea
2 Program in Gene Function and Expression, University of Massachusetts Medical School, Worcester, MA, 01605, USA
BMC Microbiology 2012, 12:86 doi:10.1186/1471-2180-12-86Published: 30 May 2012
In the fission yeast Schizosaccharomyces pombe, the phx1+ (
Fluorescence from the Phx1-GFP expressed from a chromosomal fusion gene demonstrated that it is localized primarily in the nucleus, and is distinctly visible during the stationary phase. When we replaced the N-terminal homeobox domain of Phx1 with the DNA binding domain of Pap1, a well-characterized transcription factor, the chimeric protein caused the elevation of transcripts from Pap1-dependent genes such as ctt1+ and trr1+, suggesting that Phx1 possesses transcriptional activating activity when bound to DNA. The amount of phx1+ transcripts sharply increased as cells entered the stationary phase and was maintained at high level throughout the stationary phase. Nutrient shift down to low nitrogen or carbon sources caused phx1+ induction during the exponential phase, suggesting that cells need Phx1 for maintenance function during nutrient starvation. The Δphx1 null mutant showed decreased viability in long-term culture, whereas overproduction of Phx1 increased viability. Decrease in long-term survival was also observed for Δphx1 under N- or C-starved conditions. In addition, Δphx1 mutant was more sensitive to various oxidants and heat shock. When we examined sporulation of the Δphx1/Δphx1 diploid strain, significant decrease in the formation of meiotic spores was observed.
Phx1 is a transcriptional regulator whose synthesis is elevated during stationary phase and by nutrient starvation in S. pombe. It supports long-term survival and stress tolerance against oxidation and heat, and plays a key role in the formation of meiotic spores.