REGULATION OF THE YEAST SPS19 GENE ENCODING PEROXISOMAL 2,4-DIENOYL-COA REDUCTASE BY THE TRANSCRIPTION FACTORS PIP2P AND OAF1P - BETA-OXIDATION IS DISPENSABLE FOR SACCHAROMYCES-CEREVISIAE SPORULATION IN ACETATE MEDIUM

The yeast SPS19 gene encoding the peroxisomally targeted 5,4-dienoyl-C oA reductase shares its promoter region (291 bp) with the sporulation- specific gene SPS18. SPS19 is induced during sporulation in diploids b ut to a lesser extent than SPS18; under oleate induction conditions, S PSI9 but not SPS18, is transcribed via an oleate response element (ORE ) independently of ploidy or sporulation. The SPS19 ORE is the binding target of the Pip2p and Oaf1p transcription factors, and an SPS19-lac Z reporter gene, which is highly expressed in oleate-induced cells, is not activated in haploids devoid of either protein. We examined the e xpression of CYC1-lacZ reporter constructs carrying the SPSIS and CTA1 OREs in diploids propagated under sporulation conditions and have sho wn that OREs are not sufficient for heterologous expression during yea st development, In addition, diploids deleted at either PIP2 or OAF1 d emonstrated abundant ascosporogenesis, indicating that these genes are not essential for sporulation, A Delta pex6 strain lacking peroxisoma l structures and one devoid of fatty acyl-CoA oxidase (Delta pox1), th e first step in fungal beta-oxidation, were both proficient for sporul ation and, hence, beta-oxidation and the peroxisomal compartment conta ining it are dispensable for meiotic development.