Analysis of the promoter region of the gene LIP1 encoding triglyceride lipase from Fusarium graminearum

Triglyceride lipases catalyze the reversible degradation of glycerol esters with long-chain fatty acids into fatty acids and glycerol. In silico analysis of 5′-end flanking sequence of the gene LIP1 encoding a triglyceride lipase from the wheat head blight pathogen Fusarium graminearum revealed the presence of several cis-regulatory elements. To delineate the function of these regulatory elements, we constructed a series of deletion mutants in the LIP1 promoter region fused to the open reading frame of a green fluorescent protein (GFP) and assayed the promoter activity. Analysis of GFP expression levels in mutants indicated that a 563-bp promoter sequence was sufficient to drive the expression of LIP1 and regulatory elements responsible for the gene induction were located within the 563–372 bp region. To further investigate the regulatory elements, putative cis-acting elements spanned within the 563–372 bp region were mutated using a targeted mutagenesis approach. A CCAAT box, a CreA binding site, and a fatty acid responsive element (FARE) were identified and confirmed to be required for the basal expression of LIP1, glucose suppression and fatty acid induction, respectively.