Calcium signaling positively regulates cellulase translation and secretion in a Clr-2-overexpressing, catabolically derepressed strain of Penicillium funiculosum.

backgroundLow-cost cellulase production is vital to sustainable second-generation biorefineries. The catabolically derepressed strain of Penicillium funiculosum NCIM1228 (PfMig1

resultsWe began by identifying the transcription factor responsible for cellulase production in NCIM1228. An advanced RNA-seq screen identified three genes, clr-2, ctf1a and ctf1b; the genes were cloned under their native promoters and transformed into NCIM1228. Of the three, clr-2 overexpression led to twofold higher cellulase production than the parent strain and was thus identified as the transcriptional activator of cellulase in NCIM1228. Next, we overexpressed clr-2 in ∆Mig1 and expected an exponential increase in cellulolytic attributes accredited to the reinforced activation mechanisms, conjoint with diminished negative regulation. Although clr-2 overexpression increased the transcript levels of cellulase genes in ∆Mig1, there was no increase in cellulase yield. Even a further increase in the transcript levels of clr-2 via a stronger promoter was ineffective. However, when the CaCO

conclusionsOur study identifies for the first time that cellulose activates two discrete signaling events to govern cellulase transcription and posttranscriptional processes (translation, processing and secretion) in P. funiculosum NCIM1228. Whereas Clr-2, the transcriptional activator of cellulase, governs transcription, calcium signaling specifically activates cellulase translation and secretion.