Regulation of xyn3 gene expression in Trichoderma reesei PC-3-7

Abstract

The characteristics of regulation of the gene encoding the third xylanase (Xyn III) of a filamentous fungus, Trichoderma reesei PC-3-7, were studied by Northern blot analysis. A partial DNA sequence (185 bp) of the xyn3 gene was obtained by PCR amplification of genomic DNA of T. reesei PC-3-7 and sequenced. This xyn3 gene fragment was used as a probe for Southern and Northern blot analysis. The expression of the xyn3 gene was regulated at the transcriptional level. The xyn3 mRNA was expressed in mycelia of T. reesei PC-3-7 induced by Avicel, L-sorbose and sophorose, but not by xylose, xylooligosaccharides and birchwood xylan. Furthermore, it was observed that xyn3 was synchronously expressed with egll but not with xyn1 and xyn2 by L-sorbose, indicating that the xyn3 gene may be coordinately expressed with cellulase genes. By Southern blot analysis, the xyn3 gene was confirmed to exist as a single copy in both strains of T. reesei PC-3-7 and QM9414. However, no xyn3 mRNA appeared in the mycelia induced by any kind of inducers in T. reesei QM9414 even when total RNA was used in large excess, suggesting that the xyn3 gene in T. reesei QM9414 is in the dormant state and cannot be expressed. Therefore, T. reesei PC-3-7 may be a very useful strain for elucidating the induction mechanism of xylanase biosynthesis by cellulosic and xylanosic substrates, and also the regulatory correlation between cellulase and xylanase induction.

Assessment of the Effect of Easily-metabolised Carbon Supplements on Xylanase Production by Newly Isolated Trichoderma asperellum USM SD4 Cultivated on Oil Palm Empty Fruit Bunches

“…Probable xylanase inducers are xylobiose, L-arabinose, and cellulose. Others are lactose, which is often used in the industries for the production of hydrolytic enzymes, and sophorose, which was reported as the most powerful xylanase inducer (Chaudhuri and Sahai 1994;Xu et al 2000;Xiong et al 2004). Possible explanations for these contrasting observations could be differences in the physiological and metabolic properties of the various organisms used, the type of fermentation (SSF or SMF), or more importantly, the composition of the fermentation media including the carbon sources (soluble carbon or lignocellulosic sources) (Kulkarni et al 1999).…”

Identification of Major Facilitator Transporters Involved in Cellulase Production during Lactose Culture ofTrichoderma reeseiPC-3-7

“…The PC-3-7 strain, which exhibits increased cellulase activity under inducing conditions, has been used as a model of cellulase induction in our laboratory. [20][21][22] This mutant was developed following several rounds of random mutagenesis. 23,24) During screening for hyper-cellulolytic strains, we found that this strain exhibited an absence of carbon catabolite repression, and that it produced high amounts of cellulases during induction by cellulose, sophorose, and the monosaccharide L-sorbose.…”

Xylanase Gene Transcription in Trichoderma reesei Is Triggered by Different Inducers Representing Different Hemicellulosic Pentose Polymers

“…While the cellulases of T. reesei are known to be coordinately regulated by cellulose, lactose, and the ␤-1,2-diglucoside sophorose (8,9), differences in the induction of the xylanases were reported: expression of xyn1 is induced by Dxylose, whereas expression of xyn2 is induced by xylobiose and the cellulase-inducing carbohydrates cellulose and sophorose (10). xyn3 expression was found only in a mutant strain (T. reesei PC-3-7) and was induced only by cellulase inducers and not by D-xylose (11). No data on the expression of xyn4 are available.…”