Comparison and characterization of α-amylase inducers in Aspergillus nidulans based on nuclear localization of AmyR

Abstract

AmyR, a fungal transcriptional activator responsible for induction of amylolytic genes in Aspergillus nidulans, localizes to the nucleus in response to the physiological inducer isomaltose. Maltose, kojibiose, and d-glucose were also found to trigger the nuclear localization of GFP-AmyR. Isomaltose- and kojibiose-triggered nuclear localization was not inhibited by the glucosidase inhibitor, castanospermine, while maltose-triggered localization was inhibited. Thus, maltose itself does not appear to be an direct inducer, but its degraded or transglycosylated product does. Non-metabolizable d-glucose analogues were also able to trigger the nuclear localization, implying that these sugars, except maltose, directly function as the inducers of AmyR nuclear entry. The inducing activity of d-glucose was 4 orders-of-magnitude weaker compared with isomaltose. Although d-glucose has the ability to induce α-amylase production, this activity would generally be masked by CreA-dependent carbon catabolite repression. Significant induction of α-amylase by d-glucose was observed in creA-defective A. nidulans.

Distinct mechanism of activation of two transcription factors, AmyR and MalR, involved in amylolytic enzyme production in Aspergillus oryzae

“…In A. nidulans, the transglycosylation activity of two α-glucosidases (AgdA and AgdB) with a signal peptide is involved in the conversion from maltose to isomaltose for α-amylase gene induction, although other α-glucosidase(s) with isomaltose-forming activity may exist (Kato et al 2002a, b). The nuclear localization of A. nidulans GFP-AmyR after maltose addition was inhibited by the addition of a α-glucosidase inhibitor, castanospermine (Murakoshi et al 2012). However, in A. oryzae, induction of α-amylase gene expression after maltose addition was not inhibited by the addition of α-glucosidase inhibitors, castanospermine and 1-deoxynojirimycin (data not shown).…”

“…2c). These results suggested that inducing sugars, such as maltose and glucose, for amylolytic gene expression can trigger the nuclear localization of AmyR in A. oryzae, as observed for AmyR in A. nidulans (Makita et al 2009;Murakoshi et al 2012). On the contrary, GFP fluorescence was observed in the nucleus when the transformant expressing GFP-MalR was cultured in the liquid MM using casamino acids as the carbon source (Fig.…”

“…Although the expression of amylolytic genes is strongly repressed by a C 2 H 2 -type transcription factor, CreA, under glucose-containing condition, the nuclear localization of GFP-AmyR is also triggered by glucose. However, glucose and maltose require higher concentration and longer time, when compared with isomaltose, to induce nuclear localization of GFP-AmyR (Murakoshi et al 2012). These observations indicate that isomaltose is the strongest inducer for the activation of A. nidulans AmyR.…”

Regulators of plant biomass degradation in ascomycetous fungi

“…A direct effect has been reported for xlnR/xyr1 in A. nidulans [162], A. niger [59], T. reesei [106, 155, 163] and T. koningii (208), with ace2 and ace1 in T. reesei [69], and with amyR in A. nidulans [136, 165] and N. crassa [159]. …”

Molecular Analysis of AsamyR Gene Encoding Transcriptional Factor for Amylolytic Gene from Shoyu Koji Mold, Aspergillus sojae KBN1340

“…CT-rich stretch was shown to be involved in correct initiation of transcription, and a major transcription start point would exist near the CTstretch (Adams andTimberlake, 1990, Punt et al, 1990). Furthermore, five CreA consensus binding sites were present (-548 to -543, -299 to -294, -258 to -253, -207 to -202, and -77 to -72) and one AmyR binding site was present (-101 to -114 (Tani et al, 2001b, Murakoshi et al, 2012. On the other hand, a typical polyadenylation signal, AATAAA, was not found within the 3'-flanking region we determined.…”