Results and discussion
Cloning and recombinant expression of amyA and glaA
Amplification of the A. tubingensis amyA cDNA yielded
a 1 860 base pair (bp) fragment with 99.8% DNA sequence
homology to the A. kawachii α-amylase gene [Genbank:
AB008370]. Amplification of the A. tubingensis glaA cDNA
yielded a 1 920 bp fragment with 99.3% DNA homology to
the A. shirousami glucoamylase cDNA [Genbank: D10460
and E02366], as well as 100% homology over 1 917 bp with
the A. tubingensis glucoamylase gene, glaA (GenBank:
AY528665). The cDNA sequence of the A. tubingensis α-
amylase gene (amyA) and predicted amino acid sequence
were deposited [GenBank: JF809672].
The amyA and glaA genes were subcloned individually
and combined in yBBH1-derived plasmids (Figure 1,
Table 1) and transformed into the laboratory strain S. cerevisiae
Y294. The S. cerevisiae strains expressing α-amylase
(AmyA) developed clearing zones on solid SC-URA media
containing 2% soluble starch (Figure 2), whilst zones were
neither expected nor observed for strains expressing
the exo-type glucoamylase. Similar results were obtained
when the corresponding plasmids were transformed in S.
cerevisiae Mnuα1 strain, a haploid strain derived from the
industrial MH1000 strain (Table 1).