3. Results
3.1. Nucleotide sequences
50 and 30 RACE produced nine cDNA clones that encoded
apparent laccase sequences (Table S3). These nine sequences have
been deposited in Genbank with accession numbers GQ421909
through GQ421917. Seven of the nine clones encoded highly similar,
full-length ORFs with only 22 variable nucleotide positions
(Fig. S1). All putative start codons were present at the first ATG
following the 50 RACE PCR primer sequence (Fig. S2, primer
sequence not shown). Additionally, the 50 end of the full-length
ORFs are translatable into identical signal peptides, which further
verifies that the complete 50 end of cDNA was captured by RACE
PCR. Based on sequence alignments, three highly similar ORFs
aligned well into one contig (Lac6, Lac7, and Lac19) and the
remaining four into another (Lac12, Lac14, Lac15, and Lac17). These
two contigs are referred to as contig 1 and contig 2, respectively, and
they are considered to represent two potential laccase isoforms.
Comparison of apparent 50 untranslated sequences of the seven
full-length clones agrees 100% with the ORF contig assemblies
(Fig. S2). Overall, the two contigs are 99.4% identical (Fig. S3).
Besides the seven full-length clones noted above, two truncated
clones (Lac13 and Lac20) were also obtained. Lac13 has a deletion of
362 nucleotides at its 50 end and its ORF begins 379 nucleotides
downstream of the consensus ATG start codon (not shown).
Another clone, Lac20, has a 2-nucleotide deletion at consensus
positions 339e340 that results in a frame shift (not shown).