Figure 4
Validation of poplar FLcDNAs by comparison to reciprocal BLAST matches against Arabidopsis peptides and previously published poplar FLcDNAs. The set of 4,664 poplar FLcDNAs were compared using BLASTX to both The Arabidopsis Information Resource (TAIR) non-redundant Arabidopsis peptide set (28,952 sequences [56]) and a collection of 1,409 previously published poplar sequences from the non-redundant (NR) division of GenBank ([57], the NR release of December 19th, 2006) annotated as full-length (excluding predicted proteins derived from genomic DNA). FLcDNAs were excluded from the analysis when the in-house BLAST-aided ORF detection software identified a FLcDNA as problematic according to the following categories: truncation at the 5'-end (319), truncation at the 3'-end (50), frameshift (12), stop codon in the middle of an ORF (9), or inverted insert (3) [see Additional file 1]. No problematic features were identified in the remaining 4,271 FLcDNAs. This comparison identified 2,774 homologous Arabidopsis-poplar pairs and 288 homologous poplar transcript pairs. A FLcDNA pair was considered homologous if (1) the top BLASTX match exceeded a stringent threshold (% identity ≥ 50%; expect value ≤ 1e-20) and (2) the reciprocal TBLASTN analysis identified the same poplar FLcDNA with a score value equal to or within 10% of the top match. ORF lengths for Arabidopsis and public poplar sequences were extracted from the TAIR and NR records, respectively, and poplar ORF lengths from this study were predicted using either the EMBOSS getorf or in-house BLAST-aided programs (see Figure 2 legend). The greyscale shading of each hexagon represents poplar FLcDNA abundance. ORF lengths for three Arabidopsis-poplar pairs and eight homologous poplar transcript pairs differed by more than 500 aa and are not included in the figure.