Cloning of a novel stearoyl-acyl desaturase gene from white ash (Fraxinus americana) and evolution analysis with those from other plants

Using reverse transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends, a new full-length cDNAs of stearoyl-ACP desturases (SAD) (FaSAD) was obtained from white ash. Sequence analysis showed that the deduced amino acid sequence of FaSAD has high similarity to that of other reported SAD proteins. They are different from each other by some substitutions, insertions and/or deletions involving single amino acid residues or motifs. The analysis of semi-quantitative RTPCR showed that the expression of SAD gene had the highest level in stem and lowest level in leaves. The tertiary structure prediction indicated that FaSAD protein should be a compact globular protein. Based on evolution analysis, it was clear that the genes from the same family were approximately clustered into a group, but all genes from woody plants were not clustered into a separate group. In woody plants, it was indicated that all sequences clustered into two major groups and the FaSAD from white ash was closely related to the SAD gene from Macfadyena unguis-cati.