[Isolation and expression profiling of the Pto-like gene SsPto from Solanum surattense]

A novel Pto-like gene (designated as SsPto) is cloned from yellow-fruit nightshade (Solanum surattense). The full-length cDNA of SsPto is 1331 bp long with an open reading frame of 960 bp encoding a polypeptide of 320 amino acid residues. The deduced SsPto protein has a calculated molecular weight of 36.21 kDa with an isoelectric point of 6.18. Multiple sequence alignment shows that SsPto protein shares 71.4% and 71.6% identities to Pto proteins from Lycopersicon pimpinellifolium and L. hirsutum respectively. Genomic Southern blot analysis indicates the presence of a small family of SsPto in the S. surattense genome. SsPto is found to be constitutively expressed in the S. surattense plant with the highest expression in stems. However, under induction by TMV for 6 days, SsPto expresses the highest in roots. Further expression analysis reveals that the signaling components of defense/stress pathways, such as methyl jasmonate (MeJA), salicylic acid (SA), gibberellic acid (GA3) and hydrogen peroxide (H2O2), up-regulate the SsPto transcript levels over the control. Cold treatment, nevertheless, has no significant effect on SsPto expression whereas SsPto expression is down-regulated by dark treatment. Our findings suggest that this novel stress- and pathogen-inducible SsPto from S. surattense may participate not only in the defense/stress responsive pathways, but also in diverse processes of plant's growth and development.