Isolation and characterisation of a cDNA encoding a novel cytosolic ascorbate peroxidase from potato plants (Solanum tuberosum L.)

Ascorbate peroxidase (APX) is one of the key enzymes of the plant antioxidant system playing, along with catalase, a central role in hydrogen peroxide scavenging. An approach to further increase the knowledge about cytosolic APX gene organization can be achieved by isolating and characterisating new cDNAs, thus providing new insights about the physiological roles and regulation of these enzymes. A partial cDNA clone (corresponding to the 3’ untranslated region), cytosolic ascorbate peroxidase-related, was isolated from potato sprouts by RT-PCR. Database analysis retrieved several expressed sequence tags (ESTs) coding potato cytosolic ascorbate peroxidase, that were used to infer the complete cDNA sequence. The deduced amino acid sequence revealed high homologies with other plant cytosolic ascorbate peroxidases, confirming the reliability of the virtual cDNA. Northern blot analysis revealed the existence of a single band related to the isolated cDNA and the southern blotting results allowed the elaboration of a possible gene organization.