Molecular cloning and characterization of cDNAs encoding cytosolic malate dehydrogenase and vacuolar (H⁺)-ATPase in <em>Annona cherimola</em> and their expression during postharvest ripening

Abstract

This study aims to investigate the expression of two cherimoya genes putatively related to fruit ripening. Two full-length cDNAs encoding cytosolic NAD-dependent malate dehydrogenase (<em>AccytMDH</em>) and vacuolar (H⁺)-ATPase c subunit (<em>AcVHA-c</em>) were isolated from <em>Annona cherimola</em> using the reverse transcriptase polymerase chain reaction (RT- PCR) and rapid amplification of cDNA ends (RACE). The <em>AccytMDH</em> codes for a 332 amino acid polypeptide with a predicted molecular mass of 35.6 kDa. The deduced amino acid sequence for <em>AccytMDH</em> shared high identity with other plant homologous malate dehydrogenase proteins. The <em>AcVHA-c</em> encodes a proteolipid subunit of the V-type proton ATPase with 166 amino acids (16.7 kDa). Comparison of the deduced amino acid sequence from <em>AcVHA-c</em> revealed four transmembrane domains highly conserved among plant counterparts. The expression of <em>AccytMDH</em> and <em>AcVHA-c</em>, assessed by semi-quantitative RT-PCR showed that there is an increase in the accumulation of transcripts during postharvest ripening, although not correlated by a significant upsurge of titratable acidity they might contribute to organic acid accumulation and translocation during postharvest ripening of cherimoya in association with other enzymes and carriers. By using <em>AccytMDH</em> and <em>AcVHA-c</em> as molecular targets new strategies can be exploited to get a clear picture in the ripening of cherimoya.