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

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 (AccytMDH) and vacuolar (H+)-ATPase c subunit (AcVHA-c) were isolated from Annona cherimola using the reverse transcriptase polymerase chain reaction (RT- PCR) and rapid amplification of cDNA ends (RACE). The AccytMDH codes for a 332 amino acid polypeptide with a predicted molecular mass of 35.6 kDa. The deduced amino acid sequence for AccytMDH shared high identity with other plant homologous malate dehydrogenase proteins. The AcVHA-c 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 AcVHA-c revealed four transmembrane domains highly conserved among plant counterparts. The expression of AccytMDH and AcVHA-c, 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 AccytMDH and AcVHA-c as molecular targets new strategies can be exploited to get a clear picture in the ripening of cherimoya.