Genome-wide isolation and expression analysis of vacuolar processing enzyme (<i>VPE</i>) gene family in four apple cultivars with different storability

This research was undertaken to determine expression patterns of vacuolar processing enzyme (<i>VPE</i>) genes in four apple (<i>Malus domestica</i> (Suckow) Borkh) cultivars ‘Royal Gala (RG)’, ‘Golden Delicious (GD)’, ‘Ralls Janet (RJ)’ and ‘Fuji (FJ)’ during ripening. The results showed that GD and RG had higher respiration rate, ethylene production, content of malondialdehyde (MDA), relative electrical conductivity (REC) and VPE activity than RJ and FJ during ripening. A total of 17 <i>MdVPEs</i> were found to be expressed in four cultivars. These <i>MdVPEs</i> exhibited different expression patterns during ripening of four cultivars. Generally, <i>MdVPEβ1</i>, <i>MdVPEγ2</i>, <i>MdVPEγ4</i> and <i>MdVPEδ7</i> might be closely associated with ripening of all cultivars. <i>MdVPEα6</i> might have a role in the early period of ripening of <i>ACS1–2/-2</i> (1-Aminocyclopropane-1-carboxylate synthase) homozygous cultivars (RG, RJ and FJ). Our data here would be helpful in understanding the associations between <i>MdVPEs</i> and storage properties of different apple cultivars.