Cloning of genes encoding cell wall modifying enzymes and their expression in persimmon fruit

Persimmon fruit undergoes intensive cell wall modification during fruit softening after harvest. In this study, we cloned three cDNAs for cellulase (Cel), one cDNA for polygalacturonase (PG) and two cDNAs for expansin, employing RT-PCR cloning techniques used with 'Hiratanenashi' fruit. The changes in each gene expression were determined by northern analysis during shelf-life at 20°C in 'Hiratanenashi' fruit treated with ethanol to remove astringency. In order to determine the ethylene dependence of each gene expression, some fruit were exposed to 1-methylcyclopropene (MCP), a strong inhibitor of ethylene perception, or propylene, analog of ethylene, prior to de-astringency. The accumulation of DK-Cel3, DK-PG1, and DK-Exp2 mRNAs were induced simultaneously with commencement of ethylene production and fruit softening in the fruit. The MCP pre-treatment delayed the accumulation of these mRNAs and also fruit softening while propylene treatment resulted in the accumulation of these mRNAs within one day and a rapid fruit softening. On the other hand, mRNAs for DK-Cel1, DK-Cel2, and DK-Exp1 had already accumulated in the fruit at harvest and decreased during shelf-life. These results indicate that the ethylene dependent gene expression of DK-Cel3, DK-PG1, and DK-Exp2 is closely involved in fruit softening of 'Hiratanenashi' persimmon.