Expression of a phenylalanine ammonia-lyase gene in relation to aril breakdown in harvested longan fruit.

A full-length phenylalanine animonia-lyase gene (PAL) eDNA, named DIPAL1 , was isolated and characterised from harvested longan fruit. The expression pattern of DIPAL1 and PAL activities in relation to aril breakdown in longan fruit stored at different temperatures were investigated. The results showed that both PAL activity and the accumulation of DlPAL1 mRNA increased during storage at 25°C and at 10°C, which coincided with an increase in the aril breakdown index (ABI). The increase in PAL activity or in the accumulation of DIPAL1 mRNA coincided with the increase in ABI in fruit stored at 4°C for 40 d, then transferred to 25°C for 2 d. No accumulation of DIPAL1 mRNA throughout storage at 4°C could be detected, although the increase in PAL activity was in accordance with the increase in ABI. Furthermore, changes in DlPAL1 mRNA accumulation were not fully in accordance with the changes observed in PAL activity, and a rapid increase in PAL activity in arils was observed as an! breakdown occurred rapidly whether fruit were stored at 25°C, 4°C, or 10°C, or moved from 4°C to 25°C. These results suggested that PAL activity is closely involved in aril breakdown in longan fruit, and that PAL activity might be regulated at the posttranscriptional level during aril breakdown. [ABSTRACT FROM AUTHOR]