Distinct expression profiles of ripening related genes in the ‘Nanguo’ pear (Pyrus ussuriensis) fruits

Abstract ‘Nanguo’ pear ( Pyrus ussuriensis ) is one of the most important pear varieties in the northern part of China. It is typical climacteric fruit, and the ripening process is controlled by ethylene. In this study, we compared the fruit firmness and ethylene production between non-treated fruits and fruits treated with 1 μl l −1 of 1-MCP (1-Methylcyclopropene, an ethylene inhibitor) under 4 °C or room temperature. The expression of genes involved in ethylene biosynthesis and signal transduction was investigated. Fruits harvested from different locations were also used to compare the gene expression. The results showed that 1-MCP treatment slowed down the fruit firmness drop but did not change the ethylene production very much during storage. The expression of genes involved in ethylene biosynthesis ( ACS1, ACS4 and ACO ), reception ( ERS1a ) and response ( PG1 and PG2 ) were inhibited by 1-MCP treatments, and affected by the treatment temperature. The expression of receptor gene ETR1a showed a constitutive pattern in fruits treated with or without 1-MCP at room temperature, but was induced in treatment under 4 °C. In the fruit harvested from colder area (Shenyang), the ethylene production was higher and fruit firmness was lower than that in fruit harvested from warmer area (Anshan). Moreover, the expression of ethylene biosynthesis and receptor genes was lower in fruit from Shenyang than that from Anshan. PG2 was expressed earlier in fruits from Shenyang than those from Anshan and may play more important role in fruit softening. The possible mechanism under the expression patterns was discussed.