Differential Expression of Ethylene Signaling and Biosynthesis Genes in Floral Organs Between Ethylene-Sensitive and -Insensitive Rose Cultivars

Abstract

The plant hormone ethylene regulates diverse aspects of plant growth and development, including flower senescence and abscission. In cut roses, the impact of ethylene on flower senescence varies greatly depending on the ethylene sensitivity of the floral organs, which is determined by the variety of the rose. To understand the relationship between ethylene synthesis and sensitivity in floral organs, we examined tissue-specific differences in gene expression and regulation using two rose cultivars with differing ethylene sensitivity. We monitored the expression patterns of genes related to ethylene biosynthesis (RhACS1, RhACS2, RhACS3, RhACS4, and RhACO1), receptor (RhETR1, RhETR2, RhETR3, RhETR4, and RhETR5), and signaling (RhCTR1, RhCTR2, RhEIN3-1, RhEIN3-2, and RhEIN3-3) in various floral organs of ethylene-sensitive (SENS; ‘All For Love’) and -insensitive (INSENS; ‘Peach Valley’) rose cultivars. The expression of ethylene-related genes in all floral organs was generally higher in SENS than INSENS cultivars. The presence of exogenous ethylene accelerated the accumulation of RhACS1-4 and RhACO1 transcripts in SENS petals and leaves and in INSENS stamens and stigmas, leading to an increase in RhETR1-5 expression in the floral organs. Meanwhile, RhCTR1-2 expression decreased considerably, with a consequent increase in RhEIN3 transcripts in SENS petals and leaves and INSENS stamens and stigmas. The differential expression of ethylene- related genes in the same tissues indicates that the site of initiation of the ethylene-inducible responses varies among the varieties, and this is probably related to the ethylene sensitivity of the flowers.