Characterization of an ethylene receptor family with differential expression in rose (Rosa hybrida L.) flowers

To analyze differences in flower longevity and ethylene sensitivity, we isolated Rosa hybrida gene fragments with sequence similarity to the Arabidopsis thaliana ethylene receptor gene-family. A rose gene (RhETR1) highly similar to AtERS1 had been previously sequenced. Here, we report the isolation of three additional partial rose genes (RhETR2-4) belonging to different sub-groups of ethylene receptor genes. RhETR2 clusters with AtETR1, RhETR4 with AtERS1 and RhETR1, whereas RhETR3 shows high sequence similarity to AtETR2 and AtERS2. Expression analysis of RhETR2 and RhETR3 revealed that they are differentially expressed. RhETR2 is expressed at a constitutive level throughout newer development whereas RhETR3 expression increases in senescing flowers of the cultivar 'Bronze' which has a short floral life while it remains at low levels in the long-lasting flowers of the cultivar 'Vanilla'. Expression of both genes was increased by ABA and ethylene treatment, but transcript abundance differed between rose cultivars with different postharvest performance. These results indicate that differences in flower life among rose cultivars could be due to differences in receptor levels.