Abstract
Flowers of fragrant roses such as Rosa bourboniana are ethylene-sensitive and undergo rapid petal abscission while hybrid roses show reduced ethylene sensitivity and delayed abscission. To understand the molecular mechanism underlying these differences, a comparative transcriptome of petal abscission zones (AZ) of 0 h and 8 h ethylene-treated flowers from R. bourboniana was performed. Differential regulation of 3700 genes (1518 up, 2182 down) representing 8.5% of the AZ transcriptome was observed between 0 and 8 h ethylene-treated R. bourboniana petal AZ. Abscission was associated with large scale up-regulation of the ethylene pathway but prominent suppression of the JA, auxin and light-regulated pathways. Regulatory genes encoding kinases/phosphatases/F-box proteins and transcription factors formed the major group undergoing differential regulation besides genes for transporters, wall modification, defense and phenylpropanoid pathways. Further comparisons with ethylene-treated petals of R. bourboniana and 8 h ethylene-treated AZ (R. hybrida) identified a core set of 255 genes uniquely regulated by ethylene in R. bourboniana AZ. Almost 23% of these encoded regulatory proteins largely conserved with Arabidopsis AZ components. Most of these were up-regulated while an entire set of photosystem genes was prominently down-regulated. The studies provide important information on regulation of petal abscission in roses.
Highlights
Flowers of fragrant roses such as Rosa bourboniana are ethylene-sensitive and undergo rapid petal abscission while hybrid roses show reduced ethylene sensitivity and delayed abscission
Abscission is known in several plants, the key determinants of abscission have primarily been identified in the model plant Arabidopsis where genes like HAESA and HAESA LIKE2 encoding LRR type receptor kinases[35,36,37], IDA35,37, AGL1538, AGL1839, MAP kinases MPK3 and MPK637, NEVERSHED40, EVERSHED41, FOREVER YOUNG FLOWER42, have been characterized
A total of 32,961 genes were found expressing in the rose petal abscission zones (AZ) transcriptome out of 43,301 genes predicted in the genome
Summary
Flowers of fragrant roses such as Rosa bourboniana are ethylene-sensitive and undergo rapid petal abscission while hybrid roses show reduced ethylene sensitivity and delayed abscission. Differential regulation of 3700 genes (1518 up, 2182 down) representing 8.5% of the AZ transcriptome was observed between 0 and 8 h ethylene-treated R. bourboniana petal AZ. Almost 23% of these encoded regulatory proteins largely conserved with Arabidopsis AZ components. Most of these were up-regulated while an entire set of photosystem genes was prominently down-regulated. Organ abscission is an important developmental process that regulates the detachment of leaves, flowers, flower parts, fruits etc. Mutants of ethylene perception and signaling show delayed organ abscission in Arabidopsis and tomato[13,14,15,16,17,18,19]. Auxin inhibits or delays abscission in leaves, flower and fruits[1, 2]. Regulatory genes controlling abscission remain to be identified
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