Transcriptome sequencing reveals the senescence mechanism of ethylene-insensitive cut Rhododendron flowers

Abstract

Cut rhododendron flowers have high ornamental value and are loved by consumers. It is important to clarify the senescence mechanism of cut rhododendron flowers to prolong their vase life. Transcriptome sequencing was used to investigate flower senescence in four stages of Rhododendron ‘Hong Shanhu.’ Using RNA sequencing, we generated approximately 100.17 Gb clean data and 173,502 annotated unigenes. Ethylene biosynthesis genes, ACOs , had different expression trends, and most ethylene signaling genes had low expression levels. The ethylene release rate and the activities of ACS and ACO were on the rise during cut flower development. The effects of 200 mg/L ethephon and 0.1 mM/L spermidine on vase life and fresh weight were limited. Most of the LEA and Dehydrin were upregulated with cut flower development and the fresh weight was decreased during fully flowering stage. Based on the different expression trends, differentially expressed genes were classified into 10 clusters. Cluster 2 showed significant upregulation between Z4 and Z3, suggesting that the genes in this cluster were upregulated, probably due to the senescence of cut flowers. The overall trend of Cluster 7 was positively correlated with the opening process of cut flowers. Cluster 9 had a peak at Z3, which indicated that the unigenes started the senescence process. bZIP53, RAP2.4, UIF1, HAT5, ILR3, DEAR3, SCL8, TZF10, MYB70, ERF5, ERF9, and CBF1 had higher expression levels than the other transcription factors in these clusters, indicating that they are probably the key transcription factors involved in petal senescence. Our results indicated that ‘Hong Shanhu’ cut flowers were ethylene-insensitive, and their senescence was probably related to water stress. These results contribute to understanding the mechanism of senescence in cut rhododendron flowers.