Abstract

Sweet osmanthus (Osmanthus fragrans) is an evergreen woody plant that emits a floral aroma and is widely used in the landscape and fragrance industries. However, its application and cultivation regions are limited by cold stress. Heat-shock transcription factor (HSF) family members are widely present in plants and participate in, and regulate, the defense processes of plants under various abiotic stress conditions, but now, the role of this family in the responses of O. fragrans to cold stress is still not clear. Here, 46 OfHSF members were identified in the O. fragrans genome and divided into three subfamilies on the basis of a phylogenetic analysis. The promoter regions of most OfHSFs contained many cis-acting elements involved in multiple hormonal and abiotic stresses. RNA-seq data revealed that most of OfHSF genes were differentially expressed in various tissues, and some OfHSF members were induced by cold stress. The qRT-PCR analysis identified four OfHSFs that were induced by both cold and heat stresses, in which OfHSF11 and OfHSF43 had contrary expression trends under cold stress conditions and their expression patterns both showed recovery tendencies after the cold stress. OfHSF11 and OfHSF43 localized to the nuclei and their expression patterns were also induced under multiple abiotic stresses and hormonal treatments, indicating that they play critical roles in responses to multiple stresses. Furthermore, after a cold treatment, transient expression revealed that the malondialdehyde (MDA) content of OfHSF11-transformed tobacco significantly increased, and the expression levels of cold-response regulatory gene NbDREB3, cold response gene NbLEA5 and ROS detoxification gene NbCAT were significantly inhibited, implying that OfHSF11 is a negative regulator of cold responses in O. fragrans. Our study contributes to the further functional characterization of OfHSFs and will be useful in developing improved cold-tolerant cultivars of O. fragrans.

Highlights

  • Plant development and growth suffer from the effects of many environmental factors, like cold, heat, salinity and drought

  • The 46 Heat-shock transcription factor (HSF) genes identified in O. fragrans were disproportionately localized on 17 chromosomes

  • The OfHSFs clustered into three classes on the basis of their phylogenetic relationships, and this was supported by the conserved motif distribution

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Summary

Introduction

Plant development and growth suffer from the effects of many environmental factors, like cold, heat, salinity and drought. Many complex molecular regulatory mechanisms for resisting external stresses have evolved in plants. It is well known that a great number of transcription factors (TFs) genes involved in responding to abiotic stresses [1]. Members of the heat-shock transcription factor (HSF) family, as important regulatory elements in plants under stress conditions, function in stress-signaling pathways, signal transduction associated with protein kinase and other stress-related regulatory mechanisms [2]. The HSF family is involved in the regulation of reactive oxygen species (ROS)-signaling pathway that is activated when plants are experiencing stress [3]. The HSF family is involved in the regulation of reactive oxygen species (ROS)-signaling pathway that is activated when plants are experiencing stress [3]. 4.0/).

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