Expression Patterns of the Heat Shock Protein 90 (Hsp90) Gene Suggest Its Possible Involvement in Maintaining the Dormancy of Dinoflagellate Resting Cysts.

Yunyan Deng,Zhangxi Hu,Caixia Yue,Ying Zhong Tang,Fengting Li

doi:10.3390/ijms222011054

Abstract

Heat shock protein 90 (Hsp90) is a highly conserved molecular chaperone functioning in cellular structural folding and conformational integrity maintenance and thus plays vital roles in a variety of biological processes. However, many aspects of these functions and processes remain to be fully elucidated, particularly for non-model organisms. Dinoflagellates are a group of eukaryotes that are exceedingly important in primary production and are responsible for the most harmful algal blooms (HABs) in aquatic ecosystems. The success of dinoflagellates in dominating the plankton community is undoubtedly pertinent to their remarkable adaptive strategies, characteristic of resting cyst production and broad tolerance to stresses of temperature and others. Therefore, this study was conducted to examine the putative roles of Hsp90 in the acclimation to temperature stress and life stage alterations of dinoflagellates. Firstly, we isolated the full-length cDNA of an Hsp90 gene (StHsp90) via RACE from the cosmopolitan HAB species Scrippsiella trochoidea and tracked its transcriptions in response to varied scenarios via real-time qPCR. The results indicated that StHsp90 displayed significant mRNA augment patterns, escalating during 180-min treatments, when the cells were exposed to elevated and lowered temperatures. Secondly, we observed prominently elevated StHsp90 transcriptions in the cysts that were stored at the cold and dark conditions compared to those in newly formed resting cysts and vegetative cells. Finally, and perhaps most importantly, we identified 29 entries of Hsp90-encoding genes with complete coding regions from a dinoflagellate-specific environmental cDNA library generated from marine sediment assemblages. The observed active transcription of these genes in sediment-buried resting cysts was fully supported by the qPCR results for the cold-stored resting cysts of S. trochoidea. Hsp90s expressions in both laboratory-raised and field-collected cysts collectively highlighted the possible involvement and engagement of Hsp90 chaperones in the resting stage persistence of dinoflagellates.

Highlights

Molecular chaperones fulfill foundational and vital functions in cellular proteostasis, including facilitating the proper folding of native proteins and/or stabilizing and refolding of misfolded ones, preventing aberrant aggregation [1,2,3]
The full-length cDNA sequence of StHsp90 was obtained by overlapping the two fragments with the 821-bp fragment amplified by primers P1 and P2
The newly generated sequence spanned 2474 bp, comprising a 106-bp 5’ UTR with the conserved dinoflagellate spliced leader (DinoSL) sequence, a 238-bp 3’ UTR ending in a poly (A) tail, and an ORF of 2130 bp (Supplementary Figure S1)

Summary

Introduction

Molecular chaperones fulfill foundational and vital functions in cellular proteostasis, including facilitating the proper folding of native proteins and/or stabilizing and refolding of misfolded ones, preventing aberrant aggregation [1,2,3]. The known clients of Hsp members to date are enriched in regulatory proteins, such as steroid hormone receptors, transcription factors, kinases, and signal transduction proteins [4,9,10]. These clients reside in nearly every developmental and signaling pathway in eukaryotes, providing a plausible explanation for the broad influences of Hsp90s on the relationship between the genotype and phenotype and pertaining to diverse and even seemingly unrelated physiological processes (e.g., homeostasis maintenance, signal transduction, cell cycle control, and protein trafficking) [2,3,4,6,10,11]

Methods

Results

Discussion

Conclusion