Molecular mechanism underlying Pyropia haitanensis PhHsp22-mediated increase in the high-temperature tolerance of Chlamydomonas reinhardtii

Jing Chang,Yan Xu,Chaotian Xie,Jianzhang Lin,Jianzhi Shi,Wenlei Wang,Changsheng Chen,Dehua Ji

doi:10.1007/s10811-020-02351-6

Jing Chang, Yan Xu + Show 6 more

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https://doi.org/10.1007/s10811-020-02351-6

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Abstract

Global warming is one of the key limiting factors affecting the cultivation of Pyropia haitanensis which is an economically important macroalgae species grown in southern China. However, the mechanism underlying the high-temperature tolerance of P. haitanensis remains largely unknown. In a previous study, we showed that the expression of the small heat shock protein 22 gene (Hsp22) is upregulated in P. haitanensis in response to high-temperature stress, but the associated regulatory mechanism was not fully elucidated. In this study, a transgenic Chlamydomonas reinhardtii expression system was used to functionally characterize P. haitanensis Hsp22. Our analyses indicated that the C-terminal of PhHsp22 is highly conserved and contains an A-crystal structure domain. A phylogenetic analysis revealed PhHsp22 is not closely related to small heat shock protein genes in other species. Additionally, PhHsp22 expression significantly increased at 3 and 6 h after initiating 33 °C treatment, which improved the survival rate of transgenic C. reinhardtii during the early stage of high-temperature treatment. The further transcriptome analysis revealed that PhHsp22 expression can promote pathways related to energy metabolism, metabolites metabolism, and protein homeostasis in transgenic C. reinhardtii cells exposed to high temperatures. Therefore, PhHsp22 may be crucial for the response of Pyropia species to high-temperature stress. Furthermore, this gene may be useful for breeding new high-temperature algal strains.

Highlights

Pyropia species are economically important marine red algae used to produce food, fertilizer, and medicine (Blouin et al 2011; Brawley et al 2017; Cao et al 2020)
A phylogenetic analysis supported the existence of a sister-group relationship between P. haitanensis and Chondrus crispus but implied that Pyropia species diverged from Cyanophyta, Chlorophyta, Phaeophyta, and land plant species (Fig. 1b)
In the present study we determined that PhHsp22 contained the theoretical domain of ACD and HSP20, which is consistent with the domains of Arabidopsis thaliana Small heat shock proteins (sHSPs) (Scharf et al 2001)

Summary

Introduction

Pyropia species are economically important marine red algae used to produce food, fertilizer, and medicine (Blouin et al 2011; Brawley et al 2017; Cao et al 2020). With the expansion of artificial seeding and the development of a floating culture method, the farming and processing of Pyropia species. Because of global warming, seawater temperatures have gradually increased in recent years which has adversely affected the cultivation and yield of Pyropia species (Shi et al 2017; Wang et al 2018a; Hwang et al 2019). To adapt to global climate change and to continue to develop improved methods for cultivating Pyropia species, several high-temperature (HT) tolerant Pyropia haitanensis strains (Z-26, Z-61, and ZS-1) have been selected and are widely cultivated in southern China (Chen et al 2008). Deciphering the molecular basis for the heat stress tolerance of P. haitanensis is important for increasing the commercial value and productivity of red algal species

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