Transcriptome and structure analysis in root of Casuarina equisetifolia under NaCl treatment

Yujiao Wang; Jin Zhang; Zhenfei Qiu; Bingshan Zeng; Yong Zhang; Xiaoping Wang; Jun Chen; Chonglu Zhong; Rufang Deng; Chunjie Fan

doi:10.7717/peerj.12133

Transcriptome and structure analysis in root of Casuarina equisetifolia under NaCl treatment

PeerJ. 2021 Sep 22:9:e12133. doi: 10.7717/peerj.12133. eCollection 2021.

Authors

Affiliations

¹ State Key Laboratory of Tree Genetics and Breeding, Key Laboratory of State Forestry and Grassland Administration on Tropical Forestry, Research Institute of Tropical Forestry, Chinese Academy of Forestry, Guangzhou, China.
² State Key Laboratory of Subtropical Silviculture, School of Forestry and Biotechnology, Zhejiang A&F University, Hangzhou, Zhejiang, China.
³ South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China.

^# Contributed equally.

Abstract

Background: High soil salinity seriously affects plant growth and development. Excessive salt ions mainly cause damage by inducing osmotic stress, ion toxicity, and oxidation stress. Casuarina equisetifolia is a highly salt-tolerant plant, commonly grown as wind belts in coastal areas with sandy soils. However, little is known about its physiology and the molecular mechanism of its response to salt stress.

Results: Eight-week-old C. equisetifolia seedlings grown from rooted cuttings were exposed to salt stress for varying durations (0, 1, 6, 24, and 168 h under 200 mM NaCl) and their ion contents, cellular structure, and transcriptomes were analyzed. Potassium concentration decreased slowly between 1 h and 24 h after initiation of salt treatment, while the content of potassium was significantly lower after 168 h of salt treatment. Root epidermal cells were shed and a more compact layer of cells formed as the treatment duration increased. Salt stress led to deformation of cells and damage to mitochondria in the epidermis and endodermis, whereas stele cells suffered less damage. Transcriptome analysis identified 10,378 differentially expressed genes (DEGs), with more genes showing differential expression after 24 h and 168 h of exposure than after shorter durations of exposure to salinity. Signal transduction and ion transport genes such as HKT and CHX were enriched among DEGs in the early stages (1 h or 6 h) of salt stress, while expression of genes involved in programmed cell death was significantly upregulated at 168 h, corresponding to changes in ion contents and cell structure of roots. Oxidative stress and detoxification genes were also expressed differentially and were enriched among DEGs at different stages.

Conclusions: These results not only elucidate the mechanism and the molecular pathway governing salt tolerance, but also serve as a basis for identifying gene function related to salt stress in C. equisetifolia.

Keywords: Differentially expressed genes; Epidermal cells; Ion content; Programmed cell death; Salt stress.

Grants and funding

This work was supported by a grant from the Specific Program for National Non-profit Scientific Institutions (CAFYBB2018ZB003), a project funded by the National Natural Science Foundation of China (Grant No. 31770716). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.