Molecular adaptation to salinity fluctuation in tropical intertidal environments of a mangrove tree Sonneratia alba

Abstract

Background: Mangroves have adapted to intertidal zones-the interface between terrestrial and marine ecosystems. Various studies have shown adaptive evolution in mangroves at physiological, ecological, and genomic levels. However, these studies paid little attention to gene regulation of salt adaptation by transcriptome profiles. Results: We sequenced the transcriptomes of Sonneratia alba under low (fresh water), medium (half the seawater salinity), and high salt (seawater salinity) conditions and investigated the underlying transcriptional regulation of salt adaptation. In leaf tissue, 64% potential salinity-related genes were not differentially expressed when salinity increased from freshwater to medium levels, but became up-or down-regulated when salt concentrations further increased to levels found in sea water, indicating that these genes are well adapted to the medium saline condition. We inferred that both maintenance and regulation of cellular environmental homeostasis are important adaptive processes in S. alba. i) The sulfur metabolism as well as flavone and flavonol biosynthesis KEGG pathways were significantly enriched among up-regulated genes in leaves. They are both involved in scavenging ROS or synthesis and accumulation of osmosis-related metabolites in plants. ii) There was a significantly increased percentage of transcription factor-encoding genes among up-regulated transcripts. High expressions of salt tolerance-related TF families were found under high salt conditions. iii) Some genes up-regulated in response to salt treatment showed signs of adaptive evolution at the amino acid level and might contribute to adaptation to fluctuating intertidal environments. Conclusions: This study first elucidates the mechanism of high-salt adaptation in mangroves at the whole-transcriptome level by salt gradient experimental treatments. It reveals that several candidate genes (including salt-related genes, TFencoding genes, and PSGs) and major pathways are involved in adaptation to high-salt environments. Our study also provides a valuable resource for future investigation of adaptive evolution in extreme environments.

Depth-related Variability of Biological Nitrogen Fixation and Diazotrophic Communities in Mangrove Sediments

“…Located at the transition between ocean and land, mangrove sediments experienced the tidal uctuation day after day [63]. Probably due to the continuous scouring of sur cial sediments by tides and the deposition of salinity in depth [64,65], a continuous increase of salinity with depth of mangrove sediments was observed in our study. More interestingly, in agreement with the paddy soil [66] and salt marsh [67], salinity was identi ed as the most important environmental lter for shaping the diazotrophic community structure in mangrove sediments, as revealed by our RDA and SEM results.…”

Regeneration capacity and threats to mangrove areas on the southern coast of Oriental Mindoro, Philippines: Implications to mangrove ecosystem rehabilitation

“…Other factors such as exposure to flooding due to tidal inundation and high salinity are among the potential factors in the low progression rate or possible death of the juveniles. Many studies reported that even the juveniles of salt-tolerant species A. marina and S. alba cannot withstand high salinity and are having low growth performances in this condition (Ball et al 1995;Kodikara et al 2018;Cheng et al 2020;Feng et al 2020).…”

A high-quality genome of the mangroveAegiceras corniculatumaids investigation of molecular adaptation to intertidal environments

“…In general, salt adaptation is both a long-term and dynamic process and involves many morphological, physiological, cellular, and molecular processes (Feng et al, 2020;Ma et al, 2013;Munns and Tester, 2008;Seki et al, 2002). Mangrove trees can induce specific salt-responsive genes and transcription factors to facilitate adaptation to intertidal environments (Feng et al, 2020). The salt overly sensitive (SOS) pathway is a well-defined signaling pathway for controlling ion homeostasis at the cellular and tissue level (Ji et al, 2013).…”

“…Vivipary and high salt tolerance are particularly common in mangroves and rare in other woody plants. Salt tolerance is a long-term and dynamic process influenced by multiple genes involving many morphological, physiological, molecular, and cellular processes (Feng et al, 2020;Ma et al, 2013;Munns and Tester, 2008;Seki et al, 2002). Several important signaling pathways have been identified, especially the salt overly sensitive (SOS) signaling pathway, as well as Ca 2+ -dependent and ABA signaling pathways (Ji et al, 2013).…”