Salinity-Induced Palmella Formation Mechanism in Halotolerant Algae Dunaliella salina Revealed by Quantitative Proteomics and Phosphoproteomics

Abstract

Palmella stage is critical for some unicellular algae to survive in extreme environments. The halotolerant algae Dunaliella salina is a good single-cell model for studying plant adaptation to high salinity. To investigate the molecular adaptation mechanism in salinity shock-induced palmella formation, we performed a comprehensive physiological, proteomics and phosphoproteomics study upon palmella formation of D. salina using dimethyl labeling and Ti4+-immobilized metal ion affinity chromatography (IMAC) proteomic approaches. We found that 151 salinity-responsive proteins and 35 salinity-responsive phosphoproteins were involved in multiple signaling and metabolic pathways upon palmella formation. Taken together with photosynthetic parameters and enzyme activity analyses, the patterns of protein accumulation and phosphorylation level exhibited the mechanisms upon palmella formation, including dynamics of cytoskeleton and cell membrane curvature, accumulation and transport of exopolysaccharides, photosynthesis and energy supplying (i.e., photosystem II stability and activity, cyclic electron transport, and C4 pathway), nuclear/chloroplastic gene expression regulation and protein processing, reactive oxygen species homeostasis, and salt signaling transduction. The salinity-responsive protein–protein interaction (PPI) networks implied that signaling and protein synthesis and fate are crucial for modulation of these processes. Importantly, the 3D structure of phosphoprotein clearly indicated that the phosphorylation sites of eight proteins were localized in the region of function domain.

A Data-Independent-Acquisition-based proteomic approach towards understanding the acclimation strategy ofMicrochloropsis gaditanaCCMP526 in hypersaline conditions

“…The initial response to changes in salinity levels was significantly enriched by the photosynthesis GO-term in cells in both 55 and 100 PSU. Similarly, proteomic analysis on a halotolerant alga Dunaliella salina revealed the dynamics of expression of essential proteins involved in photosynthesis at high salinity conditions (Wei et al, 2017).…”

“…These proteins are involved in maintaining the redox status in higher plants (Chen et al, 2009; Kav et al, 2004; Sugimoto & Takeda, 2009). Likewise, the SOD level was increased in the halotolerant alga Dunaliella salina (Wei et al, 2017) and in a salinity tolerant strain of Chlamydomonas reinhardtii (Sithtisarn et al, 2017). Anti-oxidant proteins help to maintain the ROS level inside the cell, and accumulation of such proteins have been found in salinity treated plants (Miller et al, 2010).…”

“…The proteome of the halotolerant alga Dunaliella sp. has been studied to understand the molecular basis behind tolerance to high saline conditions (Katz et al, 2007; Wei et al, 2017). Sithtisarn et al (2017) performed comparative proteome analysis of a control, and a salinity tolerant strain of Chlamydomonas reinhardtii to understand the salinity tolerance mechanism involved.…”

Phylogenetic analysis of Dunaliella (Chlorophyta) emphasizing new benthic and supralittoral isolates from Great Salt Lake

“…Palmella formation in Dunaliella salina following hypersaline‐shock involves a complex molecular response with many proteins up‐ and down‐regulated (Wei et al. ). It would be interesting to compare gene expression patterns in persistently sarcinoid/palmelloid strains to short‐term induction of this morphology.…”

“…While that could explain this morphology, it is restricted to our isolates from benthic or supralittoral samples (at least for those from Gunnison Bay where we have collection records), implying physiological differences. Palmella formation in Dunaliella salina following hypersaline-shock involves a complex molecular response with many proteins up-and down-regulated (Wei et al 2017). It would be interesting to compare gene expression patterns in persistently sarcinoid/palmelloid strains to short-term induction of this morphology.…”