Abstract
BackgroundIntermittent dehydration caused by tidal changes is one of the most important abiotic factors that intertidal seaweeds must cope with in order to retain normal growth and reproduction. However, the underlying molecular mechanisms for the adaptation of red seaweeds to repeated dehydration-rehydration cycles remain poorly understood.ResultsWe chose the red seaweed Gloiopeltis furcata as a model and simulated natural tidal changes with two consecutive dehydration-rehydration cycles occurring over 24 h in order to gain insight into key molecular pathways and regulation of genes which are associated with dehydration tolerance. Transcription sequencing assembled 32,681 uni-genes (GC content = 55.32%), of which 12,813 were annotated. Weighted gene co-expression network analysis (WGCNA) divided all transcripts into 20 modules, with Coral2 identified as the key module anchoring dehydration-induced genes. Pathways enriched analysis indicated that the ubiquitin-mediated proteolysis pathway (UPP) and phosphatidylinositol (PI) signaling system were crucial for a successful response in G. furcata. Network-establishing and quantitative reverse transcription PCR (qRT-PCR) suggested that genes encoding ubiquitin-protein ligase E3 (E3–1), SUMO-activating enzyme sub-unit 2 (SAE2), calmodulin (CaM) and inositol-1,3,4-trisphosphate 5/6-kinase (ITPK) were the hub genes which responded positively to two successive dehydration treatments. Network-based interactions with hub genes indicated that transcription factor (e.g. TFIID), RNA modification (e.g. DEAH) and osmotic adjustment (e.g. MIP, ABC1, Bam1) were related to these two pathways.ConclusionsRNA sequencing-based evidence from G. furcata enriched the informational database for intertidal red seaweeds which face periodic dehydration stress during the low tide period. This provided insights into an increased understanding of how ubiquitin-mediated proteolysis and the phosphatidylinositol signaling system help seaweeds responding to dehydration-rehydration cycles.
Highlights
Intermittent dehydration caused by tidal changes is one of the most important abiotic factors that intertidal seaweeds must cope with in order to retain normal growth and reproduction
Twenty-four cDNA libraries were generated by RNA sequencing, and the number of reads per library ranged from 21.90 M to 34.58 M (Additional file 1: Table S1)
We found seven genes involved in genetic information processing, two genes encoded for sub-units 2 and 6 of the transcription factor TFIID (Gf03506/TFIID2, Gf26104/TFIID6); one gene encoded the alpha sub-unit of transcription initiation factor IIE (Gf17133/TFIIE by KO ID) and one gene encoded for the zinc-finger domain containing protein (Gf31441/ZFP) (Fig. 3b and Table 3); three othergenes were involved in RNA processing, such as Gf06149
Summary
Intermittent dehydration caused by tidal changes is one of the most important abiotic factors that intertidal seaweeds must cope with in order to retain normal growth and reproduction. Seaweeds growing in the intertidal zone are subject to sometimes extreme abiotic stresses during low tide, such as dehydration, strong solar irradiance and fluctuating temperature [1, 2]. Among all of these stressors, dehydration of the algal tissues is one of the most important limitations determining the upper and lower vertical distributions of intertidal seaweeds [3, 4]. It is of great significance to study both the adaptive and tolerance mechanisms of seaweeds when responding to water deficit stress caused by exposure
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