Preliminary Molecular Mechanisms Of The Red Seaweed Gloiopeltis Furcata Responding To Dehydration

The tidal changes can cause intertidal seaweeds to dry out and submerge periodically every day.During low tide,intermittent dehydration can cause morphological changes and intracellular oxidative damage,affecting physiological responses and related metabolic processes of seaweeds.However,the adaptive molecular mechanisms of intertidal seaweeds and genes related to dehydration are still not clear.In this study,Gloiopeltis furcata,the intertidal red seaweed with strong tolerance to dehydration,was selected as our model.Two successive dehydration-rehydration cycles were designed within 24 hours in laboratory to simulate the natural semi-diurnal tides.Total antioxidant capacity(T-AOC)and antioxidant enzyme activities(CAT,SOD,TrxR)of G.furcata were measured during two cycles,transcriptome sequencing and weighted gene co-expression network analysis(WGCNA)were used to explore potential molecular pathways and key genes associated with dehydration.The transcriptional expression of candidate dehydration response genes involved in the processes of signal transduction,ubiquitination,floridoside synthesis,antioxidant and detoxification were verified by quantitative reverse transcription PCR technology(qRT-PCR).The relevant results are as follows:The results of antioxidant enzymes activity assay showed that,the antioxidant capacity was crucial for G.furcata in response to dehydration stress.Catalase(CAT),thioredoxin reductase(TrxR)and superoxide dismutase(SOD)participate in antioxidant process,and the activity of CAT is particularly important for the resistance to dehydration.Transcription sequencing assembled 32,681 unigenes in total,of which 12,813 were annotated.The CG content was 55.32%,and N50 length was 1238 bp.Compared with control group,there were 7,161 differentially expressed genes(DEGs)in treatment groups.WGCNA divided all unigenes into 20 modules,and Coral2 was identified as the key module related to dehydration by expressionpatterns analyzing.KEGG pathways enrichment analysis of Coral2 found that ubiquitin mediated proteolysis pathway(UPP)and phosphatidylinositol(PI)signaling system were significantly enriched in Coral2,and may crucial for dehydration response in G.furcata.Networks establishing suggested that genes encoding ubiquitin-protein ligase E3(GfE3-1),SUMO-activating enzyme sub-unit 2(GfSAE2),calmodulin(GfCaM)and inositol-1,3,4-trisphosphate 5/6-kinase(GfITPK)were the hubs in UPP network and PI signal system network,they showed connections with some transcription factors and genes related to RNA modification and osmotic regulation.During two dehydration processes,transcriptional expressions of GfE3-1,GfSAE2,GfCAM and GfITPK were up-regulated.In addition,qRT-RCR results showed that mRNA expression levels of genes encoded heat shock protein 70(GfHSP70),carbonic anhydrase(GfCA)and glutathione S-transferase(GfGST)were also positively correlated with dehydration stress,and key genes of floridoside synthesis(GfUGPase,GfGK,GfGPDH)only responded to first dehydration treatment.In this study,it is believed that PI signaling system interact with calcium signaling system to transduce the dehydration stress signal and activate downstream responses.While ubiquitination may act as an important post-translational modification to participate in dehydration response.Antioxidant enzymes and other downstream functional genes directly resist the oxidative damage caused by water loss.The results of this study provide important reference to understand how intertidal red seaweeds respond to periodic dehydration and rehydration processes and their adaptive molecular mechanisms.