| Auricularia auricula(L.)Underw,also known as agaric,is a popular edible and medicinal mushroom.It has remarkable effects in lowering blood sugar and lipid,anti-cancer,oxidation resistance and other aspects.Strontium(Sr)belongs to the alkaline soil metal element,which is one of the 14 trace elements essential to the human body.It has played an irreplaceable role in the prevention and treatment of certain major diseases such as osteoporosis.In this study,the optimal strontium-rich strains were selected by strontium enrichment treatment using different varieties of Auricularia auricula strains as test materials.We extracted polysaccharides,proteins,nucleic acids and inorganic substances from the mycelium and fruiting bodies of the best strontium-rich Auricularia auricula and determined the strontium content,and initially determined the state of strontium deposition in the cells.Combined with the transcriptome sequencing results,the metabolic pathways and genes related to strontium enrichment were analyzed to explore the molecular regulatory mechanism of strontium enrichment in Auricularia auricula.The main findings of this paper are presented as follows:1.Selection of strontium-rich Auricularia auricula strains.Five strains of Auricularia auricula(Xinke,Shennong A8,Qindan 4#,LS-256 and Er 91)were used as test materials and the morphology changes of fungal mycelium were observed under the conditions of strontium treatment concentration of 0 mg/L,400mg/L,800 mg/L,1200 mg/L,1600 mg/L and 2000 mg/L.The results showed that in the original medium,the Auricularia auricula mycelium was white,and dense and evenly distributed;in strontium-containing medium,the mycelium of Xinke,Qindan 4#,LS-256 and Er 91 was curled and the peripheral mycelium was sparse,and the change of mycelium morphology of Shennong A8 under strontium treatment was not obvious.The growth rates of different strains in strontium-containing medium were measured,and the main results were as follows: The growth rate of 5 Auricularia auricula strains under the highest strontium concentration(2000 mg/L)treatment was ranked as Shennong A8(0.62 cm/d)> LS-256(0.6 cm/d)> Qindan 4#(0.58 cm/d)> Xinke(0.56 cm/d)> Er 91(0.38 cm/d).The mycelium biomass and strontium absorption rate of Shennong A8,Qindan 4# and LS-256 strains cultured after 10 days in a liquid shake bottle containing400 mg/L strontium were determined.The biomass is 6.95 cm/d,6.3 cm/d and 3.65cm/d,respectively,and the absorption rate of strontium is 85 %,84 % and 88 %,respectively.2.The state of strontium deposition in the cells.The polysaccharides,proteins,nucleic acids and inorganic substances in two physiological periods of Shennong A8 were extracted by hot water extraction,ultrasound-assisted alkali method and concentrated salt method,respectively.By microwave digestion and inductively coupled plasma atomic emission spectrometry(ICP-AES),the total strontium content and the strontium content in each substance were determined.It was found that strontium was mainly present in polysaccharides,proteins and other organic substances.Under the treatment of 400 mg/L strontium,the total amount of strontium absorbed by Shennong A8 mycelium is 572.70 mg/kg,in which the contents of strontium bound to polysaccharides,protein,nucleic acid,inorganic substances and other organic matter accounted for 50.6 %,0.9 %,3.9 %,0.3 % and44.3 % of the total strontium content,respectively;Under 400 mg/kg strontium treatment,cultivation of Shennong A8 fruiting body that the addition of strontium increasd the yield of Shennong A8 from 33.975 g per bag to 42.601 g per bag and the strontium absorption was measured to be 226.29 mg/kg.The strontium content combined with polysaccharide,protein,nucleic acid,inorganic and other organic compounds accounted for 16.14 %,43.1 %,1.1 %,5.2 % and 34.1 %,respectively of the total strontium content.3.Molecular mechanism of response to strontium element in Shennong A8 under strontium treatment.The mycelium of Shennong A8 was treated at 400 mg/L strontium concentration and the fruiting bodies of Shennong A8 were treated at 400 mg/kg strontium concentration,and the treated and control materials(without strontium addition)were subjected to transcriptome sequencing analysis.After library construction and high-throughput sequencing,a total of 90.69 Gb of high quality sequencing fragments were obtained,and 248,171 transcripts with 49,260 genes were obtained by de novo assembly of sample gene fragment data.Among them,459 differentially significant genes were detected in mycelium,320 genes were up-regulated and 139 genes were down-regulated under strontium-rich conditions,and the number of up-regulated genes was larger than the number of down-regulated genes;57 differentially significant genes were detected in the fruiting bodies group,only 2 genes were up-regulated and 55 genes were down-regulated under strontium-rich conditions,and the number of up-regulated genes was smaller than the number of down-regulated genes.The number of up-regulated genes was smaller than the number of down-regulated genes.Only 4differential genes were co-expressed by the mycelium and fruiting bodies of Shennong A8 after strontium enrichment treatment.The 248 differential genes of strontium-enriched mycelium of Shennong A8 were annotated into the functional entries of 37 GOs in three categories: biological processes,cellular components,and molecular functions.According to these entries,strontium enrichment treatment could significantly affect physiological and biochemical processes such as oxidoreductase,cell membrane,iron ion binding and carbohydrate metabolism in the mycelium of Auricularia auricular;in the fruiting bodies group,32 differential genes were annotated in 24 subcategories by GO database,according to these entries know rich strontium treatment can significantly affect protein folding and unfolding in endoplasmic reticulum,where genes with up-regulated expression were annotated in functions such as membrane composition and transmembrane transporter activity,while the expression of the remaining annotated differential genes showed down-regulation.This indicates that in the fruiting bodies the protein response to strontium is more intense after strontium enrichment treatment.Selection of 10 significantly different genes associated with metal transporters after strontium treatment,namely MUP1,tbp1,FUS6,SPAC3H1.06 c,SPCC965.06,cic A,xan B,SPAC1002.16 c,cns O,gst2,where the genes(FUS6,MFS1)encoding ion efflux pumps were down-regulated,and the expression of genes encoding ABC transporter protein and glutaminase were up-regulated.These genes play a key role in strontium enrichment of Shennong A8,which laid the foundation for further in-depth study of strontium enrichment mechanism of Auricularia auricula. |
PDF Full Text Request