Transcriptome And Metabolome Joint Analysis Of Molecular Regulation Mechanism Of Different Coconut Varieties In Response To Salt Stress

Coconut is the provincial tree of Hainan and plays a very important role in the economy and life of the Hainan people.Unlike other crops,the transmission method of coconuts is very unique.The mature coconut fruit spreads along the ocean currents and germinates on the beach after landing.According to literature records,coconuts in China may have originated from the Malay Peninsula.In the Han Dynasty,It entered China with the ocean currents and formed a local high-species coconut community in Hainan.Due to the spread and growth characteristics of coconuts,coconuts are very salt-tolerant(moderately salty),and moderate irrigation of seawater can increase the production of coconuts.In Hainan,we often see some coconut trees with salt bags hanging to increase coconuts.Tree cold tolerance and yield.However,due to the limitation of the coconut planting area,there are currently very few scientific research units that take coconut as the research object,making the research of coconut lagging behind,and the mechanism of coconut salt tolerance has not been elaborated.In this study,Hainan native high-species,perfume coconut,yellow dwarf and red dwarf were used as research materials.Local tall species,fragrant coconut were more resistant to salt damage,while yellow dwarf and red dwarf were relatively weak.Using transcriptome analysis and metabolome to study the potential molecular mechanism of coconut salt tolerance.In this study,300 mmol / L solution was used to treat four different varieties of coconut seedlings,and the new leaves were divided into two.One of them extracted total RNA from coconut leaves and performed transcriptome sequencing.The other copy was sequenced for metabolic components.Through transcriptome data,we annotate 29109 genes in total and use log to base 2 function to normalize it.Among the four coconut varieties,10 days,5 days and 1 day transcriptome data compared with the 0 day transcriptome data,there were 746 genes with differential expression multiples of more than twice.Combining the differential expression data,we focus on cell wall,cell membrane,soluble small molecules,deoxygen free radicals,and ion channel related genes.Among these genes,there are 15 cell wall related genes,40 lipid related genes,16 transporter related genes,17 active oxygen scavenging substance related genes,3 organic soluble substance related genes,and transcription factor genes.There are 52.Through the analysis of metabolome data,we found that the metabolome data of the four coconut varieties at 10 days,5 days,and 1 days compared with the 0 day metabolome data,there were 440 metabolites with a differential expression multiple of more than 2 times,including flavonoid There are as many as 147 substances.After a joint analysis of the transcriptome and metabolome data of four different varieties of coconut,the following conclusions are drawn.Coconut may respond to salt stress mainly through four aspects: thickening of the stratum corneum,changes in cell wall structure,increase in biofilm transport proteins,and increase in reactive oxygen species.1.Wax synthesis genes CER1,CER2,CER3 and non-specific lipotransfer protein genes LTP3,LTP4,LTP5 related to thickening of the stratum corneum.Compared with other lipid-related expressed genes,it has higher expression level and differential expression factor.Among them,the differential expression multiple of CER2 is the highest,up to 6 times and the FPKM value is above 100 in all four varieties.2.Cell wall related genes cellulose synthase gene CSLD1 and xyloglucan transglycosidase gene / hydrolase gene XTH2 were obviously induced to express,while xyloglucan transglycosidase gene / hydrolase gene XTH1,XTH3,XTH4,XTH5 Drop expression.Among these genes,the xyloglucan transglycosidase gene / hydrolase gene XTH2 is expressed most strongly,and it is induced and expressed in four coconut varieties,and the differential expression factor is as high as 5 times.Coconut may express the XTH2 gene of xyloglucan transglycosidase / hydrolase gene in a large amount to make the coconut cell wall more compact,thereby enhancing salt tolerance.3.ABC transporter G family genes ABCG2,ABCG3 and potassium channel protein gene AKT have higher expression levels than other transporter differentially expressed genes,maintaining the balance of Na + and K + concentrations inside and outside the cell may be important for coconuts to respond to salt stress means.4.Among the genes related to active oxygen scavenging substances,the peroxidase genes POD1,POD2,POD3,POD4,POD5,POD6 and glutathione transferase GST1,GST2,GST3,GST4,GST5 were all significantly induced and expressed.In particular,the FPKM of glutathione transferase GST2 reaches more than 4000.Flavonoids can also remove active oxygen in plants.In the flavonoid biosynthesis pathway,the differentially expressed genes CHS,CHI,F3 H,ANR,LAR,LDOX,DFR,FLS,etc.related to flavonoid biosynthesis and flavonoid metabolites Naringin chalcone,epicatechin,myricetin,quercetin,kaempferol,dihydrokaempferol,galangin,afatechin,geranium,dihydroquercetin,epigallocatechin Tea,cyanidin,anthocyanin,gallate,catechin,holy phenol,naringenin,apigenin,luteolin,phlorizin,dihydromyricetin,etc.all have high expression levels and are similar The synthase gene corresponding to flavonoid metabolites also has a consistent trend.In addition,the chalcone synthase genes CHS1,CHS2,CHS3,dihydroflavonol reductase gene DFR and colorless anthocyanin reductase LAR were all induced by their upstream activated differentially expressed transcription factors MYB1 and TT2.The colorless anthocyanin reductase LAR has the highest FPKM value,reaching more than 700.And among the flavonoids,the expression of acatechin,which is produced by colorless anthocyanins,is the largest,and the peak area reaches 8.It can be seen that flavonoids play an important role in coconut response to salt stress.