Research On Response Of Dendrobium Sinense To Drought Stress

Dendrobium sinense is a perennial epiphyte of Dendrobium,which is endemic to Hainan.Drought is an important abiotic stress that restricts the growth of epiphytic orchids.Hainan Island has a typical tropical monsoon climate with distinct dry and wet seasons.Compared with terrestrial plants,epiphytes in this region are under moderate drought stress most of the time.D.sinense has evolved its unique drought-tolerant characteristics and survival strategies in a long-term environment of alternating dry and wet conditions.Up to now,the physiological and biochemical characteristics of D.sinense under drought stress have not been reported.In this paper,the nutritional value was evaluated firstly.Then the physiological indexes of D.sinense plants treated with different gradients of relative air humidity(RH≥95%;45% ≤RH≤50%;RH≤5%);Finally,third generation sequencing,Illumina sequencing and metabolome detection were used to identify the differentially expressed genes(DEGs)and differential metabolites of D.sinense under drought stress,and the biosynthetic pathways related to D.sinense in response to drought stress were explored.It provides new ideas for the future drought-tolerance breeding and genetic information improvement of D.sinense,provides basic research on the introduction and domestication of wild epiphytic orchidaceae plants and the conservation of endangered orchidaceae plants,and provides reference for improving the biological accumulation of medicinal plants.Below are key research findings:(1)Evaluation of nutritional value of D.sinenseThis study detected that D.sinense contains 17 kinds of amino acids and 7 essential amino acids;The polysaccharide content was 277.85 mg / g,which is 1.5,2.5 and 1.3 times of D.huoshanense,D.nobile and D.candidum.The nutritional value membership function score and amino acid score were 26.28% and 49.58%,respectively.D.sinense has high nutritional value;(2)Identification and screening of metabolites of D.sinense under drought stressThis study detected 856 metabolites and 391 differential metabolites(FC≥2 or FC≤0.5,VIP> 1),including flavonoids,amino acids and their derivatives,organic compounds and their derivatives,phenylpropanoid,and lipids.There are many different metabolites in the class and other substances;among them,the DSA vs DSB grouping screened out 5highly significant metabolites(FC> 2000,VIP> 1.7)which are Acetosyringone;4-methylcatechol;pyrocatechol;parthenolide 6-C-hexosyl-8-C-hexosyl-O-hexoside,the significantly different metabolites in the DSA vs DSB group are c-hexosyl-apigenin c-pentoside;acetosyringone;magnolol;catechol;4-methylcatechol;pyrocatechol.(3)Identification and screening of differential genes of D.sinense under drought stressIn this study,combined with third-generation sequencing and second-generation sequencing technologies,18.41 G Polymerase Read Bases and 72969 unigenes were obtained;642 DEGs(|log2 FC| ≥1 and FDR<0.05)and 28 differentially expressed TFs were selected.DEGs are involved in the biosynthesis of metabolites,antioxidant reactions and osmotic adjustment,respectively.(4)Co-expression network and metabolic pathways of D.sinense under drought stressThis study combined the transcriptome and metabolome data with the Pearson correlation coefficient to obtain 121 DEGs and 239 differential metabolites with strong correlation(R2>0.8,DFR<0.05).Using cytoscape software to construct a co-expression network including 33 extremely significant DEGs and 11 differential metabolites.In addition,a total of 5 metabolic pathways related to drought stress were obtained in this study,namely glycerophospholipid metabolism(ko0564),arginine and proline metabolism(ko0330),purine metabolism(ko0230),tryptophan metabolism(ko0380)and phenylpropanoid biosynthetic pathway(ko0940).Among them,purine metabolism and phenylpropanoid biosynthesis pathway are the two most critical biosynthesis pathways of D.sinense in response to drought stress.