Physiological Response And Transcriptome Analysis Of Emmenopterys Henryi Oliv. Under High Light Stress

To investigate the physiological and molecular response mechanisms of Emmenopterys henryi Oliv.to high light stress,this paper used Emmenopterys henryi Oliv.as materials and a light intensity of 54μmol·m^-2·s^-1as the control,and studied the changes in growth indicators,photosynthetic gas exchange parameters,chlorophyll fluorescence parameters,and abscisic acid content of Emmenopterys henryi Oliv.under high light conditions(108μmol·m^-2·s^-1,180μmol·m^-2·s^-1,and 270μmol·m^-2·s^-1).Transcriptome analysis was performed using RNA-seq technology to screen differentially expressed genes under high light stress and conduct functional expression analysis.The main research results are as follows:（1）.High light stress led to yellowing of the leaves of Emmenopterys henryi Oliv.,an increase in the root crown ratio,and a decrease in water content.The content of chlorophyll and carotenoids decreased,while the content of anthocyanins increased.（2）.High light stress significantly altered the photosynthetic gas exchange parameters and chlorophyll fluorescence parameters of young seedlings of Emmenopterys henryi Oliv.Net photosynthesis rate（Pn）,stomatal conductance（Cond）,and transpiration rate（Tr）decreased,while intercellular carbon dioxide concentration（Ci）increased.The maximum photochemical efficiency of PSII（Fv/Fm）,potential activity（Fv/Fo）,actual photosynthetic efficiency[Y（II）],non-photochemical quenching coefficient（NPQ）,photochemical quenching coefficient（q P）,and electron transport rate（ETR）decreased,while regulatory energy dissipation quantum yield[Y（NPQ）]and non-regulatory energy dissipation quantum yield[Y（NO）]increased.（3）.High light stress caused damage to the membrane structure of the Emmenopterys henryi Oliv.,leading to a significant increase in leaf conductance and acetaldehyde（MDA）content.（4）.High light stress caused a significant increase in abscisic acid（ABA）content of Emmenopterys henryi Oliv.（5）.The transcriptome analysis results showed that under high light stress,there were6776 differentially expressed genes in Emmenopterys henryi Oliv.,including 3063upregulated genes and 3713 downregulated genes.Based on the GO functional enrichment analysis,the upregulated genes（2022 in total,with 196 significantly enriched）and downregulated genes（1835 in total,with 129 significantly enriched）were mainly enriched in the biological processes,molecular functions,and cellular components categories.The KEGG pathway enrichment analysis indicated that all differentially expressed genes were enriched in20 metabolic pathways,including the biosynthesis and metabolism pathways of secondary metabolites,photosynthesis,etc.Among these metabolic pathways,the expression levels of genes related to photosynthesis,such as Lhca4,Lhcb1,Lhcb2,Lhcb5,psaA,psaE,psaG,psaH,psaK,psaL,psaO,psbC,psbK,psbO,psbP,psbQ,psbR,psbW,petA,petC,petG,petE,atpC1,atpI,RBCS,rbcL,RCA,HEMA1,and PORA,as well as genes related to abscisic acid synthesis and signaling pathways,such as NCED1,NCED3,CYP707A,and PP2C51,were significantly down-regulated.Conversely,the expression levels of genes related to photosynthesis,such as psbS,atpA,and atpD,as well as genes related to anthocyanin synthesis,antioxidant enzymes,and abscisic acid synthesis and signaling pathways,such as BGLU11,BGLU46,BGLU23,BGLU24,BGLU34,PYR/PYL,and SnRK2C,were significantly up-regulated.The qRT-PCR varification results showed that the expression levels of 8selected differentially expressed genes were consistent with the RNA-seq results.In summary,Emmenopterys henryi Oliv.mainly responds to high light stress via regulating photosynthesis,antioxidase systems,abscisic acid metabolism and signal pathway,as well as anthocyanin metabolism pathway.