Preliminary Exploration On The Metabolism And Molecular Mechanisms Of Poplar Seedlings Responding To Para-Hydroxybenzoic Acid Stress

Poplar is an excellent landscape tree species in China and is an important woody model plant in molecular biology research.It has important ornamental,ecological and application value.The accumulation of phenolic acids such as para-hydroxybenzoic acid in soil is the main reason for the continuous cropping obstacle of poplar.The study of para-hydroxybenzoic acid resistance is the key to alleviate the continuous cropping obstacle of poplar.In this study,‘84K’（Populus alba×P.glandulosa）was used as the experimental material,and metabolomics and transcriptomics data was analyzed to explore the differential expressed genes,differential metabolites and regulatory network of poplar in response to para-hydroxybenzoic acid stress.The data provides a theoretical basis for alleviating the continuous cropping obstacle of poplar.The main results are as follows:（1）Under 1.5 mmol·L^-1 para-hydroxybenzoic acid stress,the growth of poplar seedlings was significantly inhibited with the prolongation of treatment time.After treatment with para-hydroxybenzoic acid for 6 hours,poplar seedlings showed morphological characteristics of severely curved shoot tips and wilting of the top leaves.（2）Metabolomic analysis showed that 126 differential metabolites were identified in poplar leaves after 6 hours of 1.5 mmol·L^-1 para-hydroxybenzoic acid stress,including 9types of compounds.Among them,the top 3 types of differential metabolites with the largest number were lipids,amino acids and derivatives,nucleotides and derivatives.In addition,we also found that differential metabolites such as lysophosphatidylcholine,lysophosphatidylethanolamine and tyrosine may play an important role in response to para-hydroxybenzoic acid stress in poplar.（3）Transcriptome analysis showed that 11084 differential expressed genes（DEGs）were identified in poplar leaves after 3 hours of 4 mmol·L^-1 para-hydroxybenzoic acid stress.Further analysis showed that these DEGs contained 603 transcription factors,which mainly concentrated in b HLH,AP2/ERF,MYB and b ZIP families.The expression of Pag DREB2 was up-regulated by 3238 times,and this gene was positively correlated with abscisic acid-related synthetic genes（Pag ZEP,Pag NCED,and Pag Crt ISO）,which may play an important role in response to para-hydroxybenzoic acid stress in poplar.In addition,143 DEGs were significantly enriched in plant hormone signal transduction pathways,among which abscisic acid signal transduction pathway is the main signal transduction pathway for poplar in responding to para-hydroxybenzoic acid stress.（4）Combined metabolome and transcriptome data analysis showed that purine metabolism and caffeine metabolism pathways were the main metabolic pathways of poplar in response to para-hydroxybenzoic acid stress.The DEG XDH and differential metabolites 3’,5’-cyclic guanylate and 3’,5’-cyclic adenylate in the above pathways may play a key role in response to para-hydroxybenzoic acid stress in poplar.In addition,poplar may also respond to para-hydroxybenzoic acid stress through amino acid metabolism,glycerophospholipid metabolism and abscisic acid signal transduction pathways,and metabolites such asγ-aminobutyric acid,5-aminolevulinic acid,and abscisic acid in these pathways may play an important role in poplar response to para-hydroxybenzoic acid stress.