Identification Of Purple Acid Phosphatases (PAPs) Genes In Tea Plants And Poplar And Their Expression Responses To Phosphorus Deficency And Excess Iron

Purple acid phosphatases(PAPs)are metallohydrolases that use a binuclear metal ion center to catalyze the hydrolysis of a broad range of phosphorylated substrates.The heterovalent active site(Fe(III)-M(II),where M = Fe,Zn,or Mn)is essential for all active PAPs for catalysis.PAP encoding genes are a multigene family,which are involved in diverse biological functions,including maintaining mineral nutrient homeostasis.However,roles of PAPs in most woody plants for the homeostasis of phosphorus and iron remain unclear.In this study,the PAPs encoding genes was identified in both tea plant(Camellia sinensis)and poplar(Populus trichocarpa)through genome-wide investigation,and their phylogenetic relationships were analyised.We also explored the expression patterns of CsPAPs genes in response to excessive Fe supply,as well as that of PtPAPs to phosphorus deficiency,for an attempt to contribute to further understanding of the PAPs genes’ function in plant phosphorus and iron nutrition.It will be helpful for the cultivation and improvement of crops with phosphorus and iron efficiency.The main research results are as follows:1.19 CsPAPs members in tea plant and 35 PtPAPs members in poplar were identified based on BLAST alignment and conserved motifs in the genome-wide database.Phylogenetic analysis clustered plant PAPs into four major groups,of which group II contained two specific cysteinecontaining motifs “GGECGV” and “YERTC”.It suggests that members of group Ⅱ may have unique substrate selectivity or catalytic activity and thus perform different physiological functions.2.RNA-sequencing(RNA-seq)analyses showed that most CsPAPs expressed in both roots and leaves,and the abundance of some CsPAPs were different between roots and leaves,indicating that they are necessary for maintaining basic cellular functions,and may be involved in dynamic adjustment during plant development.When supplied with excess Fe,the expression levels of four genes were significantly changed.Of which,CsPAP15 a,CsPAP23 and CsPAP27 c were shown as downregulated,while the highly expressed CsPAP10 a was upregulated,implicating that some CsPAPs genes could be associated with the responses of tea plants to the iron regime.3.The expression patterns of PtPAPs in different organs of poplus under normal and phosphorus deficieny conditions were analyzed by qPCR,showing that PtPAPs have different tissue expression specificity,indicating that they maintained different tissue functions during plant growth.The expression of PtPAPs is affected by phosphorus deficiency,and 13 PtPAPs were defined as DEGs.The root is the major tissue responsing to phosphorus deficiency,of which,the most variable PtPAP17 b and PtPAP12 b are more than 12 times higher than normal controls,suggesting that these PtPAPs gene are involved in the response to phosphorus deficiency in poplar and play important roles.PtPAP17 d and PtPAP17 b are two genes expressing high in all parts except stem,while some PtPAPs only expressed in specific tissues,indicating their specificity of function.10 DEGs PtPAPs contain P1 BS cis-elements,may be regulated by PHR.Group Ⅳ members were differentially expressed under phosphorus deficiency,indicating that the members of the gene family are evolutionarily functionally conserved in different species.In summary,we identified 19 CsPAPs and 35 PtPAPs using bioinformatics methods,and found two specific conserved motifs through phylogenetic analysis.Transcriptional analysis revealed that CsPAPs are involved in the regulation of iron homeostasis when exposed in excess Fe,and PtPAPs play roles in the regulation of phosphorus nutrition.