Identification Of Transcription Factors Of Populus Euphratica Oliv. Heteromorphic Leaves And Their Role Of The Leaf Morphogenesis

Populus euphratica Oliv.is the only natural arbor tree species that grows in the desert area,it has typical heterophylly.In this study,based on the third-generation sequencing technology,a large number of transcription factors were identified in the linear leaves(Li),lanceolate leaves(La),ovate leaves(Ov)and broade-ovate(Bo)of Populus euphratica Oliv.(P.euphratica)with four specific leaves at different development stages.To study these transcription factors(TFs)in the role of the morphogenesis of Populus euphratica Oliv.heteromorphic leaves(P.hl),not only we analyzed the expression profiles of these transcription factors in the Li,La,Ov and Bo of P.euphratica,but also based on the competitive endogenous RNA hypothesis,we also found that these TFs were also regulated by non-coding RNA.Especially,the SPL transcription factor family might play an important role in the morphogenesis of P.euphratica leaves.The main results are as follows:(1)Almost all young leaves are Li in P.euphratica,which gradually change into Bo with the development of the leaf shape.In this process,the leaf length and index gradually decreased with the progressive development stage,while the leaf width gradually increased with the development stage.(2)2132 differential candidate TFs were identified in the P.hl.Among them,28 new TFs were found to be differentially expressed.Based on the consistency of expression pattern of transcription factors and leaf polarity,we finally identified 118 TFs related to the morphogenesis of P.hl.The GO annotation indicated these TFs could be involved in various biological functions such as metabolic processes,regulating leaf morphological development,signal transduction,salt stress and regulating changes in hormone content in the P.hl.Moreover,while transcription factors regulated leaf shape development,they were also affected by non-coding RNA.Especially,this research demonstrated the presence of circRNAs related to TFs in the P.hl for the first time,and the interaction between TFs,circRNA,and miRNA jointly regulated the morphogenesis of P.hl.Therefore,the morphogenesis of P.euphratica leaves is not only affected by external environmental factors,alsoregulated by the complex regulation mechanism in vivo;thereby it confirmed the important role of TFs in the morphogenesis of P.hl.(3)We identified and characterized 33 SPL transcription factors in the P.hl,and their expression patterns showed that most of the SPL TFs were down-regulated expression in Li and up-regulated expression in Bo;while the expression patterns were basically identified in the La and Ov.Through phylogenetic relationships,we found that P.euphratica SPL transcription factor(PeuSPL)has high homology with Arabidopsis SPL TF.Conservative domain analysis showed that there was functional differentiation of SPL TFs in P.hl.In addition,miR156 has been found to regulate the expression of SPL TFs in the P.hl.At the same time,there existed complex regulatory mechanisms of ceRNA(circRNA,lncRNA)-miR156-SPL,but these regulatory pathways were mainly involved in regulating the expression of SPL TFs in an indirect rather than direct manner,and then participated in the regulation of salt stress,the change of hormone content in leaves,the formation of leaf polarity,leaf development,the transition from juvenile vegetative phase to reproductive phase,signal transduction and photosynthesis of P.euphratica leaves and other biological functions to affect the morphogenesis of P.euphratica leaves.In this study,we started with four specific leaf characteristics of P.euphratica to study the role of TFs in P.hl,through bioinformatics analysis,we identified and characterized 2132 differentially expressed transcription factors in P.hl,of which 118 transcription factors are closely related to the morphogenesis of P.euphratica leaves,and could be involved in the formation of different polarities of P.euphratica leaves.Furthermore,these TFs might be regulated by non-coding RNA while regulating the morphological development of P.euphratica leaves.It has been confirmed that circRNAs can affect the expression of transcription factors in P.euphratica leaves by deceiving miRNAs in this study,therefore,our results provide a basis for further studies of leaf morphogenesis in plant.