AP2/ERF Transcription Factors ERF?-1 And ERF?-2 Of Arabidopsis Regulate Plant Lateral Roots Growth And Development

Roots are essential for plants to perception and uptake water and nutrients,anchorage of plant,store nutrients,and vegetative reproduction.The root system is composed of two types:one is the primary root,which was formed by the radicle development;the other roots were formed post-embryonically,including lateral roots and adventitious roots.Lateral roots formed as branches from the primary root,and adventitious roots developed from shoots,stems or leaves.The formation and development of lateral roots play a decisive role in the root system architecture.Therefore,the study of lateral roots is of great significance for understanding the regulation mechanism of plant root growth and development and crop production based on root structure improvement.The root system of Arabidopsis thaliana is relatively simple.At present,the initiation and development of lateral roots of model plant Arabidopsis thaliana have been studied in detail.The production of lateral roots is from primary roots.This process is regulated by many factors,such as internal hormone signals and external environmental signals.As a key regulator of root development,auxin plays important roles in controlling root development and architecture of the root system.Auxin also interacts with other hormones to regulate lateral root growth and development.Auxin synthesis,polar transport and signal transduction are involved in the regulation of lateral root growth and development.Among them,ARF7/19-LBDs mediated auxin signaling pathway is the most thorough and clear lateral root regulation pathway.In order to further elucidate the regulatory factors of lateral root growth and development,and to further elucidate the molecular mechanism of auxin regulating lateral root development.Two genes encoding AP2/ERF transcription factors,ERF?-1 and ERF?-2,were isolated by screening the expression profiles.Phenotypic analysis showed that overexpression of ERF?-1 or ERF?-2 significantly reduced the emergence density of lateral roots,while mutation of ERF?-1 or ERF?-2 significantly increased the emergence density of lateral roots.These results suggest that ERF?-1 and ERF?-2 is involved in the regulation of lateral root development.Further studies showed that auxin-induced transcriptional expression of ERF?-1 and ERF?-2 was not regulated by ARF7/19-LBDs.Moreover,the expression of key genes in auxin signaling pathways such as ARF7,ARF19,IAA3,LAA14,LBD16,LBD17,LBD18 and LBD29 did not change significantly in ERF?-1 and ERF?-2 overexpression and ERF?-1-SRDX and ERF?-2-SRDX lines,suggesting that the regulation of ERF?-1 and ERF?-2 on lateral roots may not be achieved by affecting the transcriptional expression of these genes.In order to explore the mechanism of ERF?-1 and ERF?-2 regulating lateral root development,total RNA of seedling roots of wild type Col,ERF?-1 and ERF?-2 overexpression and ERF?-1-SRDX and ERF?-2-SRDX plants were extracted for transcriptome sequencing.Through the analysis of sequencing data and quantitative validation of related genes,we selected WAKL4,KCS16,MYBL2,PMAT2 and CAPE3 genes which were significantly regulated by ERF?-1 and ERF?-2 for further analysis.After NAA treatment,the expression of WAKL4,KCS16 and MYBL2 were up-regulated,while the expression of PMAT2 and CAPE3 were down-regulated,suggesting that these five genes are responsive to auxin.Phenotypic analysis of wakl4,pmat2 and cape3 mutants revealed that WAKL4 promote lateral root emergence,while PMAT2 and CAPE3 inhibit lateral root emergence.KCS16 and MYBL2 are expressed in the lateral root primordia,suggesting that KCS16 and MYBL2 may be involved in the regulation of lateral root development.These results indicate that ERF?-1 and ERF?-2 may regulate the emergence of lateral roots through regulating these five downstream genes.ERF?-1 and ERF?-2 are transcription factors of the AP2/ERF family,which play important roles in plant physiological processes and response to many stresses.At present,the functions of some members of the AP2/ERF family have been studied in detail,however,there are few studies on the regulation of lateral root development.This study helps to deepen the understanding of lateral roots development and the functions of transcription factors of AP2/ERF family.