| During maize growth and development,root system is responsible for water absorption and mineral elements acquirement,the growth of maize root condition directly determine the growth of the corn.Thus,to identify the relative genes and reveal their molecular mechanisms in root development,which will provide new genetic resources for improving maize root architecture and promoting grain yield in germplasm innovation research.AUX/IAA gene family plays an important role in auxin signal transduction.It’s involved in plant cell elongation,root and bud development and other plant physiological and biochemical processes.The gene family and its functions have been studied in detail in Arabidopsis,but relatively little in maize.Through the evolutionary analysis of the maize AUX/IAA gene family,this paper explored the key gene of the AUX/IAA family that influenced root development and analyzed its function and regulation mechanism.The main results as follows:1.Through the evolution analysis of 40 genes in maize AUX/IAA family,a subfamily branch was discovered.Thus,we cloned 7 genes of this subfamily and transformed them into Arabidopsis.It was found that ZmLRR1 gene could inhibite the growth of Arabidopsis root,and speculated this gene might involved in regulate root growth and development.Tissue expression pattern analysis showed that ZmLRR1 gene was highest expressed in young seedling roots and induced by IAA in maize.2.Overexpression of ZmLRR1 gene in maize found that the number of lateral roots on primary roots and seminal root decreased obviously,which resulted in a decrease in the overall number of over-expressed maize roots.While the number of lateral root on primary and seminal roots in mutants increased significantly,and the number of crown roots also increased,indicating that ZmLRR1 mainly regulated lateral root development in maize roots.3.The results of protein interaction analysis showed that ZmLRR1 protein interacted with auxin response factor ZmARF5 in vivo or in vitro,and the root number of the zmarf5 mutant plants were significantly fewer than that of the wild type,especially the number of lateral roots on the seminal roots decreased significantly,indicating that ZmLRR1 gene regulated root development by interacting with ZmARF5 and together controlled the transcription of downstream genes.4.ZmLRR1 gene overexpression or knockout caused the expression level of auxin response factors,auxin transport genes and relative cell division genes significantly changed,which indicated that the development and growth of roots were mainly affected by the expression level of auxin transport and response genes.The results of promoter structure analysis and yeast one-hybrid results proved that the ZmARF5 gene could bind the AuxRE element of ZmPIN3 gene and ZmCYCB2;1 gene promoter,indicating that the ZmARF5 gene could directly regulate the expression of the auxin transport gene ZmPIN3 and the cell division gene ZmCYCB2;1.5.ZmLRR1 gene could inhibite the apical transport of auxin in Arabidopsis roots,resulted in highly auxin content in the vascular bundle and increased cell division,but the division was abnormal and the lateral root primordium cannot be formed,it could also reduce the auxin distribution of the lateral root primordium and root tip of Arabidopsis.The above results eventually led to the reduced lateral root and shorter primary root in over-expression Arabidopsis.6.Lateral root primordial staining analysis showed that the overexpressing lines had fewer lateral root primordia than the wild type,while the lateral root primordia of the mutant increased significantly,the cross-section cells of the crown root showed the root primordia of the overexpressing plant was developed slowly,and the number was less than that of the wild type,while the lateral root primordia of the mutant developed faster and the number was slightly more than that of the wild type.These results indicated that ZmLRR1 gene affect the maize roots growth by regulating the formation of maize root primordia.The above results indicated that the ZmLRR1 gene playing a crucial role in regulating the growth and development of plant roots.Mainly through the interaction with the auxin response factor ZmARF5 to regulate the expression level of downstream auxin transport genes and cell division genes,affecting the distribution of auxin transport and the formation of lateral root primordia,eventually regulating the growth and development of the lateral roots in maize. |
