Evolutionary Characterization Analysis Of SIAMESE-Related Family Genes And Functional Identification Of Candidate Genes In Maize

Maize is one of the most important food crops.The development of endosperm and the coordination of source,reservoir and flowhave a great impact on maize yield.The endoreplication activity of endosperm cells is important for cell differentiation,grain formation and environmental stress,and is a key driving force for grain development.Previous studieshave shown that the SMR gene is a type of endoreplication related regulatory factor currently only found in plants,which regulates the process of cell-to-endoreplication from mitosis,in order to explore the basic information of the structure and evolution of the SMR gene family in maize,and the biological function of this family in the process of endoreplication in maize,in this study,the SMR gene family members of maize were identified and analyzed by common bioinformatics methods such as keyword search,sequence alignment and evolution analysis.The tissue expression specificity in maize and the expression patterns under different abiotic stresses were detected by RT-qPCR technique,and two of the family members ZmSMR3 and ZmSMR12 were finally cloned and functionally verified.The main results are as follows:1.Among the 12 ZmSMR protein sequences presumed in this paper,there are reported Motifs related to endoreplication,whichhave the function of regulating plant endoreplication.During the 5-10 DAP and 20-25 DAP of seed endosperm development,the gene familyhashigher expression levels,which may be involved in regulating grain filling at this stage.At 15 DAP,members of the ZmSMR gene family may attenuate the inhibition of S-phase CDKA activity at this time through low levels of expression,thereby regulating the endoreplication of maize endosperm cells at ahigher level.In addition,the expression characteristics of ZmSMR gene family in roots,stems,stem nodes and leaves of maize showed diversity,but all membershadhigher expression levels in both ears and tassels,which were involved in regulating the growth and development of maize reproductive organs.2.Members of the ZmSMR gene family respond to a variety of abiotic stresses,but each member responds to at least one stress condition.The transcription level of ZmSMR11 washigher than that of the control under all stress treatment conditions except for low temperature stress.The expression level of ZmSMR10 was lower than that of the control in almost all stress treatments,and only the expression was up-regulated at 24 h under 20% PEG stress,and contributed less to the tolerance of abiotic stress in maize.ZmSMR1,ZmSMR2,ZmSMR8,ZmSMR9 and ZmSMR11 mayhelp to improve the adaptability of maize inhightemperature environments,thus contributing to the increase in maize yield.ZmSMR2 can also be induced by salt stress and low temperature stress,which can increase the tolerance of maize to salt stress and low temperature,while ZmSMR1 and ZmSMR5 may play an important role in enhancing tolerance to salt and drought stress.Both ZmSMR9 and ZmSMR12up-regulated gene expression under 100 umol/L ABA and 200 mmol/L NaCl stress,which could increase the tolerance of maize to these two abiotic stresses.In addition,whether ZmSMRs respond to abiotic stress is related to whether or not a corresponding promoter element is contained.3.Overexpression of ZmSMRs increased the ger mination rate of Arabidopsis thaliana under 8 μmol/L ABA conditions.Overexpression of ZmSMR3 increased the adaptability of Arabidopsis thaliana root growth under ABA conditions,while ZmSMR12 overexpressing transgenichomozygote was sensitive to ABA stress.In addition,overexpression of ZmSMRs affected the vegetative and reproductive growth of Arabidopsis thaliana.The ZmSMR3 and ZmSMR12 overexpressing transgenichomozygotes were significantly smaller than the wild type Arabidopsis thaliana,the number of rosette leaves was reduced,and the length and width ofharvested seeds were significantly improved.Overexpression of ZmSMR3 and ZmSMR12 also significantly increased the level of endoreplication in Arabidopsis leaves,indicating that it is indeed involved in the regulation of the internal replication process.