Identification And Evolutionary Analysis Of MORC Gene Family In Green Plants

MORC(Microrchidia)gene is a highly conserved nuclear protein-coding gene,which is involved in the regulation of transcriptional gene silencing and immune defense in plants as a novel epigenetic regulator.Generally,MORC proteins contain a hallmark GHKL-type(Gyrase,Hsp90,Histidine kinase,MutL)ATPase module in their N-terminus,which can affect the regulation of gene expression.Currently,MORC proteins have been identified in both animals and plants,among which four and seven canonical MORC family members have been identified in humans and Arabidopsis,respectively.In order to deeply understand the evolutionary process of the MORC gene family,the evolutionary history of the MORC gene family and the sequence characteristics of MORC protein in plants and animals were investigated by means of bioinformatics and phylogenetic analysisIn this study,83 and 356 candidate MORC proteins were identified in 27 animal and 60 plant genomes,respectively.At the same time,based on the transcriptome-based protein sequence,we also identified 154 candidate MORC proteins from 56 non-flowering plants.Large-scale MORC sequence motif analysis revealed the presence of a highly conserved motif composition that defined as the MORC domain.The sequence of the MORC domain is conservative and contains several typical protein secondary structural elements,which can be used to identify the MORC gene in other speciesThe phylogenetic tree constructed using these MORC proteins in plant and animal lineages showed that the MORC gene family was clearly divided into two major groups,named Plants-Group I,Plants-Group II and Animals-Group I,Animals-Group II,respectively The MORC domain was present in both animals and plants,indicating that it originated in the common ancestor before the divergence of animals and plants.In addition,we further studied the phylogenetic relationships and gene expansion mechanism of the MORC gene family in green plants,and found that most MORC gene was expanded in angiosperms.Based on the collinear evidence between duplicated gene pairs,most of the expansion in angiosperms was caused by segmental duplication or genome-wide duplication events.Among them,the Plants-Group I could be further subdivided into Group I-1 and Group I-2 Group I-1 contained only the MORC gene in seed plants,while the Group I-2 contained whole green lineages MORC gene,which indicated that Group I-1 and Group I-2 divergence occurred at least before the emergence of spermatophytes.MORC gene was expanded largely in both Group I-2 and Group II,but relatively conservative in Group I-1.The motif pattern of MORC protein was relatively conservative in each groups and the intron-exon composition of MORC gene in each groups was also roughly consistent.In order to explore the expression divergence of duplicated MORC gene pairs,we analyzed the expression patterns of MORC genes in Arabidopsis,soybean and rice,respectively.It was found that MORC gene was mainly expressed in reproductive tissues compared with vegetative tissues,and showed divergent expression patterns for several paralogous gene pairs,indicating that MORC gene may play an important role in the development of reproductive tissuesIn conclusion,this study uses bioinformatics,comparative genomic and phylogenetic methods to systematically elucidate the origin,classification and phylogenetic relationships of the MORC gene family in animals and plants,and defines the MORC domain as a conserved feature for MORC gene identification.Furthermore,the evolutionary pattern and expansion mechanism of the MORC gene family in green plants,as well as the analysis of MORC gene expression pattern,may be helpful to further reveal the functional mechanism of MORC gene in epigenetic regulation.