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1、ThePlantCell,Vol.23:431–442,February2011,www.plantcell.orgã2011AmericanSocietyofPlantBiologistsREVIEWEvolutionandFunctionalDiversificationofMIRNAGenesJoshT.Cuperus,a,b,c,1NoahFahlgren,a,b,c,1andJamesC.Carringtonb,c,2aMolecularandCellularBiologyProgram,Orego
2、nStateUniversity,Corvallis,Oregon97331bDepartmentofBotanyandPlantPathology,OregonStateUniversity,Corvallis,Oregon97331cCenterforGenomeResearchandBiocomputing,OregonStateUniversity,Corvallis,Oregon97331MicroRNAs(miRNAs)aresmallregulatoryRNAsfoundindiverseeu
3、karyoticlineages.Inplants,aminorityofannotatedMIRNAgenefamiliesareconservedbetweenplantfamilies,whilethemajorityarefamily-orspecies-specific,suggestingthatmostknownMIRNAgenesaroserelativelyrecentlyinevolutionarytime.GiventhehighproportionofyoungMIRNAgenesin
4、plantspecies,newMIRNAfamiliesarelikelyspawnedandthenlostfrequently.Unlikehighlyconserved,ancientmiRNAs,youngmiRNAsareoftenweaklyexpressed,processedimprecisely,lacktargets,anddisplaypatternsofneutralvariation,suggestingthatyoungMIRNAlocitendtoevolveneutrall
5、y.Genome-wideanalysesfromseveralplantspecieshaverevealedthatvariationinmiRNAfoldbackexpression,structure,processingefficiency,andmiRNAsizehaveresultedintheuniquefunctionalityofMIRNAlociandresultingmiRNAs.Additionally,somemiRNAshaveevolvedspecificpropertiesan
6、dfunctionsthatregulateothertranscriptionalorposttranscriptionalsilencingpathways.TheevolutionofmiRNAprocessingandfunctionaldiversityunderscoresthedynamicnatureofmiRNA-basedregulationincomplexregulatorynetworks.INTRODUCTIONKuriharaandWatanabe,2004;Kuriharae
7、tal.,2006).Thespe-cificsofmiRNAprocessinginplantsaresomewhatlesswellMicroRNAs(miRNAs)areaclassofsmallRNAsfoundinplants,understood.Inthemajorityofcases,DCL1firstcatalyzescleav-animals,andotherdiverseeukaryotesaswellasanumberofageofthefoldbackattheloop-distals
8、ide,andsubsequentlyonDNAviruses.PlantmiRNAsrangeinsizefrom20to24nucle-theloop-proximalside,ofthemiRNA/miRNA*region,inase-otidesandmediategenesilencingattheposttranscriptionalquentialmannerlikethatinanimals(Ku
