Identification Of Salt-Tolerant MicroRN As And Their Targets In A Maize Inbred Line

Maize(Zea mays)is one of the most important crops in the world.Small RNAs especially micro RNAs(mi RNAs)play an essential role in responses and adaptation of plants to many stresses including salt stess.Characterizing correlative mi RNAs will improve our understanding of salt tolerance and thus contribute to the sustainable production of maize.In this research,small RNA and degradation sequencing was performed on a maize inbred line(LH196),using,and many mi RNAs and their targets were identified in response to salt stress.The identity of target genes was confirmed by quantitative expression analysis.Furthermore,the interactions between mi R164 a and its target genes were preliminary studied by overexpression and target mimicry under salt treatment in maize.The main results are as follows:1.Compared with CK,maize inbred line LH196 showed obvious phenotypic changes under salt stress,like wilting,withered and yellow leaves,increased aerial roots and lateral roots,decreased biomass,increased cyanine glycosides and root-shoot ratio.2.With Combined analysis of deep sequencing of small RNA and degradome libraries,over 100 million raw reads were generated from the small RNA and degradome sequencing data of four libraries.A total of 1040 known plant mi RNAs were identified from these four maize libraries,with 762 and 726 from leaves and roots respectively,and 448 common mi RNAs were identified from both leaves and roots.A total of 37 potential new mi RNAs were selected on the same criteria in response to salt stress.3.Two novel member,mir-36 and mir-29 were identified belonging to the known Mi R167 and Mi R164 families,respectively.4.Quantitative real time polymerase chain reaction(q RT-PCR)analyses of mi RNAs and their targets showed that eight species of novel mi RNAs may play key roles in response to salinity in maize.5.Four species of novel mi RNAs(mir-205,mir-250,mir-330 and mir-17)are down-regulated under salt stress,and some of their targets were up-regulated.Part of these up-regulated targets belong to transcription factors,whereas some of them were protease or kinase,which were in response to many abiotic stress in previous researches,these may contribute to the elite salt tolerance in the maize inbred lines LH196.6.A possible internal regulation pathway was proposed for four species of maize novel mi RNAs in response to salt stress.7.Zma-mi R164 may respond to salt stress in this way: the expression of zma-mi R164 lowered under salt stress,leading to significant increase of expression in its target genes GRMZM2G114850(NAC transcription factor family proteins,NAM,ATAF,CUC)and GRMZM2G008819(electronic carrier);NAC transcription factors responded to salt stress.through regulating the expression level of downstream genes.