MicroRNA Transcriptomic Analysis Of Heterosis At Rice Seedling And Young Panicle Stages

Rice(Oryza sativa)is one of the most important crops,especially using the hererosis to improve rice yeild play an inportant role.The molecular mechanism of heterosis is very important to rice molecular breeding,but still be mysterious In this study,of the widely used restorer line Shuhui527(SH527)and its offspring introgression line WD7 testcrossed with a sterile Xieqingzao A(XA)to produce two hybrid combinations.And F1(XA / SH527)was considered as higher yield heterosis combination than F1(XA / WD7)by years’ tests.These five materials were conducted phenotypic evaluations at the seedling stage and young panicle stage,high-throughput sequencing technology and bioinformatics analysis were conducted based on the principle of Solexa,differentially expressed miRNAs and its target genes were identified in both two stages,combining with phenotypic data and previous research findings,the results obtained are as follows.First,at seedling stage(especially the four-leaf stage),the two hybrids had higher trait value than the corresponding mid-parents value in chlorophyll content,white root number,white root length,stem height,leaf length,leaf width,fresh weight and dry weight of upper organs.Therefore,F1(XA / SH527)displayed higher leaf length,leaf width,shoot fresh weight and dry weight of upper organs than F1(XA / WD7).And in the early tillering stage,the tillers of F1(XA / SH527)are more than F1(XA / WD7)’s.Second,two-year average yield performance of the two hybrids and their parentsis: F1(XA / SH527)> SH527> F1(XA / WD7)> WD7> XA,and the same trend was observed in filled-grain number per panicle.For spikelet fertility,the trend was list asSH527> WD7> F1(XA / SH527)> F1(XA / WD7)> XA.Third,all RNA(known and unknown)types are more in young panicle stage than in the seedling stage,and known species of miRNA species showed an opposite conclusion through the high-throughput sequencing.The total numer of the known miRNA,found in F1(XA / SH527)and its parents,is 361 at seedling stage and is 328 at young panicle stage.The total numer of the known miRNA,found in F1(XA / WD7)and its parents,is 356 at seedling stage and is 314 at young panicle stage.Fourth,comparing two hybrids and their corresponding mid-parents value,we found that the mode of action of miRNA was non-additive and additive expression,non-additive expression is the main action.In non-additive expression,above high-parent and below low-parent expression account most part.Fifth,79 significantly differently expression miRNAs of 5 materials were identified at same stage,and we predicted their target genes by using the online software psRNATarget,found 477 target genes.GO functional annotation showed that most of the target genes weretranscription factors,some target genes were involved in enzyme activity and metabolic pathways including signal transduction,transcription and translation,material and energy metabolism,stress and so on.Sixth,the male parent plays an important role in the formation of heterosis.Comparingthe mid-parents values of the parents with two hybrids,five DEM families were identified including MIR395,MIR397,MIR398,MIR408,and MIR528 families,they showed down-regulate expressionwhich indicating that MIR395,MIR397,MIR398,MIR408,MIR528 may be involved in the process of heterosis.These results above suggested that miRNA can regulate genes expression,thus ultimately lead to the formation of heterosis.