Deciphering Mechanism Underlying Heterosis And Water-logging Tolerance In Maize Hbyrid ‘longping206’ By Genome-wide Transcriptome Analysis

’longping 206’is a spreading maize hybrid in South Areas of the Yellow River,Huai and Hai Rivers in China with conspicuous growth heterosis and higher yield production.Moreover,it also has some tolerance to water-logging stress which is different from other numerous maize varieties.Maybe these two important features make the hybrid to spread quickly in South Areas of the Yellow River,Huai and Hai Rivers.Most researches were focused on the fitness of origin cultivation and agronomic traits with less in molecular biology.Here,we selected the maize variety’longping206’to explore the potential molecular mechanism for heterosis and water-logging tolerance through high-throughput RNA-sequencing（RNA-seq）.The main conclusions of this study are as follows:（1）In the transcriptome analysis of heterosis,3005 DEGs existed concurrently in longping206 and parents.1788 DEGs were up-regulated in hybrid,925 up in parents.The most expression pattern of DEGs was dominance expression pattern（76%）including high-parent level and low-parent level.Next is over-dominance expression pattern（23%）including above high-parent level and below low-parent level.（2）Gene Ontology analysis was used to classify the function of DEGs.Most of important biological processes were enriched in hybrid such as signal transduction,carbon metabolism,energy transfer,stress threaten,protein phosphorylation and so on.They will provide significant support for heterosis of longping206.Kyoto Encyclopedia of Genes and Genomes（KEGG）database was performed to analyze the pathway which the DEGs were involved and enriched.Starch and sucrose metabolism and plant hormone signal conditioning were enriched in longping206.The DEGs which involved in these pathways were up-regulated indicated the importance of these pathways to the formation of heterosis.（3）The biosynthesis and degradation of carbohydrate in hybrid told us that the DEGs related to sucrose were active which will accumulate the dry matter in hybrid and provide the energy to other biological processes.For another,the DEGs related to cellulose active will furnish the material basis for the faster cell division and protect the cell in hybrid.It will explain the reason why longping206 has a better phenotype than its parents.Most of the DEGs related to plant hormones were up-regulated.It may make the longping206possess more hormones contents than inbred lines.Longping206 had the heterosis because of the addition synergistic effect of all hormones.（4）In the transcriptome analysis of water-logging,the data indicated that the water-logging caused 3033 genes significant changes in mRNA abundance with 1550up-regulated in handle group,1483 up in control group;gene ontology analysis revealed that water-logging stress inhibited photosynthesis,H₂O₂ decomposition,carbohydrate synthesis and ethylene synthesis,but promoted the responses to low oxygen,ROS-scavenging and anaerobic respiration.The results have proved these biological processes were the important role to water-logging acclimation in maize.Although the molecular mechanisms of heterosis and water-logging tolerance are complicated particularly,the results in our study still have important signification to understand the molecular mechanism of heterosis and water-logging tolerance.It can provide useful molecular resources and candidate genes for another research.