Omics Analysis Of Heterosis For Internode Length Under Ear In Maize(zea Mays L)

Maize is the world’s most successful crop which utilizes heterosis. The plant height and ear height in maize showed high heterosis, and always was used as model traits to study the genetic bases of heterosis. Owing to dissecting the genetic bases of plant height and ear height will help us to reveal the mechanism of heterosis, and give a guidance for selecting elite hybrid which has appropriate ear height and resistant to lodging. In biological contruction, the number and the length of different internodes are two main components of ear height, and the length of internode show high heterosis. In this study, four elite commercial hybrids maize and their corresponding parents was choosed as the material, and three internode lengths under ear was used for dissecting the genetic bases of heterosis by means of Solexa sequencing and 2-DE technology method The main conclusions are as follows:1. After analyzing the internodes heterosis of the four elite maize hybrids, we found that different the length of internodes under ear had different heterosis pattern. Compared to its parental lines, the heterosis of the seventh, eighth and ninth internode length under had significant relation with ear height of different hybrids in maize, and the ninth internode heterosis had high heterossis than eighth and seventh internode.2. The dynamic expression patterns of mi RNAs at the eighth internode under eat in the hybrid Xundan20 and its corresponding parents was identified through deep-sequence method.We found that the abundance of mi RNA was difference in the materials, more than 10,000,000 copys of mi RNA168 in the inbred line Xun9058, but only 1 copy mi RNA393 b.This result showed that the expression level of different mi RNA was diversity. Additionally, not all the members of the same mi RNA family were detected and the abundance of different member was different. The overwhelming majority expression pattern was over low parent, and the second expression pattern was over high parent. These results implied that over parent expression patterns of different mi RNA might play an important role in the elongating internode heterosis under ear at the mi RNA regulation level. With software ps RNATarget analysis, 99 conserved mi RNA and a total of 246 mi RNA target genes were found in this study. Most of these target genes were classified as transcriptional regulators(101/246), followed by signal transduction factors(28/246) and developmental factors(27/246). Eight new mi RNAs were discovered, most of its target genes were post-transcriptional regulators(7 / 52), and stress response factors(7/ 52). Detecting target genes’ expression profile, we found that many genes showed the opposite trend of expression level to mi RNAs. However the mi RNA, Tn1, T169 a and T172a-d, had not fount a clearly opposite expression profile. These results may suggest that besides the corresponding mi RNAs, the expression of these genes may influenced by other factors.3. With the analysis of protein profile, most of protein expression patterns were found close to their mid-parent, this result suggested that the gene mid-parent expression pattern might be important to the formation of ear height heterosis. We also found that some spots expression pattern were unique. For example, the protein expression in hybrids was 0 and the expression level in their parents was high, which also suggested that the gene expression and regulation were diversity, the regulation of gene expression might be closely related to heterosis formation. There were 66 protein spots were identified by ESI / MS / MS. Through GO annotation, most proteins(49/66) participated metabolism, 5 proteins related to the genetic information processing. Different expression proteins involved in diversity metabolic pathways, including pyruvate metabolism, pentose phosphate pathway, amino acid biosynthesis, synthesis of secondary metabolites, protein metabolism, RNA degradation and other metabolic pathways. We detected seven proteins had more than one point, indicated that post-translational modifications might play a role in the heterosis formation.In summary, the genetic bases heterosis is complex. One possible model of heterosis is that the interaction between alleles reduces the expression level of mi RNA, promoting the synthesis of transcription factors, thereby promoting the expression of functional genes in appropriate level. Then the cell metabolism can process at high efficiency, and finally showed heterosis.