| Heterosis was defined as the advantage of hybrid performance over its parents in terms of growth and productivity. Previous studies showed that differential gene expression between hybrids and their parents is responsible for the heterosis; however, information on systematic identification and characterization of the differentially expressed genes are limited.1. In this study, an interspecific hybrid between common wheat (Triticum. aestivum. L, 2n=6x=42, AABBDD) line 3338 and spelt {Triticum. spelta L. 2n=6x=42, AABBDD) line 2463 was found to be highly heterotic in both aerial growth and root related traits, ten root characters were measured including total root length (TRL), root surface area (RSA), root average diameter (RAD), root tips number (RTN), longest root length (LRL), taproot number (TN), taproot length (TL), root volume (RV), root dry weight (RDW) and root/shoot ratio (RSR). We observed significant MPH (P<0.05) for five traits (TRL, RSA, RV, RTN and RDW).2. Suppression subtractive hybridization was performed to generate four subtracted cDNA libraries, designated FSL (forward subtractive library of leaves), RSL (reverse subtractive library of leaves), FSR (forward subtractive library of roots), and RSR (reverse subtractive library of roots), which enriched gene expressed specifically or at higher level in hybrid leaves, parent leaves, hybrid roots and parent roots, respectively. A total of 748 nonreduandant cDNAs were obtained, among which 465 had high sequence similarity to the GenBank entries and represent diverse functional categories, such as metabolism, cell growth and maintenance, signal transduction, photosynthesis, response to stress, transcription regulation and others.3. To further test the reliability of SSH and compare the expression pattern of differentially expressed cDNAs between hybrid and its parents, reverse northern blot analysis was conduced for a subset of 443 nonredunant cDNAs obtained from the root libraries. The results indicated that the expression patterns of 68.2% SSH-derived cDNAs were confirmed by reverse northern blot. We also performed the semi-quantitative RT-PCR analysis of 18 ESTs, which exhibited the similar results (72.2%). The differential expression patterns of another 3 ESTs were confirmed by real-time quantitative PCR.4. A total of 313 cDNAs were located on the Chinese Spring deletion map by in silico mapping with E-value thresholds e-30, and 104 cDNAs were mapped in rice heterotic loci regions by comparative mapping, in which 30 cDNAs for grains per panicle, 9 for tillers per plant, 34 for weight of 1000 grains and the 52 for yield.5. In silico cloning approach was applied to obtain full-length cDNA sequences from novel gene sequences and the sequences were confirmed by RT-PCR. We obtained 25 cDNAs containing complete open reading frames (ORF) according to bioinformatic analysis, which include fifteen putative wheat ribosomal protein genes (TaRP), small GTP-binding protein (TaRab), 20sproteasome β4, β5, β7 subunit (Ta20B4, Ta20B5, Ta20B7), ubiquitin-conjugating enzyme (TaUBC), inositol phosphatase-like protein (TaIPP), leucine-rich repeat protein (TaLRRP), ADP-ribosylation factor (TaARF), histone deacetylase (TaHD), and 14-3-3 protein (Ta14-3-3). And the spatio-temporal expression pattern and differential expression between hybrid and its parents were also determined by semi-quantitative RT-PCR.6. Three genes, such as Ta14-3-3 that was down-regulated in hybrid in leaf and root at tillering stage, TaARF and TaHD, both of which were up-regulated in hybrid, were overexpressed in Arabidopsis. The presence and the expression of Ta14-3-3, TaARF and TaHD in the transgenic Arabidopsis were confirmed in the transgenic plants. We found that the root length of transgenic plants of Ta14-3-3 was decreased by 22.7% in average as compared to that of wild type, and the leaf size and plant height was found to be increased in the transgenic plants of TaARF. In addition, the phenotypic abnormalities in leaf development such as asymmetric leaves were found in transgenic plan...
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