| It becomes one of important research directions on crop genetics and breeding to investigate crop heterosis through gene expression when biology enters a era of functional genomics. The cDNAchip as a new molecular technique has provided a powerful tool to study heterosis under the gene expression level. The purpose of this study is to get the gene expression profile of the hybrid and its parents using cDNA chips in order to explore the molecular basis of heterosis.In this study, an elite maize hybrid (Yuyu22) and its parents (Zong3, 87-1) were used as materials. Heterosis of their roots in seedling was evaluated with WinRHIZO, an optical-scanner-based image analysis system. The gene expression profile in maize roots was investigated using a rice cDNA chip, where there were 9196 rice unigenes. The gene expression patterns were also analyzed. The functions of differential expressing genes between the hybrid and its parents were predicted by Blastx research and other bioinformatics means. A special differential expressing gene was confirmed by RT-PCR, following the sequence analysis. Some useful results can be drew out as follows:1. After eight days of germination under the water culture, there was significant heterosis in several root's morphology characteristics, including total lengths, surface areas, root volumes and numbers of lateral roots. Their over-parent heterotic values were 55.9%, 63.6%, 80% and 493%, respectively. Dry weight of root also exhibited the same over-parent heterosis, with a value of 58.3%. It suggested that roots may be used as a model characteristic to study crop heterosis.2. Based on data from the chip hybridizations, there were only 137 genes expressed differentially between hybrid and its parents among 7954 dots of valid hybridization, reached to 1.49% of total dots. It suggested that the number of genes showing differential expression was limited. Among differential expressing genes, 30 genes were up-regulated while 107 down-regulated, being 21.9% and 78.1% of total, respectively.3. Among five types of gene expression patterns ( I, up-regulated in hybrid to both parents; II, down-regulated in hybrid to both parents; III. expresses in hybrid between the level of two parents; IV. expresses in hybrid as a lower parent; V. expresses in hybrid as a higher parent), the most gene expression patterns were type IV, reached to 70.6 %, type II accounted for 7.4%. However, the other three types only made up 22% altogether. A conclusion may be drew that the repression of some genes' expression may play a certain role in the root heterosis. Additionally, Five fold difference of gene expression between F1 and its parents were detected.4. According to a BLASTX search in GenBank, these differential expression genes may encode different functional proteins, including structure protein, enzyme, transporter, transcription factor, signal transducer and so on. 12 genes were involved in the replication, transcription and post-transcription mechanism of nucleotide, accounted for 8.8% of total differential expression genes; 11 may be related to transporter, being 8.1%; Some other genes involved in synthesis of organic compound, signal transduction, cell division and elongation, photosynthesis and resistance to stress. These genes numbers and it's proportion were 11, 8.1%; 4, 2.9%; 4,2.9%; 20,14.6%; 10,7.3% respectively. The functions of 48 genes (35.0%) were unknown and 11 genes (8.1%) were no homology to any known genes among differential expressing genes. Additionally, one gene that was similar to germin was confirmed by RT-PCR analysis.
|
PDF Full Text Request