Alteration Of Gene Expression In Early Developing Stages Of Cross-pollinated And Self-pollinated Seeds And Heterosis In Wheat

In order to further understand molecular basis of heterosis, mRNA differential display reverse transcription PCR (DDRT-PCR) and cDNA amplified fragment length polymorphism (cDNA-AFLP) were used to analyze the alterations in gene expression between seeds of 1 8 reciprocal hybrids and their 6 parents at 6th day and 12th day after pollination (6DAP and 12DAP). The relationship between gene expression patterns and heterosis was determined and some differentially expressed genes were cloned and sequenced. The results were as follows:1 . The patterns of gene expression at 6DAP were same as those of 12DAP, which were classified as eight patterns (in total fifteen kinds). The results indicated that differences of gene expression between hybrids and their parents were obvious , whose percentage changed in the range of 40-60%. The number of amplified gene fragments at 12DAP reduced by 28% as compared to that of 6DAP. The percentage of differentially expressed genes by about 1 1 .72%.2. Heterosis observed in number of effective tiller , grain number per ear and grain yield per plant were significantly negatively correlated with the tOlll expression pattern.. Heterosis observed in thousand grain weight were significantly negatively correlated with tOOlO expression pattern. Heterosis observed in ear length were significantly negatively correlated with the tlOOO expression pattern. And heterosis observed in number of effective tiller were significantly positively correlated with the tlOOl expression pattern at 6DAP. The tOOll and tOUO expression pattern significantly positively correlated with number of effective tiller , grain number per ear and grain yield per paint. The tOOll expression pattern also significantly correlated with grain yield per ear. tlOOl expression pattern significantly negatively correlated with biomass per plant at 12DAP.3. Eighty-nine differentially expressed cDNA fragments were cloned. Compared to sequences in GenBank, it was found that there were about fifty-five genes involved in metabolic pathways including carbohydrate metabolism (six genes), fatty acid metabolism (three genes), protein synthesis (nine genes), protein catabolism (three genes), amino acid metabolism (two genes), nucleic acid metabolism (four genes), nucleotide metabolism (two genes), regulatory protein (six genes), transmembrane transport (five genes), energy conversion (four genes), signal transduction (two genes), storage protein (ten genes) and other pathways (one gene). There were additional thirty-four cDNA fragments whose functions were unknown. The exprssion pattern of twenty-five genes were significantly correlated with agronomic trait heterosis according to the relationship between patterns of gene expression and heterosis.