Different Expression Of A Few Gene Families In Different Ploidy Rice And The Preliminary Research On DNA Methylation Regulation

Polyploidy plays an important role in the plant evolution, all Gramineae experienced one or more polyploidization beforedivergence. Polyploidy can cause some or all genome repeat, mRNA expression will be impacted inevitably by this repeat, then the corresponding protein expression will be impacted, finally the function and characters of the whole plant will be impacted. We used haploid, diploid and triploid rice derived from the same twin-seedling as our research materials in this study, According to gene chip analysis, we found many gene families was expressed differently in different ploidy rice. Was gene expression regulation related to the function of gene, developmental stages and organs in different ploidy rice? To investigate this question, we chose three important gene families which mRNA expression changed in different ploidy rices, that are SNF2gene family (Involved in transcriptional activation), ethylene synthesis related sites(involved in ethylene synthesis, and ethylene is related to plant senescence and fruit ripening) and recombinant DNA repair-related sites(involved in genome stability and tumor formation), totally10genes as our research object, we use quantitative PCR method, MeDIP-SEQ data and bisulfite sequencing method to make sure the expression variation in different ploidy rice, different developmental stages and different organs, analysis DNA methylation regulation manner of gene expression, and ploidy regulationof gene expressioncharacteristics and patterns in different ploidy rice. The main research results as follows:1. Results of quantitative PCR:(1) Genes has different function which expression is different in the different ploidy, different developmental stages of different organs, but they also have some common traits:①SNF2gene family:gene expression increased following with increased ploidy in the seedling stage of leaves and stems; gene expression was the lowest in the diploid of the stage that pulvinus distance is zero and booting stage of the leaves; but gene expression(except for SNF2-3((LOC_Os07g46590.1)) was the highest in the diploid of the heading stage of the panicles and stems, the expression increased following ploidy in the panicles; SNF2gene family was not expressed in the seedling stage of the roots.②Ethylene synthesis related sites gene family:gene expression increased following with ploidy in the seedling stage of stems, booting stage of stems and heading stage of panicles; gene ethylene-1(LOC_Os07g48630) expression increased following with ploidy, the other three genes expression change trend was consistent, that was the lowest in the diploid; gene expression was the highest in the diploid of the seedling stage and heading stage of the leaves.③Recombinant DNA repair-related gene DNA-3(LOC_Os02g26614):The gene was not expressed in the seedling stage of the roots and heading stage of the leaves and panicles; Gene expression was different in different ploidy of different developmental stages, it expresson was the highest in the haploid of the seedling stage of the leaves and stems, and it expression was the highest in the diploid of the booting stage of the leaves and stems.(2) Different gene expression of the same gene family was different in the different ploidy. For example, in the heanding stage of leaves, Ethylene synthesis related sites of gene ethylene-1(LOC_Os07g48630)which expression was:3N>N>2N, gene ethylene-2(LOC_Os03g20780.1) expression was:2N=3N>N, both ethylene-3(LOC_Os03g20790) and ethylene-4(LOC_Os03g20790.1) were:2N>N>3N.(3) Gene expression has organ-specific in different ploidy rices.①SNF2and ethylene synthesis related sites gene families, except for ethylene-3, the other eight genes were not expressed in the haploid.②In the heading stage of leaves, stems and panicles, DNA-3(LOC_Os02g26614)was only expressed in the stems, and it was not expressed in the leaves and panicles.2. Bisulfite sequencing resultsWe chose the gene LOC_Os07g31450.1which relation is negative correlation between methylation and gene expression, then tested the methylation status which is in different ploidy rice.In this study, we chose the promoter region of this gene to test its methylation modification of cytosine by bisulfite sequencing, in haploid we found that the methylation modification of cytosine in the promoter region is71, in diploid is77, in triploid is73. The results showed that DNA methylation existed differences in different ploidy rice, the chang trend was:1N<2N>3N.The change trend of corresponding gene expression is:1N>2N<3N, the changes between DNA methylation and gene expression were opposite, it showed that the methylation in the promoter region can inhibit gene expression. We conclude that the gene LOC_Os07g31450.1expression is different in different ploidy rice, and related to methylation degree.In conclusion, ploidy can regulate gene expression, some genes expression carry developmental stage and organ specificity, In addition, gene expression is different if gene has different function under the ploidy regulation. And DNA methylation can also participate in gene expression regulation.