Primary Studies On The Nucleocytoplasmic Interaction In Tetraploid Rice

Rice is one of the most important food crops,feeding about one-third of the world’s population.Mitochondria and chloroplasts are very important organelles in eukaryotic cells,which are involved in many life activities.Chloroplasts and mitochondria are subcellular organelles with their own genomes and genetic systems.In the course of evolution,the mitochondria,chloroplasts and the nucleus have undergone precise mutual regulation and coevolution process to maintain the intracellular equilibrium state.Genome polyploidy,also known as a Whole Genome Duplication or Polyploid,can result in increased chromosomal duplication resulting in the creation of a large number of multi-copy genes.According to their formation mechanism,polyploid species can be divided into allopolyploid(species formed by hybridization of different species)and autologous polyploid(polyploid species formed by doubling of a single species).At the early stage of tetraploid formation,it is necessary to overcome the incongruent phenomena caused by whole-genome doubling,which makes synthetic tetraploid an ideal material for studying the mechanism of cytoplasmic interaction.In this study,we selected HJK and 9311 as the diploid parents and formed two control groups with the synthetic tetraploid HJK 4× and 9311 4×.We conducted a preliminary investigation on the nucleoplasmic interaction mechanism of rice tetraploid.The main results are as follows:1.By measuring the plant,leaf,stem,grain and other indexes of the two groups,it can be found that the leaf area,chlorophyll content,stomatal size,stem diameter,grain size,1000-grain weight and other aspects of tetraploid are significantly increased compared with diploid in the mature stage.These results indicated that the whole genome doubling event had an effect on plant morphology,photosynthesis,and grain characteristics.2.In the seedling stage leaf mesophyll cells of transmission electron microscope,we found that the tetraploid controls the chloroplast in mesophyll cells with the diploid number compared with the average increase 2-3,this shows that the whole genome doubling,chloroplast number of leaves increase,we suspect that this is one of the reasons for the cause of leaf chlorophyll content.3.By sequencing the organelle genomes of diploid and tetraploid,we found that the mitochondrial genome size of tetraploid was significantly different from that of diploid,and the range of change in both groups was about 60 kb.Moreover,the mitochondrial genome structure changed greatly.Through the analysis of the genome structure of the two control groups,we learned that after the doubling of the whole family genome,a large number of rearrangement events occurred in the mitochondrial genome,which was the main reason for the changes in the genome structure.However,in the analysis of the chloroplast genome structure of the two control groups,we found that the variation range of chloroplast genome size was significantly lower than that of mitochondria.The genome structure was not only relatively conserved after doubling,but also basically conserved in different control groups,and only 1-2 rearrangement events were observed after the whole genome doubling.This shows that the chloroplast genome structure is stable and conserved.4.Through the l nuclear gene transcriptome analysis of two groups,we found that the tetraploid relative diploid nuclear gene expression changes significantly,the enrichment of major changes in the synthesis and metabolism of lipids to secondary metabolic pathways,suggesting that whole genome doubling for affected the secondary metabolism and lipid levels.Through transcriptome analysis of organelle genomes,we found that the expression levels of both mitochondrial and chloroplast genes did not change significantly,and the variation range of mitochondrial gene expression was-0.4-0.6 times.The expression level in chloroplasts varied from-0.5 to1.5 times.This indicates an imbalance of gene expression levels in the nucleus and cytoplasm after genome-wide doubling.5.Through the prediction of the subcellular localization of common differential genes,mitochondrial and chloroplast localized genes were screened and GO enrichment analysis was performed on them.Through the analysis and verification of the enrichment results,it was found that genome-wide doubling events significantly affected the organelle OXPHOS pathway.At the same time,through the analysis and verification of the proteins of the nuclear coding organelle complex,it was found that the expression levels of the co-altered genes involved in the synthesis of the OXPHOS complex were up-regulated in both groups,indicating that the whole genome doubling event was involved in the regulation of the OXPHOS capacity of the plant body and changed the energy metabolism of the plant.