Mechanism Research Of Neutral Lipids Accumulation In Embryonic Callus Of Polycomb Group Proteins Mutants In Arabidopsis

Polycomb group (PcG) proteins, mainly including two multi-protein complexes Polycomb Repressive Complex 1 and 2 (PRC1, PRC2), are crucial epigenetic regulators widely involved in plant growth and development. The mutants with the loss-of-PRC function lead to the germination of embryonic callus (EC) and accumulation of neutral lipids TAG. The study for the calculation of neutral lipids in EC of ringla ringlb and swn3 clf29 was performed with the strategy of cell biology, bioinformatics and molecular biology and so on. The results were showed as follows:1, Histochemical staining and confocal observation showed that neutral lipid accumulation and oil body can be detected in the EC of double mutant of ringla ringlb (PRC1) and swn3 clf29 (PRC2).2, Thin layer chromatography (TLC) analysis indicated that a lot of TAGs which take the great part of lipids were accumulated obviously in EC, so did FFA and DAG, compared with the wild-type. Therefore, it directed that EC from PRC mutants both has the characteristics of seeds and leaves.3, Gas chromatography analysis showed fatty acid composition of EC is similar to the seed of wild-type, except the fatty acid composition in the seeds of PRC mutant is mainly composed of oleic acid, different from the seeds of wild-type.4,Transcriptome chip analysis further showed that mostly of the 275 genes correlated with the synthesis and metabolism of fatty acid were overlapped with the up-regulated genes in the mutant of ringla ringlb and swn3 clf29 and also the genes can be methylated with H3K27 trimethylation (H3K27me3).5, According to the experiments of qPCR and ChIP, the up regulated genes with the decreased levels of H3K27me3 in EC mostly associated with fatty acid synthesis, including FUS3, OLEO4 and SESA1, responsible for TAG synthesis, sequestering of oil for the synthesis of oilbody and transporting oil to seeds’ storage, respectively.In conclusion, Our results indicate that PRCs are necessary for repressing the expression of the genes responsible for seed maturation at the vegetative stages. PRC accurately inhibits the expression levels of genes corresponding to seed development, aggregation oil for the synthesis of oil body, and the transporting of fatty acid, but it does not affect the common pathway of membrane phospholipids and fat storage. And the repression of these genes is closely correlated with the deposition of H3K27me3, a repressive epigenetic marker.