Abstract：Influence of epigenetic variation on phenotypic diversity has become a research hotspot recently. However, it remains largely unknown how epigenetic variation regulates plant phenotypic diversity. In this research, the leaf length diversity of 27 Arabidopsis thaliana genotypes and its correlation with DNA methylation of related genes to leaf development were studied. The results showed that a great leaf length diversity existed among different A. thaliana genotypes. After treatment with demethylation agent 5-azacytidine (5-azaC), leaf length variation of different genotypes decreased significantly. The leaf length of long-leaved A. thaliana genotypes decreased after 5-azaC treatment while short-leaved populations tend to increase. Leaf development related genes of different A. thaliana genotypes showed various DNA methylation levels via bioinformatics analysis. Meanwhile, leaf length of different A. thaliana genotypes were positively and significantly correlated with DNA methylation of 4 genes struwwelpeter (SWP), auxin response factor 2(ARF2), growth-regulating factor 1(GRF1), erbb-3 epidermal growth factor receptor binding proteinebp1(EBP1)which involved in A. thaliana leaf development. Three typical A. thaliana genotypes with different leaf lengths, long-leaved Gr-1, mediate leaved Ty-0 and short-leaved Br-0, were selected and used for gene expression analysis. The results showed that long-leaved Gr-1 had highest methylation levels of SWP, ARF2, GRF1 and EBP1 genes among the three selected populations while short-leaved Br-0 had lowest methylation levels of SWP, ARF2 and GRF1 and mediate methylated EBP1 gene. Q-PCR analysis showed that expression levels of these 4 genes were positively correlated with DNA methylation level and leaf length of A. thaliana genotypes, respectively. Gr-1 had the highest expression levels of SWP, ARF2, GRF1 and EBP1 genes compared with the other two populations. Br-0 had the lowest expression of SWP, ARF2 and GRF1 genes and the mediate expression level of EBP1 gene. However, relative expression level differences of these 4 genes among the 3 genotypes decreased significantly after 5-azaC treatment. The relative expression levels of SWP, ARF2, GRF1 and EBP1 in Gr-1 decreased significantly after 5-azaC treatment while relative expression levels of those four genes in Br-0 increased. In conclusion, demethylation of these 4 genes led to smaller relative expression level differences among the 3 populations, which contributed to the less leaf length diversity. These results indicated that DNA methylation of SWP, ARF2, GRF1 and EBP1 genes play a role in regulating leaf length diversity of A. thaliana. This may provide a basis for further study of the role of epigenetic variation on plants phenotypic diversity.
