表观遗传修饰新发现

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4. Result
4.2 The sldml2 mutations inhibit fruit ripening.
郝雪峰
2017.10.18
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DNA methylation is a conserved epigenetic mark important for genome integrity, development, and environmental responses in plants and mammals.
➢DNA methylation is generally associated with inactive transcription .
➢Active DNA demethylation is critical for gene activation or for the prevention of silencing.
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In contrast to Arabidopsis, Tomato is an economically important crop and a model for studying fleshy fruit ripening .
Fruit ripening is associated with many distinct changes, which are driven by phytohormones and developmental factors.
Active DNA demethylaton in plants is initiated by a family of 5-mC DNA glycosylases/lyases( i.e., DNA demethylases).
This study suggests that active DNA demethylation is required for both the activation of ripening-induced genes and the inhibition of ripening-repressed genes.
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2.1 Research Background
Cytosine methylation levels & gene activation
➢5-mC levels are dynamically regulated by methylation and demethylation reactions.
➢ compared the DNA methylomes of WT and sidml2 mutant fruits;
Analyzed the transcriptome of sidml2 mutant fruits.
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4. Result
4.1 Generation of stable loss-of-function mutant alleles of SlDML2 using the CRISPR/Cas9 gene-editing system.
➢SlDML 1～4 ➢SlDML 1/2：most closely related to AtROS1
SlDMLs play critical roles in fruit ripening.
➢RNAi against the conserved HhH-GPD domain
Which SlDML(s) is required for fruit ripening? What impact dose active DNA demethylation have on the genome-wide during fruit ripening?
DNA methylation பைடு நூலகம்ite:
➢In mammals : CG （DNMTs）
➢In plants : CG （ MET1 ） /CHH （ CMT2, DRM2 ） /CNG （CMT3）
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2.2 Research Background
•ROS1 preferentially targets TEs
PNAS Published online May 15, 2017
Critical roles of DNA dmethylation in the activation of ripening-induced genes and inhibition
of ripening-repressed genes in tomoto fruit
In addition to ethylene and the TFs, DNA methylation is another key regulator of fruit ripening.
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2.4 Research Background
Tomato contains four putative DNA demethylases:
➢TEs （Transposable Elements） ➢When ROS1 targeted TEs are located in the promoter regions of genes, ROS1 can protect gene expression by demethylating the adjacent TEs. ➢Many studies have demonstrated that, by demethylating nearby TEs, active DNA demethylation is critical for gene activation or for the prevention of silencing .
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Generated two mutant alleles of SlDML2 .
➢ in the tomato cultivar Micro-Tom ➢ using CRISPR/Cas 9 system
Determined the genome-wide effect of SlDML2 on DNA demethylation.