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Research Progress

DNA Methylation Interaction Mediated by RdDM Not Involved in Hybrid Vigor

Jul 06, 2016

Hybrid vigor, or heterosis, is paramount trait for plant growth and crop breeding. The molecular mechanism is unclear for a long term though several models were proposed. Arabidopsis, a model plant, is suitable for detection of heterosis mechanism, in which the F1 hybrids by crossing different accessions exhibit clear growth hybrid vigor in the early development stages.

Previously, RNA directed DNA methylation (RdDM pathway) is proposed to be responsible for the higher DNA methylation levels and 24nt siRNA profiles of F1 hybrids compared to parents, and thereby involved in regulation of hybrid vigor. But this hypothesis lacks concrete evidence.

Prof. ZHU Jiankang’s lab at the Shanghai Center for Plant Stress Biology (PSC), Shanghai Institutes for Biological Sciences of Chinese Academy of Sciences developed a new epigenomic algorithm identifying more than 3000 methylation interaction loci including not only hundreds of loci locating in the differentially methylated regions (DMRs) between parents as previously reported, but more than 2000 loci derived from similarly methylated regions (SMRs) newly identified in the study.

After NRPD1 and NRPE1, the key factors of RdDM pathway, are mutated, the DNA methylation interaction was lost, which indicates that RdDM regulates the DNA methylation interactions in Arabidopsis. Unexpectedly, hybrid vigor was still maintained after dysfunction of NRPD1 and NRPE1. Thus, RdDM is not involved in regulation of hybrid vigor though it is critical for maintenance of DNA methylation interaction in hybridization.

The findings further demonstrated that DNA methylation is not an important epigenetic factor for regulation of hybrid vigor.

This work was published online in PNAS entitled “Methylation interactions in Arabidopsis hybrids require RNA-directed DNA methylation and are influenced by genetic variation."

The study was supported by the Chinese Academy of Sciences and the National Institutes of Health, USA.

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