期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2022
卷号：119
期号：13
DOI：10.1073/pnas.2112240119
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Significance
Paramutation involves the transfer of a repressive epigenetic mark between silent and active alleles. It is best known from exceptional non-Mendelian inheritance of conspicuous phenotypes in maize but also in other plants and animals. Recent genomic studies, however, indicate that paramutation may be less exceptional. It may be a consequence of wide-cross hybridization and may contribute to quantitative trait variation or unstable phenotypes in crops. Using the
sulfurea (
sulf) locus in tomato, we demonstrate that a self-reinforcing feedback loop involving DNA- and histone-methyl transferases CHROMOMETHYLTRANSFERASE3 (CMT3) and KRYPTONITE (KYP) is required for paramutation of
sulf and that there is a change in chromatin organization. These findings advance the understanding of non-Mendelian inheritance in plants.
Paramutation involves the transfer of a repressive epigenetic mark from a silent allele to an active homolog and, consequently, non-Mendelian inheritance. In tomato, the
sulfurea (
sulf) paramutation is associated with a high level of CHG hypermethylation in a region overlapping with the transcription start site (TSS) of the
SlTAB2 gene that affects chlorophyll synthesis. The CCG subcontext hypermethylation is under-represented at this region relative to CTG or CAG, implicating the CHROMOMETHYLTRANSFERASE3a (CMT3) in paramutation at this locus. Consistent with this interpretation, loss of
CMT3 function leads to loss of the
sulf chlorosis, the associated CHG hypermethylation, and paramutation. Loss of
KRYPTONITE (KYP) histone methyltransferase function has a similar effect linked to reduced H3K9me2 at the promoter region of
SlTAB2 and a shift in higher order chromatin structure at this locus. Mutation of the largest subunit of RNA polymerase V (
PolV) in contrast does not affect
sulf paramutation. These findings indicate the involvement of a CMT3/KYP–dependent feedback loop rather than the PolV-dependent pathway leading to RNA-directed DNA methylation (RdDM) in the maintenance of paramutation.
