Loss of function mutations in the rice chromomethylase OsCMT3a cause a burst of transposition. (September 2015)

• Record Type: Journal Article
• Authors: Cheng, Chaoyang; Tarutani, Yoshiaki; Miyao, Akio; Ito, Tasuku; Yamazaki, Muneo; Sakai, Hiroaki; Fukai, Eigo; Hirochika, Hirohiko
• Is Part Of: Plant journal. Volume 83:Number 6(2015:Sep.)
• Page Start: 1069
• Page End: 1081
• Publication Date: 2015-09
• Subjects: Plant molecular biology -- Periodicals; Plant cells and tissues -- Periodicals; Botany -- Periodicals; 580
• DOI: 10.1111/tpj.12952
• Languages: English
• ISSNs: 0960-7412

Abstract

<abstract abstract-type="main" id="tpj12952-abs-0001"> <title>Summary</title> <p>Methylation patterns of plants are unique as, in addition to the methylation at CG dinucleotides that occurs in mammals, methylation also occurs at non‐CG sites. Genes are methylated at CG sites, but transposable elements (TEs) are methylated at both CG and non‐CG sites. The role of non‐CG methylation in transcriptional silencing of TEs is being extensively studied at this time, but only very rare transpositions have been reported when non‐CG methylation machineries have been compromised. To understand the role of non‐CG methylation in TE suppression and in plant development, we characterized rice mutants with changes in the chromomethylase gene, <italic>OsCMT3a. oscmt3a</italic> mutants exhibited a dramatic decrease in CHG methylation, changes in the expression of some genes and TEs, and pleiotropic developmental abnormalities. Genome resequencing identified eight TE families mobilized in <italic>oscmt3a</italic> during normal propagation. These TEs included tissue culture‐activated copia retrotransposons <italic>Tos17</italic> and <italic>Tos19</italic> (<italic>Lullaby</italic>), a pericentromeric clustered high‐copy‐number non‐autonomous gypsy retrotransposon <italic>Dasheng</italic>, two copia retrotransposons <italic>Osr4</italic> and <italic>Osr13</italic>, a hAT‐tip100 transposon <italic>DaiZ</italic>, a MITE transposon <italic>mPing</italic>, and a LINE element <italic>LINE1‐6_OS</italic>. We confirmed the transposition of these TEs by polymerase chain reaction (PCR) and/or Southern blot analysis, and showed that transposition was dependent on the <italic>oscmt3a</italic> mutation. These results demonstrated that OsCMT3a‐mediated non‐CG DNA methylation plays a critical role in development and in the suppression of a wide spectrum of TEs. These <italic>in planta</italic> mobile TEs are important for studying the interaction between TEs and the host genome, and for rice functional genomics.</p> </abstract>