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Reprogramming of rye rDNA in triticale during microsporogenesis
1Departamento de Botânica e Engenharia Biológica, Instituto Superior de Agronomia, Lisboa, Portugal.
Summary
Meiotic reprogramming activates silenced rye ribosomal DNA in triticale pollen. This epigenetic reset, involving methylation patterns, allows all nucleolar organizing regions (NORs) to function in young pollen grains.
Area of Science:
- Genetics
- Epigenetics
- Plant Biology
Background:
- Nucleolar dominance, a phenomenon where certain ribosomal RNA gene loci are preferentially expressed, is crucial in interspecific hybrids.
- Understanding the epigenetic mechanisms governing nucleolar dominance is key to plant breeding and development.
Purpose of the Study:
- To investigate if interspecific genomic interactions causing nucleolar dominance can be reprogrammed during meiosis in hexaploid triticale.
- To compare the activity of different nucleolar organizing region (NOR) loci across various developmental stages.
Main Methods:
- Silver staining of interphase and metaphase cells to quantify nucleoli and active NOR loci.
- Comparative analysis of ribosomal RNA (rRNA) gene activity in somatic cells, pollen mother cells, and young pollen grains.
Main Results:
- Somatic and pollen mother cells showed preferential activity of wheat NORs (1B, 6B) over rye NORs (1R).
- In young pollen grains, all NORs, including rye 1R NORs, were consistently active post-meiosis.
- Differential rRNA gene expression suggests a meiotic reprogramming of rye-origin rDNA.
Conclusions:
- Meiosis triggers a reprogramming of rye-origin ribosomal DNA (rDNA) in triticale.
- Epigenetic modifications, specifically resetting of methylation patterns, are likely responsible for the differential NOR expression observed during triticale development.