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Published on: August 24, 2013
A Hypomorphic Mutant of PHD Domain Protein Male Meiocytes Death 1
Bing Liu1,2, Chunlian Jin2, Nico De Storme2,3
1College of Life Sciences, South-Central University for Nationalities, Wuhan 430074, China.
Abstract:
Meiosis drives reciprocal genetic exchanges and produces gametes with halved chromosome number, which is important for the genetic diversity, plant viability, and ploidy consistency of flowering plants. Alterations in chromosome dynamics and/or cytokinesis during meiosis may lead to meiotic restitution and the formation of unreduced microspores. In this study, we isolated an Arabidopsis mutant male meiotic restitution 1 (mmr1), which produces a small subpopulation of diploid or polyploid pollen grains. Cytological analysis revealed that mmr1 produces dyads, triads, and monads indicative of male meiotic restitution. Both homologous chromosomes and sister chromatids in mmr1 are separated normally, but chromosome condensation at metaphase I is slightly affected. The mmr1 mutant displayed incomplete meiotic cytokinesis. Supportively, immunostaining of the microtubular cytoskeleton showed that the spindle organization at anaphase II and mini-phragmoplast formation at telophase II are aberrant. The causative mutation in mmr1 was mapped to chromosome 1 at the chromatin regulator Male Meiocyte Death 1 (MMD1/DUET) locus. mmr1 contains a C-to-T transition at the third exon of MMD1/DUET at the genomic position 2168 bp from the start codon, which causes an amino acid change G618D that locates in the conserved PHD-finger domain of histone binding proteins. The F1 progenies of mmr1 crossing with knockout mmd1/duet mutant exhibited same meiotic defects and similar meiotic restitution rate as mmr1. Taken together, we here report a hypomorphic mmd1/duet allele that typically shows defects in microtubule organization and cytokinesis.
Insights
A new Arabidopsis mutant, male meiotic restitution 1 (mmr1), exhibits defects in meiosis, producing unreduced pollen due to incomplete cytokinesis and aberrant microtubule organization. This study identifies a hypomorphic allele of Male Meiocyte Death 1 (MMD1/DUET) as the cause.
Area of Science:
- Plant genetics
- Molecular biology
- Cell biology
Background:
- Meiosis is crucial for plant reproduction, ensuring genetic diversity and ploidy stability.
- Aberrant meiotic processes, such as meiotic restitution, can lead to the formation of unreduced gametes.
Purpose of the Study:
- To investigate the genetic basis of male meiotic restitution in Arabidopsis.
- To characterize the cytological defects associated with meiotic restitution in the identified mutant.
Main Methods:
- Isolation and characterization of the Arabidopsis mutant male meiotic restitution 1 (mmr1).
- Cytological analysis, including chromosome behavior and microtubule cytoskeleton immunostaining.
- Genetic mapping and molecular identification of the causative mutation.
- Complementation analysis with existing mutants.
Main Results:
- The mmr1 mutant produces diploid/polyploid pollen grains, indicating male meiotic restitution.
- Cytological defects include incomplete meiotic cytokinesis, aberrant spindle organization at anaphase II, and abnormal mini-phragmoplast formation.
- The mutation was mapped to the Male Meiocyte Death 1 (MMD1/DUET) locus, specifically a C-to-T transition causing a G618D amino acid change in a histone binding protein.
- Complementation analysis confirmed that mmr1 is a hypomorphic allele of MMD1/DUET.
Conclusions:
- The study identifies a novel hypomorphic allele of MMD1/DUET responsible for male meiotic restitution in Arabidopsis.
- The findings highlight the role of MMD1/DUET in regulating microtubule organization and cytokinesis during male meiosis.
- This research provides insights into the mechanisms underlying meiotic fidelity and its impact on plant reproduction.
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