Arabidopsis CHROMOSOME TRANSMISSION FIDELITY 7 (AtCTF7/ECO1) is required for DNA repair, mitosis and meiosis.
Bottom Line: No significant change was observed in the expression of genes that influence entry into the endocycle.Analysis of meiocytes identified changes in chromosome morphology and defective segregation; the abundance of chromosomal-bound cohesion subunits was also reduced.Taken together our results demonstrate that Arabidopsis CTF7/ECO1 plays important roles in the preservation of genome integrity and meiosis.
Affiliation: Institute of Plant and Microbial Biology, Academia Sinica, Taipei, 11529, Taiwan.Show MeSH
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Mentions: Based on observations in other systems (Baudrimont et al., 2011; Rudra and Skibbens, 2012), we expected that inactivation of CTF7 should block the establishment of sister chromatid cohesion and result in meiotic defects. In order to investigate this possibility we analyzed meiotic chromosome spreads in ctf7-1 plants. Alterations were observed from the earliest stages examined, with the first noticeable difference between ctf7-1 and WT plants being the presence of fewer meiocytes overall throughout meiosis. It is not clear if this is due to the fact that the plants are smaller and less healthy, or if some ctf7-1 microsporocytes arrest and abort prior to meiosis. Some variability was also observed in the phenotypes at different stages of meiosis, with some meiocytes appearing relatively normal; however, most meiocytes shared common phenotypes, which are described below. During pre-leptotene, WT chromosomes showed faint labeling of chromosomes with chromocenters that stain deeply (Ross et al., 1997; Figure S3a for WT), while in ctf7-1 plants no chromosome axes were recognizable and the chromocenters stained very faintly (Figure 3a). Similar to WT, chromosome condensation was observed during leptotene in ctf7-1, although at somewhat reduced levels (Figures 3b and S3b for WT). During zygotene, chromosome alignment was reduced in ctf7-1 (Figures 3c and S3c for WT) and ultimately a mixture of unpaired and unevenly paired chromosomes were observed at pachytene (Figures 3d S3d for WT). During diplotene, a decondensed mass of chromatin was typically observed in ctf7-1; no individual separated chromosomes were visible (Figures 3e and S3e for WT). In contrast to the five bivalents observed in WT at diakinesis (Mercier et al., 2005; Figure S3f for WT) a mixture of uncondensed chromatin, unpaired chromosomes and possibly some bivalents were observed in ctf7-1 (Figure 3f). Beginning at diplotene and diakinesis and continuing through meiosis II, ctf7-1 meiocytes typically appeared less condensed than their WT counterparts. A relatively small number of cells (10%) also appeared to contain extra chromosomes (Figures 3e–g and S3e–g for WT), although it is not clear whether this was caused by defects in chromosome segregation or DNA replication.
Affiliation: Institute of Plant and Microbial Biology, Academia Sinica, Taipei, 11529, Taiwan.