The Arabidopsis SYN3 cohesin protein is important for early meiotic events

Abstract

SUMMARY a-Kleisins are core components of meiotic and mitotic cohesin complexes. Arabidopsis contains four genes that encode a-kleisin proteins: SYN1, SYN2, SYN3 and SYN4. SYN1, a REC8 ortholog, is essential for meiosis, while SYN2 and SYN4 appear to be SCC1 orthologs and function in mitosis. SYN3 is essential for megagametogenesis and is enriched in the nucleolus of meiotic and mitotic cells. In this study the role of SYN3 during meiosis was investigated by characterization of plants that express SYN3-RNAi constructs from either meiotic DMC1, native SYN3, or inducible PX7 promoters. Reduction of SYN3 caused defects in homologous chromosome synapsis and synaptonemal complex (SC) formation during male and female meiosis. Consistent with this observation, relatively little signal for the SC component ZYP1 was detected on the chromosomes of SYN3-RNAi plants. ZYP1 transcript levels were relatively normal, but several transcripts for genes that encode proteins involved in meiotic recombination were altered, which suggested that a reduction in SYN3 may inhibit meiotic progression by alteration of meiotic gene expression.

The Opposing Actions of Arabidopsis CHROMOSOME TRANSMISSION FIDELITY7 and WINGS APART-LIKE1 and 2 Differ in Mitotic and Meiotic Cells

“…They facilitate long-distance DNA interactions (Dorsett and Merkenschlager, 2013) and have been shown to affect long-range interactions between binding sites of the transcriptional repressor CTCF in a number of genes in animal cells (Bonora et al, 2014). Consistent with this, alterations in cohesin protein levels can result in tissue-specific alterations in transcript levels for a number of genes in Arabidopsis (this study; Yuan et al, 2012;Bolaños-Villegas et al, 2013;Liu and Makaroff, 2015). For example, transgenic plants expressing a pro35S:AtCTF7ΔB construct and ctf7 plants contain elevated levels of transcripts for epigenetically regulated transposable elements, including MU1, COPIA 28, and solo LTR, and alterations in transcript levels of several small interfering RNA-associated genes (Bolaños-Villegas et al, 2013;Liu and Makaroff, 2015).…”

The Arabidopsis homolog of Scc4/MAU2 is essential for embryogenesis

“…8). Overexpression of cohesin proteins affects meiotic cell division in Arabidopsis (Yuan et al, 2012). Therefore, we established lines expressing kleisin subunits under the control of the ABI3 promoter, which has a relatively low and localized activity (Ng et al, 2004).…”

“…The Arabidopsis genome encodes four kleisin subunits (Fig. 1A): the meiosis-specific SYN1 (Cai et al, 2003) and SYN3, involved in gene expression of meiotic genes, but also expressed in somatic cells (Yuan et al, 2012;Jiang et al, 2007), and SYN2 and SYN4, which have been suggested to participate in mitotic cell division (da Costa-Nunes et al, 2006).…”

Meiotic Chromosome Structure and Function in Plants

“…However, further studies point to SYN3 acting as a significant player during female meiosis [Yuan et al, 2012]. In SYN3 RNAi plants, male gametogenesis is only slightly affected, with a marginal reduction in pollen viability [Yuan et al, 2012]. Yet, these plants have significantly reduced fertility, resulting from the abortion of megaspore mother cells [Yuan et al, 2012].…”

“…However, further studies point to SYN3 acting as a significant player during female meiosis [Yuan et al, 2012]. In SYN3 RNAi plants, male gametogenesis is only slightly affected, with a marginal reduction in pollen viability [Yuan et al, 2012].…”