Abstract
The PAIR2 gene is required for homologous chromosome synapsis at meiosis I in rice (Oryza sativa L.) and encodes a HORMA-domain protein that is homologous to Saccharomyces cerevisiae HOP1 and Arabidopsis ASY1. Immunocytological and electron microscopic analyses indicate that PAIR2 proteins associate with axial elements (AEs) at leptotene and zygotene, and is removed from the AEs of arm regions when homologous chromosomes have been synapsed. Immunocytology against a centromeric histone H3 variant revealed that PAIR2 remains at centromeres until diakinesis, by which time the homologous centromeres had already been synapsed. However, neither precocious segregation of sister chromatids nor kinetochore dysfunction is observed, and AEs are normally assembled in the mutant. In the pair2-null mutant, homologous chromosome synapsis is completely eliminated. This study provides the first description of AE-associated protein in monocot plants and indicates that PAIR2 plays an essential role in promoting homologous chromosome synapsis. However, PAIR2 does not play a role in AE formation, sister chromatid cohesion at centromeres or kinetochore assembly in meiosis I of rice.
Highlights
Meiosis is a crucial event for sexual reproduction of eukaryotes to form haploid spores and gametes
axial elements (AEs) are normally assembled in the mutant
This study provides the first description of AE-associated protein in monocot plants and indicates that PAIR2 plays an essential role in promoting homologous chromosome synapsis
Summary
Meiosis is a crucial event for sexual reproduction of eukaryotes to form haploid spores and gametes. Meiosis is characterized by a single round of pre-meiotic DNA duplication followed by two rounds of chromosome segregation. In this process, homologous chromosomes are aligned and synapsed to prepare for faithful division of each homologous chromosome (homolog) at meiosis I. The mechanism of searching for homology among meiotic chromosomes is still unknown, homolog pairing is made solid by an evolutionarily conserved, tripartite, proteinaceous structure called the synaptonemal complex (SC). During early prophase of meiosis I, each chromosome develops a longitudinal axial protein core, called the axial element (AE), to which the chromatin loops are attached (Dobson et al, 1994). The axial cores separate while remaining attached at a few points, called chiasmata, which are presumably the sites of crossovers (von Wettstein et al, 1984)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
