The rice Os05g0580500 was reported as Rad21/Rec8  in 2006, by researchers from China
- Os05g0580500 <=> OsRAD21-4, OsREC8, OsRad21-4, REC8
- Rad21/Rec8 is an important component and key regulator of cohesins. OsRAD21-4, a RAD21-like gene from rice Zhonghua 10 (Oryza sativa L. ssp.japonica), is a single-copy gene in the rice genome and essential for eﬃcient meiosis.
- OsRad21-4 is composed of 20 exons and 19 introns. It encodes a relatively hydrophilic protein and contains the entire Pfam04825 and Pfam04824 domains (spanning amino acids 1–115 and 554–608, respectively) (Figure 2A), of which Pfam04825 is highly conserved in all known members and Pfam04824 present in most of the Rad21/Rec8 family. The two domain regions are spaced by a long linker sequence (amino acids 116-553).
- This linker sequence contains a potential nuclear targeting motif at positions 272–279 (KRKKRRKD), 2 separase recognition sites at 411–421 (ADDIEKLRGNT) and 420–430 (NTSGEYGRDYD) and a PEST motif at 511– 534 (RLSDVGPTPDLLEEIEPTQTPYEK) (Figure 2A). These motifs are proposed to be implicated in function regulation in cohesion establishment and disassociation.
- The deﬁciency of OsRad21-4 at the mRNA and protein is correlated with pollen cell sterility phenotype.(Figure6) OsRad21-4 was essential to meiosis. (Figure7, Figure8) In addtion, OsRad21-4 is responsible for the pairing of some homologous chromosomes.(Figure9, Figure10)
- OsRad21-4 is present in the rice genome as a single-copy gene. The mRNA and protein of OsRad21-4 were expressed preferentially in young ﬂowers where the pollen mother cells (PMCs) were in pre-meiotic stages. As shown in Figure 3A, OsRad21-4 was expressed preferentially in ﬂowers, weakly in leaves and barely in buds and roots.
- Furthermore, OsRad21-4 was expressed dominantly just before the premeiotic stage of PMCs.(Figure 3C) This gene should function in premeiotic and meiotic PMCs, which is consistent with this notion that meiotic cohesion is established at the pre-meiotic S phase. (Figur 4)
- OsRad21-4 is a rice orthologue of yeast Rec8.(Figure2(C)) In rice, OsRad21-4 is required for homologous pairing and segregation. It might be responsible mainly for sister chromatid-arm cohesion and to a lesser extent or not at all for centromere cohesion.
- In addition, OsRad21-4 is required for chromosome condensation. Besides, Zhang et al suggest possible link between Rec8 proteins and chromosome fragmentation in higher eukaryotes. Furthermore, appearance of micronuclei and/or undetached dinuclei-containing spores and unequal cell division at anaphase I and II in the deﬁcient plants were similar to those reported in mutants of genes related to other early events of meiosis prophase I, suggesting possible interaction of early events of prophase I.
Labs working on this gene
1.Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Research Center of Molecular & Developmental Biology, Institute of Botany, Chinese academy of Sciences, Beijing 100093,China
2.Graduate School of the Chinese Academy of Sciences, Beijing 100049, China
3.Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Hongo, Tokyo 113-0033, Japan
4.PRESTO, Japan Science and Technology Corporation, Kawaguchi, Saitama 332-0012, Japan
5.Imperial Cancer Research Fund, 44 Lincoln's Inn Field, London WC2A 3PX, UK
6.Division of Natural Science, Osaka Kyoiku University, 4-698-1 Asahigaoka, Kashiwara, Osaka 582-8582, Japan
7.Faculty of Health Sciences for Welfare, Kansai University of Welfare Sciences, 3-11-1 Asahigaoka, Osaka 582-0026, Japan
- Zhang L, Tao J, Wang S, et al. The rice OsRad21-4, an orthologue of yeast Rec8 protein, is required for efficient meiosis[J]. Plant molecular biology, 2006, 60(4): 533-554.
- Zhang L R, Tao J Y, Wang T. Molecular characterization of OsRAD21‐1, a rice homologue of yeast RAD21 essential for mitotic chromosome cohesion*[J]. Journal of experimental botany, 2004, 55(399): 1149-1152.
- Nasmyth K. Disseminating the genome: joining, resolving, and separating sister chromatids during mitosis and meiosis[J]. Annual review of genetics, 2001, 35(1): 673-745.
- Watanabe Y, Yokobayashi S, Yamamoto M, et al. Pre-meiotic S phase is linked to reductional chromosome segregation and recombination[J]. Nature, 2001, 409(6818): 359-363.
- Ma H. Molecular genetic analyses of microsporogenesis and microgametogenesis in flowering plants[J]. Annu. Rev. Plant Biol., 2005, 56: 393-434.