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Figure 8. Abnormal meiotic chromosome behavior in microsporocytes of OsRad21-4-deficient lines. Meiosis chromosome spreads were prepared from fixed anthers from the deficient lines (R1 and R5, data are shown only for R5). (A) leptonema; chromatins were compacted into a entangled mass. (B) zygonema; chromosomes showed defects in condensation, with most regions being highly condensed in agglomeration. (C) and (D) pachynema, chromosomes were highly condensed compared with those of the wild type and unsynapsed homologues, with detached regions distal to centromeres and chromosome fragments visible (arrows); (E) diplonema; homologues precociously segregated into univalents. (F) diakinesis; univalent (not marked), bivalents (concaved arrows) and chromosome fragments (arrows) are visible. (G) late diakinesis; homologues precociously segregated into 24 univalents. (H) late diakinesis; �50 stained bodies, reflecting severe chromosome fragmentation. (I) and (J) metaphase I; chromosomes (arrows) did not align on equator. (K) anaphase I; chromosome bridging was formed by lagging chromosomes linking two segregating groups of chromosomes (arrows). (L) anaphase I; chromosomes segregated randomly. (M) telophase I; chromosomes cannot be segregated into each pole (arrows). (N) dyad with lost chromosomes and unequal nuclei. (O) dyad with 1 cell having 2 unequal nuclei. (P) dyad with unequal nuclei and cytoplasm. (Q) metaphase II, 2 daughters lost synchronization to initiate transition of metaphase II to anaphase II. (R) tetrad stage; misorientation of spindles in 2 daughters resulted in cell division occurring in 1 daughter but not the other. (S) tetrad stage; 4 cells with unequal cytoplasm and chromosome complements. Bar in (A) = 20 lm for (A)–(S).