Arabidopsis Cell Division Cycle 20.1 Is Required for Normal Meiotic Spindle Assembly and Chromosome Segregation

Abstract

Cell division requires proper spindle assembly; a surveillance pathway, the spindle assembly checkpoint (SAC), monitors whether the spindle is normal and correctly attached to kinetochores. The SAC proteins regulate mitotic chromosome segregation by affecting CDC20 (Cell Division Cycle 20) function. However, it is unclear whether CDC20 regulates meiotic spindle assembly and proper homolog segregation. Here, we show that the Arabidopsis thaliana CDC20.1 gene is indispensable for meiosis and male fertility. We demonstrate that cdc20.1 meiotic chromosomes align asynchronously and segregate unequally and the metaphase I spindle has aberrant morphology. Comparison of the distribution of meiotic stages at different time points between the wild type and cdc20

P31 comet , a member of the synaptonemal complex, participates in meiotic DSB formation in rice

“…In rice brk1-1 meiocytes, the spindle length was slightly elongated (38). In Arabidopsis cdc20.1, meiocytes exhibited atypical spindle morphology and had a longer average spindle length at metaphase I (37). Although p31 comet acts to monitor the spindle checkpoint in humans, we didn't found any defects in meiotic spindle assembly in the rice p31 comet mutant.…”

“…In addition, TRIP13 and p31 comet promoted the inactivation of the mitotic checkpoint (30). However, the function of SAC-related proteins in mitosis has not yet been tested in plants, and several SAC proteins have been found to be involved in plant meiosis, such as MPS1, Aurora kinases, AtPCH2, and CDC20.1 in Arabidopsis, as well as CRC1 and BRK1 in rice (12,37). In rice brk1-1 meiocytes, the spindle length was slightly elongated (38).…”

“…Highly conserved among eukaryotes, SAC proteins regulate chromosome segregation by sequestering CDC20 and promote the transition from metaphase to anaphase (36). Previous findings also reported that, in rice SAC protein Bub1-related kinase 1 (brk1) and Arabidopsis cell division cycle 20.1 (cdc20.1) mutants, the spindle lengths were a little bit longer than in the WT at metaphase I (37,38). Because p31 comet acts as an interacting partner of SAC effector molecule Mad2 in human (29), we thus investigated whether the loss of P31 comet is associated with the aberrant spindle assembly.…”

The Arabidopsis anaphase‐promoting complex/cyclosome subunit 8 is required for male meiosis

“…36.7% ( n = 30) of apc8‐1 meiocytes have disorderly in bivalent alignment (Fig. c), similar to the phenotype of the previously identified cdc20.1 mutant (Niu et al ., ). Even though some bivalents are not aligned at the metaphase I plate, the homologues still successfully segregate at anaphase I (Fig.…”

“…The timely removal of cohesin complexes by separase depends on the degradation of cyclin B1 by the APC/C (Hellmuth et al ., ; Sivakumar & Gorbsky, ). The misalignment of meiotic bivalents in apc8‐1 resembles the phenotype observed in cdc20.1 meiocytes (Niu et al ., ) in which cohesin establishment is normal. We analysed the distribution of Arabidopsis SYN1 (Cai et al ., ), a homologue of the yeast meiosis‐specific cohesin REC8 (Meiotic recombination‐deficient 8), in wild‐type and apc8‐1 meiotic chromosome spreads.…”