A CENH3 mutation promotes meiotic exit and restores fertility in SMG7-deficient Arabidopsis

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Authors

CAPITAO C. TANASA Sorin FULNEČEK Jaroslav RAXWAL Vivek Kumar AKIMCHEVA S. BULANKOVA P. MIKULKOVÁ Pavlína CRHÁK KHAITOVÁ Lucie KALIDASS M. LERMONTOVA I. SCHEIDID M. ŘÍHA Karel

Year of publication 2021
Type Article in Periodical
Magazine / Source PLoS Genetics
MU Faculty or unit

Central European Institute of Technology

Citation
Web https://journals.plos.org/plosgenetics/article?id=10.1371/journal.pgen.1009779
Doi http://dx.doi.org/10.1371/journal.pgen.1009779
Keywords CHROMOSOME SEGREGATION; MITOTIC EXIT; MEIOSIS-I; GENE; PROGRESSION; HOMOLOG; SMG7; SPOROGENESIS; INITIATION; EVOLUTION
Description Meiosis in angiosperm plants is followed by mitotic divisions to form multicellular haploid gametophytes. Termination of meiosis and transition to gametophytic development is, in Arabidopsis, governed by a dedicated mechanism that involves SMG7 and TDM1 proteins. Mutants carrying the smg7-6 allele are semi-fertile due to reduced pollen production. We found that instead of forming tetrads, smg7-6 pollen mother cells undergo multiple rounds of chromosome condensation and spindle assembly at the end of meiosis, resembling aberrant attempts to undergo additional meiotic divisions. A suppressor screen uncovered a mutation in centromeric histone H3 (CENH3) that increased fertility and promoted meiotic exit in smg7-6 plants. The mutation led to inefficient splicing of the CENH3 mRNA and a substantial decrease of CENH3, resulting in smaller centromeres. The reduced level of CENH3 delayed formation of the mitotic spindle but did not have an apparent effect on plant growth and development. We suggest that impaired spindle re-assembly at the end of meiosis limits aberrant divisions in smg7-6 plants and promotes formation of tetrads and viable pollen. Furthermore, the mutant with reduced level of CENH3 was very inefficient haploid inducer indicating that differences in centromere size is not the key determinant of centromere-mediated genome elimination.
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