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.

• MeSH
• aparát dělícího vřeténka MeSH
• Arabidopsis genetika   fyziologie   MeSH
• fertilita genetika   MeSH
• meióza genetika   MeSH
• messenger RNA genetika   MeSH
• mutace * MeSH
• proteiny huseníčku genetika   MeSH
• rostlinné geny * MeSH
• transportní proteiny genetika   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

In plants, gametogenesis occurs late in development, and somatic mutations can therefore be transmitted to the next generation. Longer periods of growth are believed to result in an increase in the number of cell divisions before gametogenesis, with a concomitant increase in mutations arising due to replication errors. However, there is little experimental evidence addressing how many cell divisions occur before gametogenesis. Here, we measured loss of telomeric DNA and accumulation of replication errors in Arabidopsis with short and long life spans to determine the number of replications in lineages leading to gametes. Surprisingly, the number of cell divisions within the gamete lineage is nearly independent of both life span and vegetative growth. One consequence of the relatively stable number of replications per generation is that older plants may not pass along more somatically acquired mutations to their offspring. We confirmed this hypothesis by genomic sequencing of progeny from young and old plants. This independence can be achieved by hierarchical arrangement of cell divisions in plant meristems where vegetative growth is primarily accomplished by expansion of cells in rapidly dividing meristematic zones, which are only rarely refreshed by occasional divisions of more quiescent cells. We support this model by 5-ethynyl-2'-deoxyuridine retention experiments in shoot and root apical meristems. These results suggest that stem-cell organization has independently evolved in plants and animals to minimize mutations by limiting DNA replication.

• MeSH
• akumulace mutací MeSH
• Arabidopsis genetika   růst a vývoj   MeSH
• diploidie MeSH
• genom rostlinný genetika   MeSH
• kořeny rostlin genetika   růst a vývoj   MeSH
• meristém genetika   růst a vývoj   MeSH
• mutace genetika   MeSH
• regulace genové exprese u rostlin MeSH
• replikace DNA genetika   MeSH
• rostlinné buňky MeSH
• sekvenční analýza DNA MeSH
• stonky rostlin genetika   růst a vývoj   MeSH
• výhonky rostlin genetika   růst a vývoj   MeSH
• zárodečné buňky růst a vývoj   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

The ability to analyze cell division in both spatial and temporal dimensions within an organism is a key requirement in developmental biology. Specialized cell types within individual organs, such as those within shoot and root apical meristems, have often been identified by differences in their rates of proliferation prior to the characterization of distinguishing molecular markers. Replication-dependent labeling of DNA is a widely used method for assaying cell proliferation. The earliest approaches used radioactive labeling with tritiated thymidine, which were later followed by immunodetection of bromodeoxyuridine (BrdU). A major advance in DNA labeling came with the use of 5-ethynyl-2'deoxyuridine (EdU) which has proven to have multiple advantages over BrdU. Here we describe the methodology for analyzing EdU labeling and retention in whole plants and histological sections of Arabidopsis.

• MeSH
• Arabidopsis cytologie   ultrastruktura   MeSH
• barvení a značení metody   MeSH
• deoxyuridin analogy a deriváty   analýza   MeSH
• DNA rostlinná analýza   MeSH
• kořeny rostlin ultrastruktura   MeSH
• meristém ultrastruktura   MeSH
• proliferace buněk * MeSH
• replikace DNA MeSH
• rostlinné buňky ultrastruktura   MeSH
• semenáček ultrastruktura   MeSH
• zalévání tkání do parafínu metody   MeSH
• Publikační typ
• časopisecké články MeSH

Nonsense-mediated mRNA decay (NMD) is a conserved eukaryotic RNA surveillance mechanism that degrades aberrant mRNAs. NMD impairment in Arabidopsis is linked to constitutive immune response activation and enhanced antibacterial resistance, but the underlying mechanisms are unknown. Here we show that NMD contributes to innate immunity in Arabidopsis by controlling the turnover of numerous TIR domain-containing, nucleotide-binding, leucine-rich repeat (TNL) immune receptor-encoding mRNAs. Autoimmunity resulting from NMD impairment depends on TNL signaling pathway components and can be triggered through deregulation of a single TNL gene, RPS6. Bacterial infection of plants causes host-programmed inhibition of NMD, leading to stabilization of NMD-regulated TNL transcripts. Conversely, constitutive NMD activity prevents TNL stabilization and impairs plant defense, demonstrating that host-regulated NMD contributes to disease resistance. Thus, NMD shapes plant innate immunity by controlling the threshold for activation of TNL resistance pathways.

• MeSH
• Arabidopsis genetika   imunologie   mikrobiologie   MeSH
• interakce hostitele a patogenu MeSH
• messenger RNA genetika   imunologie   MeSH
• nemoci rostlin genetika   imunologie   mikrobiologie   MeSH
• nesmyslný kodon MeSH
• nonsense mediated mRNA decay * MeSH
• proteiny huseníčku genetika   imunologie   MeSH
• Pseudomonas syringae genetika   fyziologie   MeSH
• receptory imunologické genetika   imunologie   MeSH
• RNA-helikasy genetika   imunologie   MeSH
• transportní proteiny genetika   imunologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH