Biology subjects

Bulankova, P.

Publications and source records attributed to Bulankova, P..

6 recordsLinked to original sources

bioRxiv2021

B1-type cyclins control microtubule organization during cell division in Arabidopsis

Flowering plants contain a large number of cyclin families, each containing multiple members, most of which have not been characterized to date. Here, we analyzed the role of the B1 subclass of mitotic cyclins in cell cycle control during Arabidopsis development. While we reveal CYCB1;5 to be a pseudogene, the remaining four members were found to be expressed in dividing cells. Mutant analyses showed a complex pattern of overlapping, development-specific requirements of B1-type cyclins with CYCB1;2 playing a central role. The double mutant cycb1;1 cycb1;2 is severely compromised in growth, yet viable beyond the seedling stage, hence representing a unique opportunity to study the function of B1-type cyclin activity at the organismic level. Immunolocalization of microtubules in cycb1;1 cycb1;2 and treating mutants with the microtubule drug oryzalin revealed a key role of B1-type cyclins in orchestrating mitotic microtubule networks. Subsequently, we identified the GAMMA-TUBULIN COMPLEX PROTEIN 3-INTERACING PROTEIN 1 (GIP1/MOZART) as an in vitro substrate of B1-type cyclin complexes and further genetic analyses support an important role in the regulation of GIP1 by CYCB1s.

cell biology↗

bioRxiv2021

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

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 reduced level of CENH3 did not induce haploid plants in crosses with wild plants, indicating that differences in centromere size is not the key determinant of centromere-mediate genome elimination.

genetics↗

bioRxiv2020

Diurnal transcript profiling of the diatom Seminavisrobusta reveals adaptations to a benthic lifestyle

1Coastal regions contribute an estimated 20% of annual gross primary production in the oceans, despite occupying only 0.03% of their surface area. Diatoms frequently dominate coastal sediments, where they experience large variations in light regime resulting from the interplay of diurnal and tidal cycles. Here, we report on an extensive diurnal transcript profiling experiment of the motile benthic diatom Seminavis robusta. Nearly 90% (23,328) of expressed protein-coding genes and 66.9% (1124) of expressed long intergenic non-coding RNAs (lincRNAs) showed significant expression oscillations and are predominantly phasing at night with a periodicity of 24h. Phylostratigraphic analysis found that rhythmic genes are enriched in deeply conserved genes, while diatom-specific genes are predominantly associated with midnight expression. Integration of genetic and physiological cell cycle markers with silica depletion data revealed potential new silica cell wall associated gene families specific to diatoms. Additionally, we observed 1752 genes with a remarkable semidiurnal (12-h) periodicity, while the expansion of putative circadian transcription factors may reflect adaptations to cope with highly unpredictable external conditions. Taken together, our results provide new insights into the adaptations of diatoms to the benthic environment and serve as a valuable resource for diurnal regulation in photosynthetic eukaryotes. O_FIG_DISPLAY_L [Figure 1] M_FIG_DISPLAY C_FIG_DISPLAY

systems biology↗

bioRxiv2020

Mitotic interhomolog recombination drives genomic diversity in diatoms

Diatoms, an evolutionarily successful group of microalgae, display high levels of intraspecific variability in natural populations. However, the process generating such diversity is unknown. Here we estimated the variability within a natural diatom population and subsequently mapped the genomic changes arising within cultures clonally propagated from single diatom cells. We demonstrate that genome rearrangements and mitotic recombination between homologous chromosomes underlie clonal variability, resulting in haplotype diversity accompanied by the appearance of novel protein variants and loss of heterozygosity resulting in the fixation of alleles. The frequency of interhomolog mitotic recombination exceeds 4 out of 100 cell divisions and increases under environmental stress. We propose that this plastic response in the interhomolog mitotic recombination rate increases the evolutionary potential of diatoms, contributing to their ecological success. One Sentence SummaryRecombination between homologous chromosomes in diatom vegetative cells leads to extensive genomic diversity in clonal populations.

genomics↗

bioRxiv2020

Mating type specific transcriptomic response to sex inducing pheromone in the pennate diatom Seminavis robusta

Sexual reproduction is a fundamental phase in the life cycle of most diatoms. Despite its role as a source of genetic variation, it is rarely reported in nature and its molecular foundations remain largely unknown. Here, we integrate independent transcriptomic datasets, in order to prioritize genes responding to sex inducing pheromones (SIPs) in the pennate diatom Seminavis robusta. We observe marked gene expression changes associated with SIP treatment in both mating types, including an inhibition of S-phase progression, chloroplast division, mitosis and cell wall formation. Meanwhile, meiotic genes are upregulated in response to SIP, including a sexually induced diatom specific cyclin (dsCyc). Our data further suggest an important role for reactive oxygen species, energy metabolism and cGMP signaling during the early stages of sexual reproduction. In addition, we identify several genes with a mating type specific response to SIP, and link their expression pattern with physiological responses such as the production of the attraction pheromone diproline and mate-searching behaviour in MT+. Combined, our results provide a model for early sexual reproduction in pennate diatoms and significantly expand the suite of target genes to detect sexual reproduction events in natural diatom populations.

molecular biology↗

bioRxiv2020

The Seminavis robusta genome provides insights into the evolutionary adaptations of benthic diatoms

Benthic diatoms are the main primary producers in shallow freshwater and coastal environments, fulfilling important ecological functions such as nutrient cycling and sediment stabilization. However, little is known about their evolutionary adaptations to these highly structured but heterogeneous environments. Here, we report a reference genome for the marine biofilm-forming diatom Seminavis robusta, showing that gene family expansions are responsible for a quarter of all 36,254 protein-coding genes. Tandem duplications play a key role in extending the repertoire of specific gene functions, including light and oxygen sensing, which are probably central for its adaptation to benthic habitats. Genes differentially expressed during interactions with bacteria are strongly conserved in other benthic diatoms while many species-specific genes are strongly upregulated during sexual reproduction. Combined with re-sequencing data from 48 strains, our results offer new insights on the genetic diversity and gene functions in benthic diatoms.

bioinformatics↗