Biology subjects

Elesawi, I. E.

Publications and source records attributed to Elesawi, I. E..

3 recordsLinked to original sources

bioRxiv2021

Interfered Chromosome Pairing Promotes Meiosis Instability of Autotetraploid Arabidopsis by High Temperatures

Alterations of environmental temperature affect multiple meiosis processes in flowering plants. Polyploid plants derived from whole genome duplication (WGD) have enhanced genetic plasticity and tolerance to environmental stress, but meanwhile face a challenge for organization and segregation of doubled chromosome sets. In this study, we investigated the impact of increased environmental temperature on male meiosis in autotetraploid Arabidopsis thaliana. Under low to mildly-increased temperatures (5-28{degrees}C), irregular chromosome segregation universally takes place in synthesized autotetraploid Columbia-0 (Col-0). Similar meiosis lesions occur in autotetraploid rice (Oryza sativa L.) and allotetraploid canola (Brassica napus cv. Westar), but not in evolutionary-derived hexaploid wheat (Triticum aestivum). As temperature increases to extremely high, chromosome separation and tetrad formation are severely disordered due to univalent formation caused by suppressed crossing-over. We found a strong correlation between tetravalent formation and successful chromosome pairing, both of which are negatively correlated with temperature elevation, suggesting that increased temperature interferes with crossing-over prominently by impacting homolog pairing. Besides, we showed that loading irregularities of axis proteins ASY1 and ASY4 co-localize on the chromosomes of syn1 mutant, and the heat-stressed diploid and autotetraploid Col-0, revealing that heat stress affects lateral region of synaptonemal complex (SC) by impacting stability of axis. Moreover, we showed that chromosome axis and SC in autotetraploid Col-0 are more sensitive to increased temperature than that of diploid Arabidopsis. Taken together, our study provide evidence suggesting that WGD without evolutionary and/or natural adaption negatively affects stability and thermal tolerance of meiotic recombination in Arabidopsis thaliana.

plant biology↗

bioRxiv2021

Mechanistic Insights of High Temperature-Interfered Meiosis in Autotetraploid Arabidopsis thaliana

Environmental temperature has a huge impact on multiple meiosis processes in flowering plants. Polyploid plants derived from whole genome duplication are believed to have an enhanced abiotic stress tolerance. In this study, the impact of high temperatures on male meiosis in autotetraploid Arabidopsis thaliana was investigated. We found that autotetraploid Columbia (Col-0) plants generate a subpopulation of aberrant meiotic products under normal temperature, which is significantly increased under heat stress. Cytological studies revealed that, as the case in diploid Arabidopsis thaliana, assembly of microtubular cytoskeleton network, pairing and segregation of homologous chromosomes, and meiotic recombination in autotetraploid Arabidopsis are compromised under the high temperatures. Immunostaining of {ramshorn}H2A.X and recombinase DMC1 suggested that heat stress inhibits formation of DNA double-strand breaks; additionally, it specifically destabilizes ASY1 and ASY4, but not SYN1 on chromosomes. The loading defects of ASY1 and ASY4 overlap in the syn1 mutant, which supports that the building of lateral element of synaptonemal complex occurs downstream of a SYN1-ASY4-ASY3 stepwise assembly of axis. Remarkably, heat-induced abnormalities of ASY1 and ASY4 co-localize on chromosomes of both diploid and autotetraploid Arabidopsis, suggesting that high temperatures interfere with ASY1-associated SC via an impacted stability of chromosome axis. Furthermore, ZYP1-dependent transverse filament of SC is disrupted by heat stress. Taken together, these findings suggest that polyploidization negatively contributes to instability of chromosome axis and meiotic recombination in Arabidopsis thaliana under heat stress.

plant biology↗

bioRxiv2020

Heat Stress Interferes with Formation of Double-Strand Breaks and Homology Synapsis in Arabidopsis thaliana

Meiotic recombination (MR) drives novel combination of alleles and contributes to genomic diversity in eukaryotes. In this study, we showed that heat stress (36-38{degrees}C) over fertile threshold fully abolished crossover (CO) formation in Arabidopsis. Cytological and genetic studies in wild-type plants, and the syn1 and rad51 mutants suggested that heat stress reduces generation of SPO11-dependent double-strand breaks (DSBs). In support, the abundance of recombinase DMC1, which is required for MR-specific DSB repair, was significantly reduced under heat stress. In addition, we showed that high temperatures induced disassembly and/or instability of ASY4-but not SYN1-mediated chromosome axis. At the same time, ASY1-associated lateral element of synaptonemal complex (SC) was partially affected, while the ZYP1-dependent central element of SC was disrupted, indicating that heat stress impairs SC formation. Moreover, quantitative RT-PCR revealed that genes involved in DSB formation; e.g. SPO11-1, PRD1, 2 and 3, were not impacted; however, recombinase RAD51 and chromosome axis factors ASY3 and ASY4 were significantly downregulated under heat stress. Taken together, these findings revealed that heat stress inhibits MR via compromised DSB formation and homolog synapsis, which are possible downstream effects of the impacted chromosome axis. Our study thus provides evidence shedding light on how increase of environmental temperature influences MR in Arabidopsis.

plant biology↗