DNA replication and chromosome positioning throughout the interphase in three dimensional space of plant nuclei

Abstract

20 21 E-mail addresses: 22 Němečková A. -nemeckova@ueb.cas.cz 23 Koláčková V. -kolackova@ueb.cas.cz 24 Vrána J. -jan.vrana@osu.cz 25 Doležel J. -dolezel@ueb.cas.cz 26 27 28 Highlight 29 Telomere and centromere replication timing and interphase chromosome positioning in seven 30 grass species differing in genome size indicates a more complex relation between genome size 31 and the chromosome positioning. 32 33 34 2 Abstract 35 Despite the recent progress, our understanding of the principles of plant genome organization 36 and its dynamics in three-dimensional space of interphase nuclei remains limited. In this 37 study, DNA replication timing and interphase chromosome positioning was analyzed in seven 38 Poaceae species differing in genome size. A multidisciplinary approach combining newly 39 replicated DNA labelling by EdU, nuclei sorting by flow cytometry, three-dimensional 40 immuno-FISH, and confocal microscopy revealed similar replication timing order for 41 telomeres and centromeres as well as for euchromatin and heterochromatin in all seven 42 species. The Rabl configuration of chromosomes that lay parallel to each other and their 43 centromeres and telomeres are localized at opposite nuclear poles, was observed in wheat, oat, 44 rye and barley with large genomes, as well as in Brachypodium with a small genome. On the 45 other hand, chromosomes of rice with a small genome and maize with relatively large genome 46 did not assume proper Rabl configuration. In all species, the interphase chromosome 47 positioning inferred from the location of centromeres and telomeres was stable throughout the 48 interphase. These observations extend earlier studies indicating a more complex relation 49 between genome size and interphase chromosome positioning, which is controlled by factors 50 currently not known. 51 52 53 65 Interestingly, a different arrangement of chromosomes in interphase nuclei was 66 observed in Arabidopsis thaliana, a model plant with small genome (1C~157 Mbp). Here, the 67 centromeres are located at the nuclear periphery, whereas the telomeres congregate around 68 3 nucleolus (Armstrong et al., 2001; Fransz et al., 2002). Centromeric heterochromatin forms 69 dense bodies called chromocenters, while euchromatin domains form 0.2 -2 Mb loops that 70 are organized into Rosette-like structures (Fransz et al., 2002; Pecinka et al., 2004; Tiang et 71 al., 2012; Schubert et al., 2014). 72 Some earlier studies suggested that chromatin arrangement in interphase nuclei of 73 wheat, oat and rice, and in particular the centromere -telomere orientation, may be tissue-74 specific and cell cycle-dependent (Dong and Jiang 1998; Prieto et al., 2004; Santos and Show, 75 2004). While a majority of nuclei in somatic cells of rice (Oryza sativa), which has a small 76 genome (1C~490 Mbp, Bennett et al., 1976) lack Rabl configuration, chromosomes in the 77 nuclei of some rice tissues, e.g., pre-meiotic cells in anthers or xylem -vessel precursor cells 78 seem to assume the configuration (Prieto et al., 2004; San...

Association of DNA biosynthesis with planting value enhancement in hydroprimed maize seeds

“…Several studies have documented that seed priming causes an enhancement in the nuclear DNA content from 2C to 4C in radicle meristem cells, which signify advancement of G 1 phase to the S or G 2 phases of the cell cycle ( Vázquez-Ramos and Sánchez, 2003 ; ( Vázquez-Ramos and Sánchez, 2007 ) Alžběta et al, 2020 ). Mean germination time was significantly correlated with increase in 4C nuclei in pepper ( Capsicum annum L.) and tomato ( Lycopersicon esculentum Mill.)…”