The PsENOD12 Gene Is Expressed at Two Different Sites in Afghanistan Pea Pseudonodules Induced by Auxin Transport Inhibitors

A number of early nodulin genes are expressed in specific cell types as pea (Pisum sativum) root nodules develop. The Pisum sativum early nodulin PsENOD2 is detected only in the uninfected cells of the nodule parenchyma, whereas PsENOD12 is expressed at two spatially removed sites: in root hairs and adjacent cortical cells, both of which can be invaded by Rhizobium entering through infection threads, and in derivatives of newly divided root inner cortical cells that establish the nodule primordium. We tested whether Rhizobium infection is required for triggering PsENOD12 gene expression by inducing nodule-like structures on Afghanistan pea roots with the auxin transport inhibitor N-(1-naphthyl)phthalamic acid (NPA). These nodule-like structures lack infection threads but resemble Rhizobium-induced nodules in other aspects. For one, both PsENOD2 and PsENOD12 transcripts were detected in these structures. PsENOD2 mRNA was localized by in situ hybridization to a zone equivalent to the nodule parenchyma of Rhizobium-induced nodules, whereas PsENOD12 transcripts were detected in a group of cells comparable to the nodule primordium of developing nodules. In addition, PsENOD12 mRNA was detected in uninfected root hairs 48 h after NPA treatment. These results indicate that infection is not a trigger for PsENOD12 gene expression in Afghanistan pea and rather suggest that the expression of the PsENOD2 and PsENOD12 genes is correlated with the differentiation of specific cell types in the developing nodule

Positioning of Chromosomes in Human Spermatozoa Is Determined by Ordered Centromere Arrangement

<div><p>The intranuclear positioning of chromosomes (CHRs) is a well-documented fact; however, mechanisms directing such ordering remain unclear. Unlike somatic cells, human spermatozoa contain distinct spatial markers and have asymmetric nuclei which make them a unique model for localizing CHR territories and matching peri-centromere domains. In this study, we established statistically preferential longitudinal and lateral positioning for eight CHRs. Both parameters demonstrated a correlation with the CHR gene densities but not with their sizes. Intranuclear non-random positioning of the CHRs was found to be driven by a specific linear order of centromeres physically interconnected in continuous arrays. In diploid spermatozoa, linear order of peri-centromeres was identical in two genome sets and essentially matched the arrangement established for haploid cells. We propose that the non-random longitudinal order of CHRs in human spermatozoa is generated during meiotic stages of spermatogenesis. The specific arrangement of sperm CHRs may serve as an epigenetic basis for differential transcription/replication and direct spatial CHR organization during early embryogenesis.</p> </div

In human spermatozoa, nonhomologous centromeres are arranged in arrays with the fixed chromosome-specific linear order.

<p>(A) Visualization of CEN arrays using FISH with pan-CEN DNA probe. Nucleus borders, determined by DAPI staining are shown by a blue dashed line. (B) The outline of the sequential FISH procedure. First, cells were hybridized with pan-CEN probe (a, green). Cells that demonstrated unfolded CEN strings were subjected to sequential FISH with chromosome-specific peri-CEN probes (b–e). (f) - Artificial colors were assigned to the peri-CEN signals and images were merged. (g) - Schematic representation of the chromosome-specific peri-CEN localization. (C) Examples of CEN localization along sperm chromocenter arrays. (D) The cumulative scheme. (E) The order of CENs is preserved in diploid sperm nuclei. (a) Diploid sperm cells revealed using FISH with chromosome-specific peri-CEN probes; merged images after sequential FISH. (b) - Schematic representation of chromosome-specific peri-CEN localization. (c) - Cumulative scheme. Noteworthy, two sets of chromosomes have the same linear order matching with the arrangement established in haploid sperm nuclei (D). Scale bars in A–E – 5 µm.</p