A large percentage of eukaryotic genomes consist of repetitive DNA that plays an important role in the organization, size and evolution. In the case of crickets, chromosomal variability has been found using classical cytogenetics, but almost no information concerning the organization of their repetitive DNAs is available. To better understand the chromosomal organization and diversification of repetitive DNAs in crickets, we studied the chromosomes of two Gryllidae species with highly divergent karyotypes, i.e., 2n(♂) = 29,X0 (Gryllus assimilis) and 2n = 9, neo-X1X2Y (Eneoptera surinamensis). The analyses were performed using classical cytogenetic techniques, repetitive DNA mapping and genome-size estimation. Conserved characteristics were observed, such as the occurrence of a small number of clusters of rDNAs and U snDNAs, in contrast to the multiple clusters/dispersal of the H3 histone genes. The positions of U2 snDNA and 18S rDNA are also conserved, being intermingled within the largest autosome. The distribution and base-pair composition of the heterochromatin and repetitive DNA pools of these organisms differed, suggesting reorganization. Although the microsatellite arrays had a similar distribution pattern, being dispersed along entire chromosomes, as has been observed in some grasshopper species, a band-like pattern was also observed in the E. surinamensis chromosomes, putatively due to their amplification and clustering. In addition to these differences, the genome of E. surinamensis is approximately 2.5 times larger than that of G. assimilis, which we hypothesize is due to the amplification of repetitive DNAs. Finally, we discuss the possible involvement of repetitive DNAs in the differentiation of the neo-sex chromosomes of E. surinamensis, as has been reported in other eukaryotic groups. This study provided an opportunity to explore the evolutionary dynamics of repetitive DNAs in two non-model species and will contribute to the understanding of chromosomal evolution in a group about which little chromosomal and genomic information is known.

The stingless bees of the genus Melipona comprise a group with approximately 40 Neotropical species. Despite their ecological and economic importance, the size of the genomes of these species remains poorly known. Thus, the present study measured the DNA content of 15 Melipona species. The mean genome size (1C) of the females ranged from 0.27 pg to 1.38 pg, with increments of, approximately, 0.12 pg. It was possible to recognize two groups of species: the first presented relatively low DNA content (average = 0.29 pg), while the second showed high DNA content (average = 0.98 pg). This result corroborates the cytogenetic classification of these species into two groups, one of them comprising species with a low heterochromatin content (<50%), and the other species with high heterochromatin content (>50%). Amongst the groups with low and high DNA content, there was no significant correlation between the DNA content and the size of the bees. The data obtained may aid in the selection of species which are suitable for sequencing projects, besides providing an overview of the diversity in the genome size of the Melipona genus. flow cytometry / genome size / Hymenoptera / Melipona

Genome size estimates and their evolution can be useful for studying the phylogenetic relationships and taxonomy of a particular group. In the present study, the genome sizes of the three species that comprise the Mycetophylax genus were estimated by flow cytometry (FCM). There was little variation in genome size among them. The mean haploid genome size value of male and female individuals of Mycetophylax morschi was 312.96 Mbp (0.32 pg) and that of Mycetophylax conformis and Mycetophylax simplex females were 312.96 Mbp (0.32 pg) and 381.42 Mbp (0.39 pg), respectively. At first glance, this variation could be related with the heterochromatin content. Our results, together with other previous reports, have contributed to our knowledge about Attini genome size and will be useful to improve the understanding of the evolution of this tribe. It will help select potential model species in Attini for future genomic and sequencing projects.

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The first studies on the genome size of stingless bee species showed a range from 0.27 pg (Melipona subnitida and Melipona quadrifasciata) to 1.38 pg (Melipona capixaba). Considering this variation, we quantified the DNA content of 26 species of Meliponini, in order to provide input for future comparative studies in this tribe. Haploid genome size (1C) estimates, using flow cytometry analyses (FCM), ranged from 0.26±0.003 pg (Paratrigona subnuda) to 0.98±0.023 pg (Melipona flavolineata), with an average of 0.54±0.17 pg. FCM analyses also demonstrated a small difference in the haploid genome size between males and females of the same species, with the males generally having a smaller genome than females. Our data also evidenciated that variations in the genome size of stingless bees do not correlate with changes in chromosome number and that in some genera the DNA content is more variable than in others.

Cadmium (Cd2+) is highly harmful to plant growth. Although Cd2+ induces programmed cell death (PCD) in plant cells, Cd2+ stress in whole plants during later developmental stages and the mechanism underlying Cd2+‐mediated toxicity are poorly understood. Here, we showed that Cd2+ limits plant growth, causes intense redness in leaf vein, leaf yellowing, and chlorosis during the R1 reproductive stage of soybean (Glycine max). These symptoms were associated with Cd2+‐induced PCD, as Cd2+‐stressed soybean leaves displayed decreased number of nuclei, enhanced cell death, DNA damage, and caspase 1 activity compared to unstressed leaves. Accordingly, Cd2+‐induced NRPs, GmNAC81, GmNAC30 and VPE, the DCD/NRP‐mediated cell death signalling components, which execute PCD via caspase 1‐like VPE activity. Furthermore, overexpression of the positive regulator of this cell death signalling GmNAC81 enhanced sensitivity to Cd2+ stress and intensified the hallmarks of Cd2+‐mediated PCD. GmNAC81 overexpression enhanced Cd2+‐induced H2O2 production, cell death, DNA damage, and caspase‐1‐like VPE expression. Conversely, BiP overexpression negatively regulated the NRPs/GmNACs/VPE signalling module, conferred tolerance to Cd2+ stress and reduced Cd2+‐mediated cell death. Collectively, our data indicate that Cd2+ induces PCD in plants via activation of the NRP/GmNAC/VPE regulatory circuit that links developmentally and stress‐induced cell death.

When working at quantifying the genome size of stingless bees, it was observed that males of Lestrimelitta sp possessed the same amount of nuclear DNA as the females. Thus, we used flow cytometry (FCM) and cytogenetic analysis to confirm the ploidy of these individuals. The males analyzed proved to be diploid, since, through cytometric analysis, it was demonstrated that the mean genome size of both males and females was the same (C = 0.463 pg), and, furthermore, cytogenetic analysis demonstrated that both had 2n = 28 chromosomes.

Chromosome-specific probes have been widely used in molecular cytogenetics, being obtained with different methods. In this study, a reproducible protocol for construction of chromosome-specific probes is proposed which associates in situ amplification (PRINS), micromanipulation and degenerate oligonucleotide-primed PCR (DOP-PCR). Human lymphocyte cultures were used to obtain metaphases from male and female individuals. The chromosomes were amplified via PRINS, and subcentromeric fragments of the X chromosome were microdissected using microneedles coupled to a phase contrast microscope. The fragments were amplified by DOP-PCR and labeled with tetramethyl-rhodamine-5-dUTP. The probes were used in fluorescent in situ hybridization (FISH) procedure to highlight these specific regions in the metaphases. The results show one fluorescent red spot in male and two in female X chromosomes and interphase nuclei.