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.

The karyotype is a basic concept regarding the genome, fundamentally described by the number and morphological features of all chromosomes. Chromosome class, centromeric index, intra- and interchromosomal asymmetry index, and constriction localization are important in clinical, systematic and evolutionary approaches. In spite of the advances in karyotype characterization made over the last years, new data about the chromosomes can be generated from quantitative methods, such as image cytometry. Therefore, using Zea mays L., this study aimed to update the species’ karyotype by supplementing information on chromosome DNA sizing. After adjustment of the procedures, chromosome morphometry and class as well as knob localization enabled describing the Z. mays karyotype. In addition, applying image cytometry, DNA sizing was unprecedentedly measured for the arms and satellite of all chromosomes. This way, unambiguous identification of the chromosome pairs, and hence the assembly of 51 karyograms, were only possible after the DNA sizing of each chromosome, their arms and satellite portions. These accurate, quantitative and reproducible data also enabled determining the distribution and variation of DNA content in each chromosome. From this, a correlation between DNA amount and total chromosome length evidenced that the mean DNA content of chromosome 9 was higher than that of chromosome 8. The chromosomal DNA sizing updated the Z. mays karyotype, providing insights into its dynamic genome with regards to the organization of the ten chromosomes and their respective portions. Considering the results and the relevance of cytogenetics in the current scenario of comparative sequencing and genomics, chromosomal DNA sizing should be incorporated as an additional parameter for karyotype definition. Based on this study, it can be affirmed that cytogenetic approaches go beyond the simple morphological description of chromosomes.

Painting plant chromosomes through chromosomal in situ suppression (CISS) hybridization has long been considered impracticable. Seeking to build specific and complex probes from a single microdissected chromosome, we employed human chromosomes as models to standardize all the necessary steps for application in plants. Human metaphases were used to define the adequate conditions for microdissection, chromosome DNA amplification and labeling through degenerate oligonucleotideprimed PCR, and in situ hybridization stringency. Subsequently, these methodologies were applied in the plant species Zea mays (chromosome 1) and Capsicum annuum (chromosome 7 or 8). The high quality of human and plant cytogenetic preparations and the meticulous standardization of each step, especially the most critical onesmicrodissection and first round of DNA amplification -were crucial to eliminate the signs of non-specific hybridization and for direct application in plants. By overcoming these challenges, we obtained chromosome-specific probes, which allowed to achieve a clear and uniform painting of the entire target chromosomes with little or no background, evidencing their complexity and specificity. Despite the high amount of ubiquitous repetitive sequences in plant genomes, the main drawback for chromosome painting, we successfully employed our methodology on two plant species. Both have more than 80% repetitive sequences, which is compared to the human genome (66-69%). This is the first time that plant chromosome-specific probes were successfully obtained from a single A mitotic or meiotic microdissected chromosome. Thereby, we assume that chromosome painting through microdissection and CISS hybridization can now be considered a reality in the field of plant cytogenetics.

The mosquito Aedes aegypti (Diptera: Culicidae) is the main vector of human arborvirus in Brazil. Oviposition behavior is important for the survival and dispersal of A. aegypti. The objective of this study was to evaluate the oviposition behavior and its relationship to meteorological factors. Twenty ovitraps were installed in two neighborhoods in the urban area of the city of Salinas, MG, southeastern Brazil. The traps were inspected weekly for the presence of eggs in the water and on the paddle. Simultaneously, regional weather data were analyzed. The results showed the Ovitrap Positivity Index (OPI) varied greatly, from 0 to 90%, between the weeks and boroughs sampled, demonstrating the vector's great population fluctuation. Among the analyzed climatic factors, rainfall strongly influenced oviposition, followed by relative air humidity. The number of eggs found on the paddle was significantly higher than in the water (p<0.05). However, a significant increase of eggs in the water was noticed when the relative humidity dropped below 40%. This seems to be an important behavior to maintain the population in periods of drought. Through the low number of eggs (<30) found in 56% of positive traps, we concluded that skip-oviposition behavior occurred, contributing to the prevalence of mosquitoes during the sampled period. It is concluded that the occurrence of water oviposition may be higher than described in the literature, and should be studied due to its evolutionary and epidemiological importance.

LTR-retrotransposons, knobs and structural chromosome alterations contribute to shape the structure and organization of the Zea mays karyotype. Our initial nuclear DNA content data of Z. mays accessions revealed an intraspecific variation (2 C = 2.00 pg to 2 C = 6.10 pg), suggesting differences in their karyotypes. We aimed to compare the karyotypes of three Z. mays accessions in search of the differences and similarities among them. Karyotype divergences were demonstrated among the accessions, despite their common chromosome number (2n = 20) and ancestral origin. Cytogenomic analyses showed that repetitive sequences and structural chromosome alterations play a significant role in promoting intraspecific nuclear DNA content variation. In addition, heterozygous terminal deletion in chromosome 3 was pointed out as a cause of lower nuclear 2 C value. Besides this, translocation was also observed in the short arm of chromosome 1. Differently, higher 2 C value was associated with the more abundant distribution of LTR-retrotransposons from the family Grande in the karyotype. Moreover, heteromorphism involving the number and position of the 180-bp knob sequence was found among the accessions. Taken together, we provide insights on the pivotal role played by repetitive sequences and structural chromosome alterations in shaping the karyotype of Z. mays.