Replication stress, a hallmark of cancerous and pre-cancerous lesions, is linked to structural chromosomal aberrations. Recent studies demonstrated that it could also lead to numerical chromosomal instability (CIN). The mechanism, however, remains elusive. Here, we show that inducing replication stress in non-cancerous cells stabilizes spindle microtubules and favours premature centriole disengagement, causing transient multipolar spindles that lead to lagging chromosomes and micronuclei. Premature centriole disengagement depends on the G2 activity of the Cdk, Plk1 and ATR kinases, implying a DNA-damage induced deregulation of the centrosome cycle. Premature centriole disengagement also occurs spontaneously in some CIN+ cancer cell lines and can be suppressed by attenuating replication stress. Finally, we show that replication stress potentiates the effect of the chemotherapeutic agent taxol, by increasing the incidence of multipolar cell divisions. We postulate that replication stress in cancer cells induces numerical CIN via transient multipolar spindles caused by premature centriole disengagement.

No abstract

Exposure to Bacillus thuringiensis (Bt) toxins in low- and moderate-dose transgenic crops may induce sublethal effects and increase the rate of Bt resistance evolution, potentially compromising control efficacy against target pests. We tested this hypothesis using the fall armyworm Spodoptera frugiperda, a major polyphagous lepidopteran pest relatively tolerant to Bt notorious for evolving field-relevant resistance to single-gene Bt maize. Late-instar larvae were collected from Bt Cry1Ab and non-Bt maize fields in five locations in Brazil, and their offspring was compared for survival, development, and population growth in rearing environment without and with Cry1Ab throughout larval development. Larval survival on Cry1Ab maize leaves varied from 20 to 80% among the populations. Larvae reared on Cry1Ab maize had seven-day delay in development time in relation to control larvae, and such delay was shorter in offspring of armyworms from Cry1Ab maize. Population growth rates were 50–70% lower for insects continuously exposed to Cry1Ab maize relative to controls, showing the population-level effect of Cry1Ab, which varied among the populations and prior exposure to Cry1Ab maize in the field. In three out of five populations, armyworms derived from Bt maize reared on Cry1Ab maize showed higher larval weight, faster larval development and better reproductive performance than the armyworms derived from non-Bt maize, and one of these populations showed better performance on both Cry1Ab and control diets, indicating no fitness cost of the resistance trait. Altogether, these results indicate that offspring of armyworms that developed on field-grown, single-gene Bt Cry1Ab maize had reduced performance on Cry1Ab maize foliage in two populations studied, but in other three populations, these offspring had better overall performance on the Bt maize foliage than that of the armyworms from non-Bt maize fields, possibly because of Cry1Ab resistance alleles in these populations. Implications of these findings for resistance management of S. frugiperda in Bt crops are discussed.

Brevicoryne brassicae (L), Lipaphis erysimi (Kalt) and Myzus persicae (Sultzer) (Homoptera: Aphididae) form the aphid complex that causes great losses in Brassicaceae in tropical and subtropical regions. Knowledge of their population dynamics is important for the development of integrated pest management programmes. This study aimed to investigate the effects of cabbage phenology, climatic factors and natural enemies populations on the dynamics of these organisms, and the factors regulating their predators’ occurrence. The densities of aphids and their natural enemies and the climate were monitored for two years in 16 cabbage crops. The highest densities of the aphids occurred during periods of relative humidity (RH) drop, a condition that affects them positively. Regarding the predators, the factors affecting their abundance varied but RH was positively related to most of them. This study provides relevant insights into the factors that regulate the aphids in cabbage and for the decision‐making process of control of these severe pests.

No abstract

Mutations in the WDR62 gene cause primary microcephaly, a pathological condition often associated with defective cell division that results in severe brain developmental defects. The precise function and localization of WDR62 within the mitotic spindle is, however, still under debate, as it has been proposed to act either at centrosomes or on the mitotic spindle. Here we explored the cellular functions of WDR62 in human epithelial cell lines using both short-term siRNA protein depletions and long-term CRISPR/Cas9 gene knockouts. We demonstrate that WDR62 localizes at spindle poles, promoting the recruitment of the microtubule-severing enzyme katanin. Depletion or loss of WDR62 stabilizes spindle microtubules due to insufficient microtubule minus-end depolymerization but does not affect plus-end microtubule dynamics. During chromosome segregation, WDR62 and katanin promote efficient poleward microtubule flux and favor the synchronicity of poleward movements in anaphase to prevent lagging chromosomes. We speculate that these lagging chromosomes might be linked to developmental defects in primary microcephaly.

O cultivo do feijão consorciado é prática comum entre agricultores da Zona da Mata Mineira, os quais promovem a diversificação produtiva de suas áreas visando principalmente a produção de alimentos para consumo da família. Diagnósticos de projetos de extensão universitária identificaram agricultores familiares que, além do consorcio com café, utilizam leguminosas em pré-cultivo ao feijão para fins de adubação verde, incrementando os processos biológicos que contribuem para a complexidade e sustentabilidade dos agroecossistemas. Assim, objetivou-se avaliar espécies de leguminosas em pré-cultivo e sua influência sobre o feijoeiro em sistema de consórcio com cafeeiro, sob manejo da agricultura familiar. A avaliação foi conduzida em uma propriedade rural e conjuntamente com o agricultor familiar. As leguminosas avaliadas foram o feijão-de-porco e a lablabe, além de uma testemunha, representada pela vegetação espontânea. Foi adotado o delineamento de blocos casualizados, com oito repetições, onde cada entrelinha de cafeeiros representou um bloco. As variáveis analisadas foram produtividade de matérias fresca e seca; teor e acúmulo de N; contribuição da FBN nos pré-cultivos e produtividade do feijão cultivado em sucessão. O feijão-de-porco foi a leguminosa que apresentou a maior produção de matérias fresca e seca (19,04 e 4,25 t ha-1, respectivamente), acumulou mais N (113,99 kg ha-1) e aportou a maior quantidade de N-FBN ao sistema (49,18 kg ha-1). No entanto, o pré-cultivo com leguminosas não influenciou a produtividade do feijoeiro cultivado em sucessão.

Resumo. A Teca (Tectona grandis Linn. F.) é uma espécie arbórea oriunda do sudeste da Ásia que foi introduzida no Brasil nos anos 60. Atualmente seu cultivo está em franca expansão em vários estados. Apesar desta espécie apresentar relativa resistência, alguns insetos têm sido reportados em povoamentos homogêneos, com possibilidades de provocar perdas em sua produção. Foi observada a ocorrência de uma cigarrinha em teca no município de Paulistas, Minas Gerais, Brasil. A espécie Aethalion reticulatum Linnaeus (Hemiptera: Aethalionidae) foi encontrada em galhos e folhas de árvores com três anos de idade. A ocorrência dessa cigarrinha indica a colonização e adaptação por insetos nativos, que futuramente poderão alcançar o status de praga da cultura da teca.Occurrence of Aethalion reticulatum Linnaeus (Hemiptera: Aethalionidae) in Tectona grandis Linn. f. (Verbenaceae) in Minas Gerais, BrazilAbstract. Teca (Tectona grandis Linn. F.) is a tree species originating in Southeast Asia wich was introduced in Brazil in the 1960s. Currently, its cultivation is booming in several states. Although this species shows relative resistance, some insects have been reported in homogenous stands, with possibilities of causing losses in their production. It was observed the occurrence of a spittlebug in teak in the municipality of Paulistas, Minas Gerais, Brazil. The specie Aethalion reticulatum Linnaeus (Hemiptera: Aethalionidae) was found on branches and leaves of three years old trees. The occurrence of this spittlebug indicates colonization and adaptation by native insects, which may eventually reach the pest status of teak culture.