Caracterização molecular e patogênica de isolados de Xanthomonas albilineans (Ashby) Dowson, agente causal da escaldadura das folhas da cana-de-açúcar Molecular and pathogenic characterization of isolates of Xanthomonas albilineans (Ashby) Dowson, causal agent of sugarcane leaf scald

A escaldadura das folhas, causada pela bactéria Xanthomonas albilineans (Ashby) Dowson, é uma das cinco doenças mais importantes da cana-de-açúcar e sua ocorrência reduz o rendimento e a longevidade da cultura. Variedades resistentes têm sido usadas para o controle, porém há evidências da ocorrência de variantes do patógeno. Em campos comerciais do Estado de São Paulo, tem sido observado que a mesma variedade de cana se apresenta como resistente em uma região e suscetível em outra, sugerindo a ocorrência de variantes na população do patógeno. Assim, o objetivo deste trabalho foi investigar a presença de diversidade genética da bactéria em áreas comerciais. Um total de 50 isolados foram obtidos em cultura pura a partir de plantas sintomáticas coletadas em Piracicaba (SP), Jaú (SP), região de Ribeirão Preto (SP) e Iturama (MG). Os isolados foram confirmados como pertencentes à espécie X. albilineans por meio de características de colônias, serologia e PCR com 'primers' específicos. Para caracterização da diversidade genética, foi usado o método de Rep-PCR, a partir do DNA extraído de cada isolado. Oito isolados, provenientes dos diferentes grupos identificados por rep-PCR, foram usados em testes de patogenicidade, por meio de inoculação em duas variedades de cana. Os resultados confirmaram todos os isolados como pertencentes à espécie X. albilineans. Por meio de rep-PCR, foi demonstrada diversidade genética entre os isolados, os quais foram separados em três grupos: um grupo composto somente pelos isolados de Piracicaba; um segundo, contendo todos os isolados amostrados em Jaú e na região de Ribeirão Preto, e um isolado de Iturama; e, no terceiro, somente dois isolados coletados em Iturama. Os testes de patogenicidade revelaram diferenças na agressividade entre isolados, porém sem relação com sua região de origem. Este trabalho revelou a ocorrência de diversidade genética e de agressividade dentro da espécie X. albilineans, evidenciando uma possível relação entre ocorrência de variantes do patógeno e reação de variedades de cana cultivadas no estado de São Paulo.<br>Leaf scald is among the five more important diseases in sugarcane and its occurrence reduces yield and crop longevity. Resistant cultivars have been used to control the disease, but there is evidences of the occurrence of variants of the pathogen. In commercial fields located in São Paulo State, it has been observed that one sugarcane cultivar can show symptoms in some regions but not in anothers, suggesting the presence of variants within the pathogen population. Thus, the aim of this study was to investigate the presence of genetic diversity of the bacteria in commercial areas. A total of 50 isolates were obtained in pure culture from symptomatic plants collected in 'Piracicaba (SP)', 'Jaú (SP)', 'Ribeirão Preto (SP)' region and 'Iturama (MG)'. The isolates were confirmed as X. albilineans by using characteristics such as of colony type, serology and PCR with specific primers. Rep-PCR method was used to evaluate genetic diversity using DNA extracted from each isolate. Eight isolates, from different groups identified by rep-PCR, were used in assays for pathogenicity by inoculation on two sugarcane cultivars. The results confirmed that all isolates belonged to X. albilineans. By using rep-PCR it was demonstrated the occurrence of genetic diversity among the isolates, which were separated in three groups: group 1- isolates only from 'Piracicaba'; group 2- isolates sampled in 'Jaú,' the isolates collected in 'Ribeirão Preto' region and one isolate from Iturama; and group 3 - two isolates from 'Iturama'. Assays for pathogeneicity revealed differences in agressivity among isolates, but not related to regions where they were collected. This study revealed the occurrence of genetic and agressivity diversity within X. albilineans population suggesting a possible relationship between occurrence of bacteria variants and reaction of sugarcane cultivars grown in São Paulo State

Outstanding nobility observed in Cu5 clusters reveals the key role of collective quantum effects

21 pags., 5 figs.Subnanometer-sized metal clusters often feature a molecule-like electronic structure, which makes their physical and chemical properties significantly different from those of nanoparticles and bulk material. Considering potential applications, there is a major concern about their thermal stability and susceptibility towards oxidation. Cu clusters of only 5 atoms (Cu5 clusters) are first synthesized in high concentration using a new-generation wet chemical method. Next, it is shown that, contrary to what is currently assumed, Cu5 clusters display nobility, beyond resistance to irreversible oxidation, at a broad range of temperatures and oxygen pressures. The outstanding nobility arises from an unusual reversible oxidation which is observed by in situ X-ray Absorption Spectroscopy and X-ray Photoelectron Spectroscopy on Cu5 clusters deposited onto highly oriented pyrolitic graphite at different oxygen pressures and up to 773 K. This atypical property is explained by a theoretical approach combining different state-of-the-art first principles theories. It reveals the essential role of collective quantum effects in the physical mechanism responsible for the nobility of Cu5 clusters, encompassing a structural ‘breathing’ through concerted Cu–Cu elongations/contractions upon O2 uptake/release, and collective charge transfer as well. A predictive phase diagram of their reversible oxidation states is also delivered, agreeing with the experimental observations. The collective quantum effects responsible of the observed nobility are expected to be general in subanometer-sized metal clusters, pushing this new generation of materials to an upper level.This work has been partly supported by the European Union’s Horizon 2020 Research and Innovation Programme un-der Grant Agreement No. 825999; the Spanish Agencia Estatal de Investigación (AEI) and the Fondo Europeo de Desarrollo Regional (FEDER, UE) under Grant No. MAT2016-75354-P; the Austrian Science Fund (FWF) under Grant P29893-N36; the CMST COST Action CM1405 “Molecules in Motion” (MOLIM); the Xunta de Galicia, Spain (Grupos Ref. Comp.ED431C 2017/22 and AEMAT ED431E 2018/08); Obra Social Fundación La Caixa: Ref.LCF/PR/PR12/11070003; ANPCyT PICT (2017-1220 and 2017-3944) and UNLP (Project11/X790), Argentina.N

A genome-wide association study identifies novel gene associations with facial skin wrinkling and mole count in Latin‐Americans

Background Genome-wide association studies (GWASs) have identified genes influencing skin ageing and mole count in Europeans, but little is known about the relevance of these (or other genes) in non-Europeans. Objectives To conduct a GWAS for facial skin ageing and mole count in adults < 40 years old, of mixed European, Native American and African ancestry, recruited in Latin America. Methods Skin ageing and mole count scores were obtained from facial photographs of over 6000 individuals. After quality control checks, three wrinkling traits and mole count were retained for genetic analyses. DNA samples were genotyped with Illumina’s HumanOmniExpress chip. Association testing was performed on around 8 703 729 single-nucleotide polymorphisms (SNPs) across the autosomal genome. Results Genome-wide significant association was observed at four genome regions: two were associated with wrinkling (in 1p13·3 and 21q21·2), one with mole count (in 1q32·3) and one with both wrinkling and mole count (in 5p13·2). Associated SNPs in 5p13·2 and in 1p13·3 are intronic within SLC45A2 and VAV3, respectively, while SNPs in 1q32·3 are near the SLC30A1 gene, and those in 21q21·2 occur in a gene desert. Analyses of SNPs in IRF4 and MC1R are consistent with a role of these genes in skin ageing. Conclusions We replicate the association of wrinkling with variants in SLC45A2, IRF4 and MC1R reported in Europeans. We identify VAV3 and SLC30A1 as two novel candidate genes impacting on wrinkling and mole count, respectively. We provide the first evidence that SLC45A2 influences mole count, in addition to variants in this gene affecting melanoma risk in Europeans