Short-distance pollen dispersal for an outcrossed, wind-pollinated southern beech (Nothofagus nervosa (Phil.) Dim. et Mil.)

The mating system (outcrossing, selfing, and biparental inbreeding) and the extent of pollen flow are two of the most important genetic features that determine the genetic structure of plant populations, and both are crucial for the design of conservation strategies. The objectives here were to estimate mating system parameters and to fit the pollen dispersal kernel for the southern beech, Nothofagus nervosa. We sampled 25 mothers and 372 progeny from two stands in the Tromen Lake region of Argentina. We registered spatial positions of the maternal trees, and genotyped mothers and offspring for five simple sequence repeat markers. We estimated single-locus (t _s?=?0.95) and multilocus (t _m?=?0.99) outcrossing rates and biparental inbreeding (t _m-t _s?=?0.04). The species is strongly outcrossing, but correlated paternity within maternal sibships (r _p?=?0.10) indicates that each maternal parent is sampling a different and restricted array of pollen donors. We used two protocols (twogener and kindist) to fit an exponential power dispersal kernel to the structure of pollen clouds sampled by different mothers. The estimated effective number of pollen donors contributing to a single mother was N _ep?=?9.9. The twogener and kindist analyses yielded slightly different estimates, but both indicated short average distances for pollen dispersal (<35?m), indicating that the dispersal kernel was strongly leptokurtic (???=?0.36). While short-distance pollen dispersal predominates, there remains a nontrivial probability of long-distance dispersal. The results are discussed in the context of ongoing conservation and management programs.     

Transmission efficiency of Xylella fastidiosa by sharpshooters (Hemiptera: Cicadellidae) in coffee and citrus

Xylella fastidiosa (Wells, Raju, Hung, Weisburg, Mandelco-Paul, and Brenner) is a bacterial pathogen transmitted by several sharpshooters in two tribes of Cicadellinae (Proconiini and Cicadellini). Here, we compared the transmission efficiency of X. fastidiosa in coffee (Coffea arabica L.) and citrus [Citrus sinensis (L.) Osbeck] by Cicadellini [Bucephalogonia xanthophis (Berg) and Dilobopterus costalimai Young] and Proconiini [Homalodisca ignorata Melichar and Oncometopia facialis (Signoret)] sharpshooters that occur in both crops. At different seasons, healthy adults of each species were submitted to a 48-h acquisition access period on citrus or coffee source plants infected with X. fastidiosa isolates that cause Citrus variegated chlorosis (CVC) and Coffee leaf scorch (CLS), respectively, and then confined on healthy seedlings of the corresponding host plant for a 48-h inoculation access period. No significant effect of inoculation season was observed when comparing infection rates of citrus or coffee plants inoculated by vectors at different times of the year. In citrus, the transmission rate by single insects was significantly higher for H. ignorata (30%) in relation to B. xanthophis (5%) and O. facialis (1.1%), but there was no difference among vector species in coffee, whose transmission rates ranged from 1.2 to 7.2%. Comparing host plants, H. ignorata was more effective in transmitting X. fastidiosa to citrus (30%) in relation to coffee (2.2%), whereas the other vectors transmitted the bacterium to both hosts with similar efficiencies. Despite these variations, vector efficiency in coffee and citrus is lower than that reported in other hosts.     

The effect of volcanism on postglacial migration and seed dispersal. A case study in southern South America

During the Quaternary, southern South American temperate forests were confined to small and isolated refugia. Recolonization could be related not only with location of refugia but also with postglacial phenomena like volcanism, which could have interrupted the expansion of the forests. The aim of this study was to analyze the local effect of volcanism during the postglacial migration of Nothofagus nervosa in a particular region of Argentina were convergence of two migratory routes was suggested. The main question is whether admixture occurred or not and if the current populations are connected by pollen or seed gene flow. Two populations separated by a 3-km-width lava flow were sampled. Buds from 30 individuals of each of the two populations and from a total of 142 juveniles were analyzed. Genetic variation was detected through maternally inherited chloroplast deoxyribonucleic acid (cpDNA; polymerase chain reaction restriction fragment length polymorphisms of two fragments) and nuclear markers like isozymes (six loci) and simple sequence repeats (three loci). Population genetic parameters were estimated and the existence of a genetic structure was tested with an analysis of molecular variance. Historical gene flow was estimated through the indirect method of the genetic differentiation (F _ST). Chloroplast DNA revealed a total genetic differentiation between the two populations indicating completely isolation respecting seed gene flow. On the contrary, the degree of genetic differentiation for the nuclear markers was significantly lower, and moderate levels of historical gene flow through pollen were inferred. The results suggest that in this area, volcanism has played an important local role during the expansion of N. nervosa maintaining these two populations separated. Communicated by A. Kremer     

Complexation of the mycotoxin zearalenone with β-cyclodextrin: Study of the interaction and first promising applications

This work reports the study of the interactions between native and substituted β-cyclodextrins and zearalenone and its derivatives α- and β-zearelonol. The data obtained by fluorescence and NMR experiments suggested that zearalenone, α- and β-zearalenol and cyclodextrins give rise to host-guest complexation, with the inclusion of the phenolic moiety inside the cyclodextrin cavity. The high stability of these complexes induces a high fluorescence enhancement upon complexation. These results have been successfully applied to the spectrofluorimetric determination of zearalenone in maize raw samples, without any chromatographic separation. Presented at the 29^th Mykotoxin-Workshop, Fellbach, Germany, May 14–16, 2007 Financial support: Emilia-Romagna region (project SIQUAL)     

Heterogeneous production of metallo-type peptidases in parasites belonging to the family Trypanosomatidae

Proteolytic enzymes play a central role in the physiology of all living organisms, participating in several metabolic pathways and in different phases of parasite-host interactions. We have identified cell-associated peptidase activities in 33 distinct flagellates, including representatives of almost all known trypanosomatid genera parasitizing insects (Herpetomonas, Crithidia, Leishmania, Trypanosoma, Leptomonas, Phytomonas, Blastocrithidia and Endotrypanum) as well as the biflagellate kinetoplastid Bodo, by using SDS-PAGE containing gelatin as co-polymerized substrate and proteolytic inhibitors. Under the alkaline pH (9.0) conditions employed, all the flagellates presented at least one peptidase, with the exception of Crithidia acanthocephali and Phytomonas serpens, which did not display any detectable proteolytic enzyme activity. All the proteolytic activities were completely inhibited by 1,10-phenanthroline, a zinc-chelating agent, putatively identifying these activities as metallo-type peptidases. EDTA and EGTA, two other metallopeptidase inhibitors, E-64 (a cysteine peptidase inhibitor), pepstatin A (an aspartyl peptidase inhibitor) and PMSF (a serine peptidase inhibitor) did not interfere with the metallopeptidase activities detected in the studied trypanosomatids. Conversely, Bodo-derived peptidases were resistant to 1,10-phenanthroline and only partially inhibited by EDTA, showing a distinct inhibition profile. Together, our data demonstrated great heterogeneity of expression of metallopeptidases in a wide range of parasites belonging to the family Trypanosomatidae.     

The combined role of glaciation and hybridization in shaping the distribution of genetic variation in a Patagonian southern beech

Aim The distribution of the genetic variation in long‐lived species is a combination of both, historical and current processes. In Nothofagus nervosa (Phil.) Dim. et Mil., the possible existence of multiple glacial refugia, the unidirectional gene flow along fragmented areas and the natural hybridization with the related species Nothofagus obliqua (Mirb.) Oerst. highlights as the most important factors responsible for modelling its genetic structure. The present study aims to find out the relative importance of these evolutionary processes in determining the distribution pattern of the genetic variation in N. nervosa. Location The study was carried out in north‐western Patagonia, Argentina. Twenty populations covering the entire distribution range of N. nervosa in Argentina were analysed. For comparison purposes, three populations from Chile were also included. Methods Genetic variation was detected using isozyme gene markers; diversity and differentiation parameters were calculated. A cluster analysis was performed and the correlation between genetic and geographical distances was tested. Results Levels of genetic variation were relatively high given the small distribution range of the species in Argentina. Genetic and geographical distances were not correlated and a longitudinal trend in the genetic variation was evident. Hotspots of diversity with rare and private alleles were observed among western populations, while hybrid seeds were found almost exclusively among eastern populations. Main conclusions The higher level of diversity observed in western populations could be related with the location of glacial refugia. Furthermore, it should also reflect low levels of gene flow given the eastward unidirectional winds. On the contrary, ancient and current interspecific hybridization processes would mainly cause the particular genetic constitution of the eastern populations. Evidence is presented supporting that glaciations and hybridization were the main factors shaping the distribution of the genetic variation in N. nervosa.     

Effects of marigold on the behavior,survival and nutrient reserves of <Emphasis Type="Italic">Aphidius Platensis</Emphasis>

Marigolds (Tagetes erecta L.) suppress nematodes and are attractive companion plants, but their role in biological control is unknown. We evaluated how exposure to marigold blooms impacts the aphid parasitoid, Aphidius platensis Brethes. Female wasps previously exposed to marigold spent more time walking and parasitizing Myzus percisae Sulzer or Schizaphis graminum Rodani aphids, and subsequently had higher parasitism rates. Meanwhile, completely starved wasps spent more time stationary and marginally more time grooming. Time spent probing, emergence rate, and sex ratio were not affected. Wasp survival was best on honey, followed by marigold, and lowest on non-blooming marigolds. Nutrient reserves of wasps given honey, aphid-infested marigold, or marigold alone were compared to newly-emerged unfed wasps. Their resulting lipid, glycogen and sugar levels were similar, suggesting that these foods helped wasps maintain reserves similar to emergence levels. These results suggest that marigold may improve biological control of aphids by A. platensis.     

A special issue of Biophysical Reviews dedicated to the 20th IUPAB (virtual) Congress “in” Foz do Iguaçu

The 20th IUPAB Congress took place online, together with the annual meetings of the Brazilian Biophysical Society and the Brazilian Society for Biochemistry and Molecular Biology, from the 4th to the 8th of October, 2021. The ten keynote lectures, 24 symposia, two poster sessions, and a series of technical seminars covered the full diversity of current biophysical research and its interfaces with other fields. The event had over 1000 attendees, with an excellent gender balance. Although the Americas dominated, there were also significant numbers of participants from Europe, Asia, and Africa.

The International Union of Pure and Applied Biophysics (IUPAB) came into existence in Stockholm in 1961 and has been a member of the International Science Council since 1966 (Solomon 1968). Its overall objectives aim to foster international collaboration in all aspects of biophysics and related areas and to catalyze the advancement of basic biophysical research as well as its many applications. Although IUPAB is active on many fronts, undeniably one of its showcase events is the IUPAB Congress, traditionally organized every three years in different locations worldwide. In 2021, the event was organized and run from Brazil, albeit for the very first time in a virtual format due to travel restrictions imposed by the COVID-19 pandemic. On this occasion, the Congress was organized in conjunction with the annual meetings of both the Brazilian Biophysical Society (SBBf, in its 45th edition) and the Brazilian Society for Biochemistry and Molecular Biology (SBBq, in its 50th edition). Even with the united forces of these well-established local societies, it turned out to be a bumpy ride to bring the event to fruition.Plans for the 20th Congress began in 2016, almost immediately after the decision to hold the event in Brazil, a cause championed by the then-president of the Brazilian Biophysical Society, Marcelo Morales. The original plans had the meeting to be held in the Cidade Maravilhosa (The Wonderful City) of Rio de Janeiro in October 2020. However, it soon became apparent that the political and economic difficulties that the State of Rio was facing at the time meant that it would be wise to search for an alternative venue. The previous experience of SBBq in organizing similar events in the city of Foz do Iguaçu, on the borders with Argentina and Paraguay, made this an obvious choice. Furthermore, the natural attraction of the spectacular Iguaçu waterfalls seemed to be an ideal compensation for Sugar Loaf Mountain, Copacabana beach, and the statue of Christ the Redeemer on Corcovado Mountain.Then came the pandemic. By mid-2020, it had become apparent that there were too many unknowns to make it possible to proceed with an in-person event in October of that year. It was decided to postpone the congress to 2021 but with a firm belief that things would be “back to normal.” Sweet delusion! As 2020 turned into 2021 and the severity and longevity of the pandemic became clearer and clearer (not to mention the abysmal performance of the Brazilian government in failing to rise to the challenge), the inevitable decision was taken to transform the event into an “on-line” congress. This was a first for both the local organizers and the IUPAB.The move to an online format immediately had an impact on the organization of the Young Scientist Program. This was initially envisaged to be a combination of formal and informal activities aimed at uniting about 40 early carrier scientists and post-docs for a couple of days prior to the main event in a stimulating atmosphere conducive to networking. Skillfully conceived, organized, and executed by Eneida de Paula (Campinas) and Eduardo Reis (São Paulo), this too had to be adapted to a “virtual reality.” The successful solution turned out to be a series of fortnightly thematic webinars, including a talk from a recognized authority in the field followed by three or four short presentations from the participants themselves (Table ​(Table1).1). The standard was extremely high and the YSP ended up being a highly effective warm-up to the congress itself. Furthermore, there was excellent geographical diversity among the participants with Europe, Africa, Asia, the Middle East, and both North and South America represented.Table 1Young Scientist Webinar Program