Genetic diversity of Fusarium pseudocircinatum in the central western region of Mexico: the case of big-leaf mahogany malformation disease

Fusarium pseudocircinatum is the main causal agent of big-leaf mahogany malformation disease (BLMMD) of mahogany (Swietenia macrophylla) in Mexico. Although, BLMMD is the most important disease for this high-value timber species, there is a lack of information on the genetic variation present in geographically diverse isolates of F. pseudocircinatum. The objective of this study was to determine the genetic diversity of populations of F. pseudocircinatum causing BLMMD in the central western region of Mexico. A total of 611 big-leaf mahogany trees were inspected at eight sites in four states (Colima, Guerrero, Jalisco and Michoacán); of these, 42.7% showed malformation symptoms similar to those of BLMMD. Of 374 Fusarium isolates that were recovered, 277 were identified as F. pseudocircinatum, 56 were F. mexicanum, and 41 were Fusarium spp. An ISSR analysis of the F. pseudocircinatum isolates generated 51 bands of which 38 were polymorphic (76.8%) with a mean of 17 bands per primer. A total of 87 multilocus genotypes (MLGs) were identified. Nei’s genetic diversity analysis showed that the isolates had a high genetic diversity average (0.147), with values ranging from 0.070 to 0.365 depending of the geographical location. An analysis of molecular variance revealed that the variation within the populations was low (27.36%), while the variation within MLGs was significant (72.64%), indicating genetic flow. Overall, the genetic variability of F. pseudocircinatum populations was high and the MLGs from Colima (Colima) and Gabriel Zamora (Michoacán) were placed centrally, which possibly is evidence of ancestry and indicates its dispersion routes in the central western region of Mexico.

     

The PhoP/PhoQ system and its role in Serratia marcescens pathogenesis

Serratia marcescens is able to invade, persist, and multiply inside nonphagocytic cells, residing in nonacidic, nondegradative, autophagosome-like vacuoles. In this work, we have examined the physiological role of the PhoP/PhoQ system and its function in the control of critical virulence phenotypes in S. marcescens. We have demonstrated the involvement of the PhoP/PhoQ system in the adaptation of this bacterium to growth on scarce environmental Mg(2+), at acidic pH, and in the presence of polymyxin B. We have also shown that these environmental conditions constitute signals that activate the PhoP/PhoQ system. We have found that the two S. marcescens mgtE orthologs present a conserved PhoP-binding motif and demonstrated that mgtE1 expression is PhoP dependent, reinforcing the importance of PhoP control in magnesium homeostasis. Finally, we have demonstrated that phoP expression is activated intracellularly and that a phoP mutant strain is defective in survival inside epithelial cells. We have shown that the Serratia PhoP/PhoQ system is involved in prevention of the delivery to degradative/acidic compartments.     

Scale‐Dependent Spatial Match between Fruits and Fruit‐eating Birds during the Breeding Season in Yungas Andean Forests

The multi‐scale spatial match between bird and food abundances is a main driver of the structure of fruit‐eating bird assemblages. We explored how the activity of fruit‐eating birds was influenced by the abundance of fruits at the local and landscape scales in Andean mountain forests during the breeding season, when most birds forage close to their nest. We measured: (1) the spatial scale of variation in the abundance of fruits, (2) the spatial scale of variation in the activity of fruit‐eating birds, and (3) the spatial match between both variables. The sampling design consisted of eleven 1.2‐ha sites, each subdivided into 30 cells of 20 × 20 m, where we sampled fruits and fruit‐eating birds. We found that fruit consumption, and to a lesser extent bird abundance, were associated with local spatial variation in abundance of selected fruit species. However, fruit‐eating birds did not modify their spatial distribution in the landscape following changes in availability of these fruits. Our study shows that fruit‐eating birds detect local spatial variation in fruit availability in their home breeding ranges, and exploit patches with large clusters of selected fruits. However, it may be unprofitable for breeding birds to stray too far from their nests to exploit fruit‐rich patches, accounting for the absence of fruit tracking at larger spatial scales.     

Roles of glycosylation on the antifungal activity and apoplast accumulation of StAPs (Solanum tuberosum aspartic proteases)

Specific roles of glycosylation appear to be protein-dependent. Plant aspartic proteases (APs) contain two or more consensus N-glycosylation sites; however, the importance of them is not well understood. StAPs (Solanum tuberosum aspartic proteases) are bifunctional proteins with both proteolytic and antimicrobial activities. These proteins are accumulated into the intercellular washing fluid of potato tubers and leaves after wounding or infection. In this paper we investigated the importance of glycosylation on the StAPs apoplast accumulation, biochemical parameters, and fungicidal activity. Assays to evaluate the importance of StAPs glycosylation groups by using glycosylation inhibitors demonstrate that carbohydrate portions are essential to StAPs accumulation into the apoplast of tubers and leaves after wounding or detachment, respectively. Bifunctional activity of StAPs is differentially affected by this post-translational modification. Results obtained show that not significant changes were produced in the physicochemical properties after StAPs deglycosylation (pH and thermal-optimum activity and index of protein surface hydrophobicity). Otherwise, StAPs antifungal activity is affected by deglycosylation. Deglycosylated StAPs (dgStAPs) fungicidal activity is lower than native StAPs at all concentrations and times assayed. In summary, glycosylation has not a significant role on the StAPs conformational structure. However, it is involved in the StAPs subcellular accumulation and antifungal activity suggesting that it could be necessary for StAPs membrane and/or protein interactions and subsequently its biological function(s).     

Impaired sperm fertilizing ability in mice lacking Cysteine-RIch Secretory Protein 1 (CRISP1)

Mammalian fertilization is a complex multi-step process mediated by different molecules present on both gametes. Epididymal protein CRISP1, a member of the Cysteine-RIch Secretory Protein (CRISP) family, was identified by our laboratory and postulated to participate in both sperm–zona pellucida (ZP) interaction and gamete fusion by binding to egg-complementary sites. To elucidate the functional role of CRISP1 in vivo, we disrupted the Crisp1 gene and evaluated the effect on animal fertility and several sperm parameters. Male and female Crisp1^−/− animals exhibited no differences in fertility compared to controls. Sperm motility and the ability to undergo a spontaneous or progesterone-induced acrosome reaction were neither affected in Crisp1^−/− mice. However, the level of protein tyrosine phosphorylation during capacitation was clearly lower in mutant sperm than in controls. In vitro fertilization assays showed that Crisp1^−/− sperm also exhibited a significantly reduced ability to penetrate both ZP-intact and ZP-free eggs. Moreover, when ZP-free eggs were simultaneously inseminated with Crisp1^+/+ and Crisp1^−/− sperm in a competition assay, the mutant sperm exhibited a greater disadvantage in their fusion ability. Finally, the finding that the fusion ability of Crisp1^−/− sperm was further inhibited by the presence of CRISP1 or CRISP2 during gamete co-incubation, supports that another CRISP cooperates with CRISP1 during fertilization and might compensate for its lack in the mutant mice. Together, these results indicate that CRISP proteins are players in the mammalian fertilization process. To our knowledge this is the first knockout mice generated for a CRISP protein. The information obtained might have important functional implications for other members of the widely distributed and evolutionarily conserved CRISP family.     

Occupancy models including local and landscape variables are useful to assess the distribution of a salamander species at risk

Numerous amphibian species are at risk of extinction worldwide. Therefore, reliable estimations of the distribution and abundance of these species are necessary for their conservation. Generally, amphibians are difficult to detect in the wild, which compromises the accuracy of long-term population monitoring and management. Occupancy models are useful tools to assess how environmental variables, at a local and at a landscape scale, affect the distribution and abundance of organisms taking into account species imperfect detectability. In this study, we evaluated with an environmental multiscale approach the seasonal variation of the occupation area of the threatened salamander, Ambystoma ordinarium along its distribution range. We obtained readings in 60 streams of physicochemical variables associated with habitat quality and landscape features. We found that detection and occupation probability of A. ordinarium are seasonally associated with different environmental variables. During the dry season, detectability was positively associated with temperature and stream depth, whereas occupancy was positively associated with the proportion of crops in the landscape and stream elevation. In the rainy season, the detection probability was not explained by any variable considered, and occupancy was negatively associated with stream's electrical conductivity and dissolved oxygen. Based on the estimation of occupied sites, we showed that A. ordinarium presents a more restricted distribution range than previously projected. Therefore, our results reveal the importance of evaluating the accuracy of distribution estimates for the conservation of threatened species as A. ordinarium.     

Microbial Hydrolysis of Acetylated Nucleosides

Enzymatic hydrolysis of acetylated nucleosides using microbial whole cells has been carried out for the first time. Unlike Candida antarctica B lipase-catalysed alcoholysis, none of the tested microorganisms displayed a common deacetylation profile. Depending on the substrate and the biocatalyst used, 5′-selective deprotection or mixtures of mono O-acetylated products were obtained.     

Seasonal differences in rainfall,food availability,and the foraging behavior of Tropical Kingbirds in the southern Amazon Basin

ABSTRACT Little is known about the relationship between seasonal food availability and the foraging strategies of insectivorous Neotropical birds. We studied a population of Tropical Kingbirds (Tyrannus melancholicus), a primarily insectivorous species, in eastern Bolivia to examine relationships between rainfall, food availability, and foraging strategies throughout the year. Our study site in the southern Amazon Basin was characterized by strong seasonal variation in the abundance of the kingbird's main insect prey (coleopterans and hymenopterans), with reduced abundance during the nonbreeding season which largely overlaps the dry season. Overall, mean search times for insect prey by Tropical Kingbirds during the breeding (96.9 ± 85.6 [SD] sec) and nonbreeding (83.7 ± 91.2 sec) seasons did not differ (P= 0.23). However, during the nonbreeding season, kingbird search times were negatively, but nonsignificantly, correlated with coleopteran abundance (r²= 0.43, P= 0.16) and significantly and negatively correlated with hymenopteran abundance (r²= 0.72, P= 0.03). Although insect abundance differed seasonally, kingbird search times did not, perhaps because kingbirds forage on a greater variety of insects during the nonbreeding season or, during the breeding season, kingbird search times may be influenced by the need to monitor and defend nests as well as constraints on the types of prey that can be fed to nestlings. However, the reduced abundance of their primary insect prey and negative relationships between the abundance of those prey and search times during the dry, nonbreeding season suggest that Tropical Kingbirds in southern Amazonia may be food limited, potentially explaining why some migrate and spend that season elsewhere.