Distribution of stem-end rot on the canopy in ‘Hass’ avocado trees in two coastal areas in Peru

Stem-end rot (SER) of avocado is caused by several fungal species, and it is presented worldwide. This plant disease currently affects several avocado producer regions in Peru, causing fruit rot, impacting the industry negatively. Research about SER distribution in the canopy of avocado trees is limited. Thus, the present study aimed to compare which areas in the canopy are prone to have more SER in ‘Hass’ avocado harvested fruit in two different coastal areas in Peru. The experiment was conducted in the northern (Barranca) and southern (Cañete) of Lima. ‘Hass’Avocado fruits from both producer areas were collected to identify the causal agent; Lasiodiplodia theobromae was isolated from infected fruits. Identification was conducted based on morphological features and a partial DNA sequence of the translation elongation factor 1-α gene (tef1-α). The results showed that fruits inside the tree canopy were prone to have a higher disease incidence than the fruits located in the external site (P<0.001). Besides, internal-site fruits displayed a higher percentage of infected fruit for each grade disease (P<0.001) than external-site fruits, except for grade 0 (fruits without symptoms) and grade 1. Finally, the results suggested that the altitude where the fruit is positioned on the canopy could influence the incidence of SER, where fruits located in the high part revealed less incidence than the low section. The results are valuable for enhancing management strategies and avoiding postharvest loss of avocado fruits in our region.

Low-Valent Tungsten Redox Catalysis Enables Controlled Isomerization and Carbonylative Functionalization of Alkenes

Tungsten catalysis has played an instrumental role in the history of organometallic chemistry, with electrophilic, fully oxidized W(VI) catalysts featuring prominently in olefin polymerization and metathesis reactions. Here, we report that the simple W(0) precatalyst, W(CO)₆, catalyzes the isomerization and hydrocarbonylation of alkenes via a W(0)/W(II) redox couple. The 6- to 7-coordinate geometry changes associated with this redox process are key in allowing isomerization to take place over multiple positions and stop at a defined unactivated internal site that is primed for <i>in situ</i> functionalization. DFT studies and crystallographic characterization of multiple directing-group-bound W(II) model complexes illuminate potential intermediates of this redox cycle and showcase the capabilities of the 7-coordinate W(II) geometry to facilitate challenging alkene functionalizations.

Low-Valent Tungsten Redox Catalysis Enables Controlled Isomerization and Carbonylative Functionalization of Alkenes

Tungsten catalysis has played an instrumental role in the history of organometallic chemistry, with electrophilic, fully oxidized W(VI) catalysts featuring prominently in olefin polymerization and metathesis reactions. Here, we report that the simple W(0) precatalyst, W(CO)₆, catalyzes the isomerization and hydrocarbonylation of alkenes via a W(0)/W(II) redox couple. The 6- to 7-coordinate geometry changes associated with this redox process are key in allowing isomerization to take place over multiple positions and stop at a defined unactivated internal site that is primed for <i>in situ</i> functionalization. DFT studies and crystallographic characterization of multiple directing-group-bound W(II) model complexes illuminate potential intermediates of this redox cycle and showcase the capabilities of the 7-coordinate W(II) geometry to facilitate challenging alkene functionalizations.

Protein dosage of the lldPRD operon is correlated with RNase E-dependent mRNA processing.

The ability of Escherichia coli to grow on L-lactate as a sole carbon source depends on the expression of the lldPRD operon. A striking feature of this operon is that the transcriptional regulator (LldR) encoding gene is located between the permease (LldP) and the dehydrogenase (LldD) encoding genes. In this study we report that dosage of the LldP, LldR, and LldD proteins is not modulated on the transcriptional level. Instead, modulation of protein dosage is primarily correlated with RNase E-dependent mRNA processing events that take place within the lldR mRNA, leading to the immediate inactivation of lldR, to differential segmental stabilities of the resulting cleavage products, and to differences in the translation efficiencies of the three cistrons. A model for the processing events controlling the molar quantities of the proteins in the lldPRD operon is presented and discussed. Importance Adjustment of gene expression is critical for proper cell function. For the case of polycistronic transcripts, posttranscriptional regulatory mechanisms can be used to fine-tune the expression of individual cistrons. Here, we elucidate how protein dosage of the Escherichia coli lldPRD operon, which presents the paradox of having the gene encoding a regulator protein located between genes that code for a permease and an enzyme, is regulated. Our results demonstrate that the key event in this regulatory mechanism involves the RNase E-dependent cleavage of the primary lldPRD transcript at internal site(s) located within the lldR cistron, resulting in a drastic decrease of intact lldR mRNA, to differential segmental stabilities of the resulting cleavage products, and to differences in the translation efficiencies of the three cistrons.

ATP modulates SLC7A5 (LAT1) synergistically with cholesterol

The plasma membrane transporter hLAT1 is responsible for providing cells with essential amino acids. hLAT1 is over-expressed in virtually all human cancers making the protein a hot-spot in the fields of cancer and pharmacology research. However, regulatory aspects of hLAT1 biology are still poorly understood. A remarkable stimulation of transport activity was observed in the presence of physiological levels of cholesterol together with a selective increase of the affinity for the substrate on the internal site, suggesting a stabilization of the inward open conformation of hLAT1. A synergistic effect by ATP was also observed only in the presence of cholesterol. The same phenomenon was detected with the native protein. Altogether, the biochemical assays suggested that cholesterol and ATP binding sites are close to each other. The computational analysis identified two neighboring regions, one hydrophobic and one hydrophilic, to which cholesterol and ATP were docked, respectively. The computational data predicted interaction of the ϒ-phosphate of ATP with Lys 204, which was confirmed by site-directed mutagenesis. The hLAT1-K204Q mutant showed an impaired function and response to ATP. Interestingly, this residue is conserved in several members of the SLC7 family.

More than just a ticket canceller: The mitochondrial processing peptidase matures complex precursor proteins at internal cleavage sites

Most mitochondrial proteins are synthesized in the cytosol as precursors that carry N-terminal presequences. After import into mitochondria, these targeting signals are cleaved off by the mitochondrial processing peptidase MPP, giving rise to shorter mature proteins. Using the mitochondrial tandem protein Arg5,6 as a model substrate, we demonstrate that MPP has an additional role in preprotein maturation, beyond the removal of presequences. Arg5,6 is synthesized as a polyprotein precursor that is imported into the mitochondrial matrix and subsequently separated into two distinct enzymes that function in arginine biogenesis. This internal processing is performed by MPP, which cleaves the Arg5,6 precursor both at its N-terminus and at an internal site between the Arg5 and Arg6 parts. The peculiar organization and biogenesis of Arg5,6 is conserved across fungi and might preserve the mode of co-translational subunit association of the arginine biosynthesis complex of the polycistronic arginine operon in prokaryotic mitochondrial ancestors. Putative MPP cleavage sites are also present at the junctions in other mitochondrial fusion proteins from fungi, plants and animals. Our data suggest that, in addition to its role as “ticket canceller” for the removal of presequences, MPP exhibits a second, widely conserved activity as internal processing peptidase for complex mitochondrial precursor proteins.

Reconstructing the complex evolutionary history of the fused Aco2 gene in fission yeast

The Aco2 gene of Schizosaccharomyces pombe was formed by gene fusion between curious partners, namely genes encoding the enzyme aconitase and a mitochondrial ribosomal protein. In addition to a full-length transcript, a truncated mRNA encoding only the N-terminal aconitase domain is produced by polyadenylation at an internal site. Protein products of the gene are found in the nucleus, mitochondria and cytoplasm, consistent with the presence of multiple subcellular targeting signals. To reconstruct the evolution of this complex gene, we studied homologous genes from a range of related species. We find evidence for a dynamic history within Taphrinomycotina, including: early evolution of a nuclear localization signal; creation of a 3’ intron that could be involved in regulating subcellular targeting; evolution of multiple peroxisomal targeting signals in different lineages; and recurrent gene loss. We present a likely stepwise model for the evolution of this remarkable gene and discuss alternative scenarios.

Coleoptera in the Canopy of the Cloud Forest From Tlanchinol in the State of Hidalgo, Mexico

We describe the biodiversity, seasonal variation, and the possible edge effect of Coleoptera found in the canopy of the cloud forest in Tlanchinol in the state of Hidalgo. The coleopterans were collected by means of three fogging events during the dry season and another three during the rainy season in three sites of the forest: the edge, an intermediate, and an internal site. In total, 3,487 coleopterans were collected, belonging to 325 morphospecies from 52 families. The family with the largest number of morphospecies and abundance was Staphylinidae, followed by Curculionidae and Chrysomelidae. Species richness and abundance were higher in the dry season than in the rainy season. The biodiversity analyses, however, suggest that the rainy season showed the highest biodiversity levels, mainly because of the pronounced dominance of some species in the dry season. Species composition was different between the dry and rainy seasons. The internal site showed the lowest biodiversity compared with the intermediate and edge sites. The main edge effect detected was that species composition in the edge site differed from the intermediate and internal sites. Species composition did not differ significantly between the two latter sites. These results suggest that the study zone had a considerable level of biodiversity of Coleoptera and that it was very likely in a well-preserved condition, which supports the findings of another study previously performed in the same site using flight intercept traps.

Minute Virus of Canines NP1 Protein Interacts with the Cellular Factor CPSF6 To Regulate Viral Alternative RNA Processing

ABSTRACTThe NP1 protein of minute virus of canines (MVC) governs production of the viral capsid proteins via its role in pre-mRNA processing. NP1 suppresses polyadenylation and cleavage at its internal site, termed the proximal polyadenylation (pA)p site, to allow accumulation of RNAs that extend into the capsid gene, and it enhances splicing of the upstream adjacent third intron, which is necessary to properly enter the capsid protein open reading frame. We find the (pA)p region to be complex. It contains redundant classicalcis-acting signals necessary for the cleavage and polyadenylation reaction and splicing of the adjacent upstream third intron, as well as regions outside the classical motifs that are necessary for responding to NP1. NP1, but not processing mutants of NP1, bound to MVC RNA directly. The cellular RNA processing factor CPSF6 interacted with NP1 in transfected cells and participated with NP1 to modulate its effects. These experiments further characterize the role of NP1 in parvovirus gene expression.IMPORTANCETheParvovirinaeare small nonenveloped icosahedral viruses that are important pathogens in many animal species, including humans. Unlike other parvoviruses, the bocavirus genus controls expression of its capsid proteins via alternative RNA processing, by both suppressing polyadenylation at an internal site, termed the proximal polyadenylation (pA)p site, and by facilitating splicing of an upstream adjacent intron. This regulation is mediated by a small genus-specific protein, NP1. Understanding thecis-acting targets of NP1, as well as the cellular factors with which it interacts, is necessary to more clearly understand this unique mode of parvovirus gene expression.