Lysine Succinylation of VBS Contributes to Sclerotia Development and Aflatoxin Biosynthesis in Aspergillus flavus

Aspergillus flavus is a common saprophytic and pathogenic fungus, and its secondary metabolic pathways are one of the most highly characterized owing to its aflatoxin (AF) metabolite affecting global economic crops and human health. Different natural environments can cause significant variations in AF synthesis. Succinylation was recently identified as one of the most critical regulatory post-translational modifications affecting metabolic pathways. It is primarily reported in human cells and bacteria with few studies on fungi. Proteomic quantification of lysine succinylation (Ksuc) exploring its potential involvement in secondary metabolism regulation (including AF production) has not been performed under natural conditions in A. flavus. In this study, a quantification method was performed based on tandem mass tag labeling and antibody-based affinity enrichment of succinylated peptides via high accuracy nano-liquid chromatography with tandem mass spectrometry to explore the succinylation mechanism affecting the pathogenicity of naturally isolated A. flavus strains with varying toxin production. Altogether, 1240 Ksuc sites in 768 proteins were identified with 1103 sites in 685 proteins quantified. Comparing succinylated protein levels between high and low AF-producing A. flavus strains, bioinformatics analysis indicated that most succinylated proteins located in the AF biosynthetic pathway were downregulated, which directly affected AF synthesis. Versicolorin B synthase is a key catalytic enzyme for heterochrome B synthesis during AF synthesis. Site-directed mutagenesis and biochemical studies revealed that versicolorin B synthase succinylation is an important regulatory mechanism affecting sclerotia development and AF biosynthesis in A. flavus. In summary, our quantitative study of the lysine succinylome in high/low AF-producing strains revealed the role of Ksuc in regulating AF biosynthesis. We revealed novel insights into the metabolism of AF biosynthesis using naturally isolated A. flavus strains and identified a rich source of metabolism-related enzymes regulated by succinylation.     

Area and the rapid radiation of Hawaiian Bidens (Asteraceae)

Aim To estimate the rate of adaptive radiation of endemic Hawaiian Bidens and to compare their diversification rates with those of other plants in Hawaii and elsewhere with rapid rates of radiation. Location Hawaii. Methods Fifty‐nine samples representing all 19 Hawaiian species, six Hawaiian subspecies, two Hawaiian hybrids and an additional two Central American and two African Bidens species had their DNA extracted, amplified by polymerase chain reaction and sequenced for four chloroplast and two nuclear loci, resulting in a total of approximately 5400 base pairs per individual. Internal transcribed spacer sequences for additional outgroup taxa, including 13 non‐Hawaiian Bidens, were obtained from GenBank. Phylogenetic relationships were assessed by maximum likelihood and Bayesian inference. The age of the most recent common ancestor and diversification rates of Hawaiian Bidens were estimated using the methods of previously published studies to allow for direct comparison with other studies. Calculations were made on a per‐unit‐area basis. Results We estimate the age of the Hawaiian clade to be 1.3–3.1 million years old, with an estimated diversification rate of 0.3–2.3 species/million years and 4.8 × 10^?5 to 1.3 × 10^?4 species Myr^?1 km^?2. Bidens species are found in Europe, Africa, Asia and North and South America, but the Hawaiian species have greater diversity of growth form, floral morphology, dispersal mode and habitat type than observed in the rest of the genus world‐wide. Despite this diversity, we found little genetic differentiation among the Hawaiian species. This is similar to the results from other molecular studies on Hawaiian plant taxa, including others with great morphological variability (e.g. silverswords, lobeliads and mints). Main conclusions On a per‐unit‐area basis, Hawaiian Bidens have among the highest rates of speciation for plant radiations documented to date. The rapid diversification within such a small area was probably facilitated by the habitat diversity of the Hawaiian Islands and the adaptive loss of dispersal potential. Our findings point to the need to consider the spatial context of diversification – specifically, the relative scale of habitable area, environmental heterogeneity and dispersal ability – to understand the rate and extent of adaptive radiation.     

In-depth Profiling and Quantification of the Lysine Acetylome in Hepatocellular Carcinoma with a Trapped Ion Mobility Mass Spectrometer

Hepatocellular carcinoma (HCC) is the third most common cause of cancer-related death worldwide with limited therapeutic options. Comprehensive investigation of protein posttranslational modifications in HCC is still limited. Lysine acetylation is one of the most common types of posttranslational modification involved in many cellular processes and plays crucial roles in the regulation of cancer. In this study, we analyzed the proteome and K-acetylome in eight pairs of HCC tumors and normal adjacent tissues using a timsTOF Pro instrument. As a result, we identified 9219 K-acetylation sites in 2625 proteins, of which 1003 sites exhibited differential acetylation levels between tumors and normal adjacent tissues. Interestingly, many novel tumor-specific K-acetylation sites were characterized, for example, filamin A (K865), filamin B (K697), and cofilin (K19), suggesting altered activities of these cytoskeleton-modulating molecules, which may contribute to tumor metastasis. In addition, we observed an overall suppression of protein K-acetylation in HCC tumors, especially for enzymes from various metabolic pathways, for example, glycolysis, tricarboxylic acid cycle, and fatty acid metabolism. Moreover, the expression of deacetylase sirtuin 2 (SIRT2) was upregulated in HCC tumors, and its role of deacetylation in HCC cells was further explored by examining the impact of SIRT2 overexpression on the proteome and K-acetylome in Huh7 HCC cells. SIRT2 overexpression reduced K-acetylation of proteins involved in a wide range of cellular processes, including energy metabolism. Furthermore, cellular assays showed that overexpression of SIRT2 in HCC cells inhibited both glycolysis and oxidative phosphorylation. Taken together, our findings provide valuable information to better understand the roles of K-acetylation in HCC and to treat this disease by correcting the aberrant acetylation patterns.     

Efficient synthesis of novel glutamate homologues and investigation of their affinity and selectivity profile at ionotropic glutamate receptors

A convenient synthesis of four new enantiomerically pure acidic amino acids is reported and their affinity at ionotropic glutamate receptors was determined. The new compounds are higher homologues of glutamic acid in which the molecular complexity has been increased by introducing an aromatic/heteroaromatic ring, that is a phenyl or a thiophene ring, that could give additional electronic interactions with the receptors. The results of the present investigation indicate that the insertion of an aromatic/heteroaromatic ring into the amino acid skeleton of glutamate higher homologues is well tolerated and this modification could be exploited to generate a new class of NMDA antagonists.     

Biology and host preference of Selitrichodes neseri: A potential biological control agent of the Eucalyptus gall wasp,Leptocybe invasa

Selitrichodes neseri (Hymenoptera: Eulophidae) is a parasitoid of the invasive gall-forming wasp Leptocybe invasa (Hymenoptera: Eulophidae), which has caused serious damage to Eucalyptus plantations in many parts of the world. S. neseri is a recently discovered parasitoid considered to be a potentially important biological control agent of L. invasa. The aim of this study was to provide the first basic data on the biology of S. neseri, which is essential for its application in biological control. S. neseri was shown to be a biparental ectoparasitoid. Observation from dissected galls indicated that the parasitoid developed on late larvae, pupae and callow adults, although development did occur in a range of gall ages. Observed nominal parasitism in captivity ranged from 9.7% to 71.8%. Adult S. neseri specimens, fed with honey-water and galled Eucalyptus leaves, survived an average of 26 days at 26 °C. The average developmental time from oviposition to emergence was 19.3 days ± 0.2 days. There was no pre-oviposition period. A single female produced a maximum of thirty-nine offspring, with a maximum of ten per day. Dissection of the ovaries showed that twelve ovarioles were present. The sex ratio of S. neseri observed in this study was 1:3.43 males:females. Galls of native insects most closely related to L. invasa and to galls of similar morphology to L. invasa-induced galls, were not suitable for S. neseri oviposition. S. neseri showed considerable potential as a biological control agent of L. invasa due to its relatively short developmental time, long adult life span when supplemented with carbohydrates, ability to utilize a range of gall ages and the fact that it has a high level of host specificity.     

A histological and morphometric study on the tissue and cellular distribution of iron in carp Cyprinus carpio L. during chronic waterborne exposure

The effect of long-term (77 day) exposure of carp Cyprinus carpio to low concentrations of waterborne iron (1 mg Fe-dextran l⁻¹) on accumulation and cellular distribution of iron in the liver was assessed using Perl's staining and histological observations and morphometric measurements. Accumulation of iron in the liver occurred after 14 days of exposure, when the majority of the iron was found in the sinusoidal endothelium with lower amounts in the cytoplasm and nuclei of hepatocytes. Upon further treatment the iron was predominantly distributed in the cytoplasm of the hepatocytes either as granules or diffusive iron and in macrophages.