SHIP2 is a multi-domain inositol 5-phosphatase binding to a variety of phosphotyrosine (pY)-containing proteins through its SH2 domain, so as to regulate various cell signaling pathways by modulating the phosphatidylinositol level in the plasma membrane. Unfavorably, Helicobacter pylori can hijack SHIP2 through the CagA protein to induce gastric cell carcinogenesis. To date, the interaction between SHIP2 and CagA was not analyzed from a structural point of view. Here, the binding of SHIP2-SH2 with Tyr-phosphorylated peptides from four EPIYA motifs (A/B/C/D) in CagA was studied using NMR spectroscopy. The results showed that EPIYA-C and -D bind to a similar interface of SHIP2-SH2, including a pY-binding pocket and a hydrophobic pocket, to achieve high affinity, while EPIYA-A and -B bind to a smaller interface of SHIP2-SH2 with weak affinity. By summarizing the interface and affinity of SHIP2-SH2 for CagA EPIYA-A/B/C/D, c-MET and FcgR2B ITIM, it was proposed that, potentially, SHIP2-SH2 has a selective preference for L > I > V for the aliphatic residues at the pY+3 position in its ligand. This study reveals the rule of the ligand sequence bound by SHIP2-SH2 and the mechanism by which CagA protein hijacks SHIP2, which will help design a peptide inhibitor against SHIP2-SH2.
Yam (Dioscorea spp.) is a multi-species and multi-purpose tuber crop. In this study, the contents of functional components, biological activities, and mineral elements were evaluated in the yam tubers of D. polystachya and D. alata cultivated widely varieties in China. Significant differences in allantoin contents were observed between interspecific and intraspecific yam varieties, and allantoin contents in the four varieties of D. polystachya were significantly higher than those in the D. alata group; however, no significant difference was observed for dioscin levels in all accessions. Furthermore, the phenol and flavonoid contents of D. alata were higher than those of D. polystachya. Protein profiles obtained using nano-liquid chromatography-tandem mass spectrometry (nanoLC-MS) revealed that the levels of proteins related to allantoin, total phenols, and total flavonoids also changed. In addition, both D. polystachya and D. alata tubers contained highly essential minerals, such as high potassium and magnesium, and low heavy metal contents within the specified pollutant content range. This study provides a foundation for the functional food development of Chinese yams and a reference for breeding high-quality yam varieties.
Abstract Purple yam ( Dioscorea alata L.), which is widely distributed in southern China, is characterized by great purple to red flesh or skin, as well as nutritional and medical values. However, their intraspecific genetic diversity remains unknown, which inhibits the germplasm innovation and variety protection of purple yams. In this study, genetic diversity of 26 landraces from southern China were carried out by using 17 morphological traits and 9 simple sequence repeat (SSR) markers, respectively. Results of phenotypic traits showed that all the accessions were divided into four groups at the euclidean distance of 1.43, and there is high correlation between the taxa and the regional distribution of yam accessions. The group IV includes the most accessions mainly from Jiangxi province, followed by group III, which contained accessions mostly from Fujian province. In addition, the leaf shape, leaf vein color and tuber flesh color, displayed higher Shannon's diversity index ( I ) and variation coefficient, which could identify the purple yam resources effectively. Based on the SSR markers analysis, the euclidean distance among all germplasms ranged from 0.17 to 0.79, and the 26 landraces were also clearly separated into four clusters at the euclidean distance of 0.49. Clustering results based on SSR markers and phenotypic traits were consistent roughly. Furthermore, population structure revealed the existence of three sub-populations in all accessions. These results demonstrate the genetic diversity and distinctness among the purple yam from southern China and provide a theoretical basis for the identification and utilization of purple yams.
Water-saving strategies play an important role in improving the resilience of water scarcity in arid and semi-arid areas. This paper has compared the advantages and disadvantages of four kinds of water-saving irrigation methods commonly used in arid/semi-arid areas: rainwater harvesting irrigation, plastic film mulching technology, deficit irrigation, and alternate furrow irrigation. The finding of this study is that biological water-saving which can improve the biological drought tolerance is more cost-effective of further study than the technological water-saving. It can be seen that the latter two (biological water-saving irrigation measures) have lower cost, stronger operability and more promising development prospects. Im addition, future research is suggested to focus more on automatic intelligence to pursue accurate irrigation.
The molecular mechanisms underlying aflatoxin production have been well-studied in strains of the fungus Aspergillus flavus ( A. flavus ) under artificial conditions. However, aflatoxin biosynthesis has rarely been studied in A. flavus strains isolated from field conditions with different aflatoxin-producing ability. In the present study, tandem mass tag (TMT) labeling and high-performance liquid chromatography (HPLC) coupled with tandem-mass spectrometry analysis were used for proteomic quantification in natural isolates of high- and low-aflatoxin-yield A. flavus strains. Additionally, findings obtained using the TMT-labeling method were validated using the high-resolution multiple reaction monitoring (MRM-HR) method. In total, 4,363 proteins were quantified, among which 1,045 proteins were differentially expressed between the high- and low-aflatoxin-yield A. flavus strains. Bioinformatics analysis showed that the up-regulated proteins were significantly enriched in carbon-related metabolism and the biosynthesis of secondary metabolites, whereas the down-regulated proteins were enriched in oxidative phosphorylation. Moreover, GST proteins were found to be significantly down-regulated in high-yield A. flavus strains; this result contradicted previous findings obtained from A. flavus strains grown under artificial conditions. In summary, our study provides novel insights into aflatoxin regulation in A. flavus under field conditions and could facilitate the development of various strategies for the effective control of aflatoxin contamination in food crops.
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.
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