Proton-transporting and calcium ion-transporting ATPases of Entamoeba histolytica

Genome-wide association study reveals the genetic architecture for calcium accumulation in grains of hexaploid wheat (Triticum aestivum L.)

BACKGROUND

Hexaploid wheat (Triticum aestivum L.) is a leading cereal crop worldwide. Understanding the mechanism of calcium (Ca) accumulation in wheat is important to reduce the risk of human micronutrient deficiencies. However, the mechanisms of Ca accumulation in wheat grain are only partly understood.

RESULTS

Here, a genome-wide association study (GWAS) was performed to dissect the genetic basis of Ca accumulation in wheat grain using an association population consisting of 207 varieties, with phenotypic data from three locations. In total, 11 non-redundant genetic loci associated with Ca concentration were identified and they explained, on average, 9.61-26.93% of the phenotypic variation. Cultivars containing more superior alleles had increased grain Ca concentrations. Notably, four non-redundant loci were mutually verified by different statistical models in at least two environments, indicating their stability across different environments. Four putative candidate genes linked to Ca accumulation were revealed from the stable genetic loci. Among them, two genes, associated with the stable genetic loci on chromosomes 4A (AX-108912427) and 3B (AX-110922471), encode the subunits of V-type Proton ATPase (TraesCS4A02G428900 and TraesCS3B02G241000), which annotated as the typical generators of a proton gradient that might be involved in Ca homeostasis in wheat grain.

CONCLUSION

To identify genetic loci associated with Ca accumulation, we conducted GWAS on Ca concentrations and detected 11 genetic loci; whereas four genetic loci were stable across different environments. A genetic loci hot spot exists at the end of chromosome 4A and associated with the putative candidate gene TraesCS4A02G428900. The candidate gene TraesCS4A02G428900 encodes V-type proton ATPase subunit e and highly expressed in wheat grains, and it possibly involved in Ca accumulation. This study increases our understanding of the genetic architecture of Ca accumulation in wheat grains, which is potentially helpful for wheat Ca biofortification pyramid breeding.

Parasitic protozoa: thiol-based redox metabolism

In a thoughtful and stimulating article, Sylke Müller et al. describe the thiol-based redox metabolism of protozoan parasites and believe that the key enzymes involved in this metabolism have potential use as new drug targets. Additional information on this subject is provided here.

Extracellular matrix-induced signaling in Entamoeba histolytica: its role in invasiveness

Entamoeba histolytica trophozoites can invade the mucosa of the host large intestine to cause disease. Here, Isaura Meza describes recent work indicating that the trophozoites respond to the binding of extracellular matrix proteins by activating receptor-mediated signal transduction pathways. Activation of phosphokinase C or adenylyl cyclase induces protein phosphorylation, actin gene expression and reorganization of the actin cytoskeleton to form adhesive structures that promote interaction with the substrate and the release of proteases. The release of proteases at the sites of contact, with the subsequent degradation of the substrate and generation of chemotactic peptides, facilitates locomotion and dissemination of the invading trophozoites.

Molecular characterization of a sarcoplasmic-endoplasmic reticulum Ca+2 ATPase gene from Trichomonas vaginalis

DNA fragments homologous to P-type cation translocating ATPase genes were identified in Trichomonas vaginalis by polymerase chain reaction (PCR) amplification. The genomic locus corresponding to one PCR fragment, TVCA1, contains a 3,055 base-pair open reading frame encoding a 108,162 dalton protein composed of 981 amino acids. TVCA1 lacks introns, is present in a single copy, and is expressed as a 3.1 kb transcript with short 5' and 3' untranslated regions. Separate primer extension experiments map the 5' end of the TVCA1 transcript to 12 and 16 nucleotide bases (nt) upstream of the methionine initiation codon. The message polyadenylation site is located 62 nt downstream of the protein termination codon at a CA dinucleotide. The TVCA1 protein sequence shares 57-58% similarity with rabbit, schistosome, trypanosome and malarial sarcoplasmic-endoplasmic reticulum calcium (SERCA) pumps, and significantly lower similarity with plasma membrane calcium pumps and cation translocating ATPases of other ion specificities. Structural and functional domains identified in P-type ATPases as well as 61/68 residues specifically implicated in SERCA pump activity are conserved in TVCA1. However, TVCA1 lacks binding sites for phospholamban regulation, thapsigargin inhibition and the calmodulin dependent protein kinase site phosphorylation present in other SERCA pumps.