Deciphering proteolytic processing of carbonic anhydrase 1 from Chlamydomonas reinhardtii

A Chlamydomonas gene CAH1 is responsible for the expression of the secreted protein periplasmic Carbonic Anhydrase 1 (CAH1), which undergoes unique post-translational processing. The pre-protein that has endomembrane targeting sequence and one large and one small subunit separated by a small 35 amino acid stretch called as spacer, undergoes proteolytic processing that cleaves off the targeting sequence and the spacer, giving rise to a mature, glycosylated CAH1 protein. This hetero-tetramer consists of two large and two small subunits attached to each other by disulphide bridges. This research work involves the analysis of the intrinsic factors of the pre-protein that are essential for the proteolytic cleavage of the spacer from the pre-protein. Various potential target sites for the proteases, in and around the spacer region for the proteolytic cleavage were investigated by generating transgenic Arabidopsis plants expressing mutated forms of CAH1 gene. Failure to locate any amino acid sequence/s inside or around the spacer region that controls proteolysis suggests that the proteolysis of the pre-protein is largely independent of the sequence of amino acid residues separating large and small subunits which was supported by successful demonstration of proteolysis of the constructs with the spacer with reverse order of amino acid residues and the spacer with radically different amino acid sequence, in transgenic Arabidopsis plants. We predict possible involvement of more than one protease that act on more than one target sequence in and/or around the spacer region. Analysis of the constructs with progressively reducing number of amino acid residues between the disulfide bond forming cystine residues of large and small subunit suggests that the proteolytic cleavage may be dependent more on the number and the composition of the amino acids between the two cystine residues that form a disulfide bridge between large and small subunits, than the actual sequence. Most interestingly the successful proteolysis of the CAH1 construct lacking previously demonstrated spacer region questions the very requirement of the spacer for the proteolysis of the pre-protein. Even though more research is required to understand this processing better, the post-translational processing undergone by CAH1 may utilize a mechanism that is conserved across the diverse kingdoms making it an interesting and important process to study

“Cyst-ained” research into Heterodera parasitism

Nematodes are roundworms that constitute the phylum Nematoda. Only a small fraction of nematode genera contains plant-parasitic or animal-parasitic species, while the majority of nematodes are free-living [1]. Heterodera glycines, the soybean cyst nematode, is a plant-parasitic nematode causing major damage to soybean production worldwide. Annual United States yield loss estimates due to H. glycines range up to $1.2 billion, likely making this nematode the most serious pathogen threat to sustainable soybean production [2]. While cyst nematode-resistant soybean cultivars are available, they do not control all H. glycines biotypes present in a given field and, therefore, select for virulent nematode populations that can overcome available resistance genes, leading to a slow but steady erosion of resistance efficacy [3]. Clearly, long-term management of the soybean cyst nematode in modern soybean production will need additional tools, and it is likely that such new tools will be developed from detailed molecular knowledge of the complex Heterodera cyst nematode-plant interactions. This short review provides a snapshot of currently unfolding research discoveries from the genus Heterodera, which also includes other cyst nematodes, particularly the sugar beet cyst nematode H. schachtii, which can infect Arabidopsis and therefore has been used as a model system. Since nematode effectors (the proteins delivered into host plant tissues to mediate parasitism) are at the forefront of nematode–plant interactions, their identification and functional characterization are heavily emphasized in this manuscript

SCNBase: a genomics portal for the soybean cyst nematode (Heterodera glycines)

Soybean is an important worldwide crop, and farmers continue to experience significant yield loss due to the soybean cyst nematode (SCN), Heterodera glycines. This soil-borne roundworm parasite is rated the most important pathogen problem in soybean production. The infective nematodes enter into complex interactions with their host plant by inducing the development of specialized plant feeding cells that provide the parasites with nourishment. Addressing the SCN problem will require the development of genomic resources and a global collaboration of scientists to analyze and use these resources. SCNBase.org was designed as a collaborative hub for the SCN genome. All data and analyses are downloadable and can be analyzed with three integrated genomic tools: JBrowse, Feature Search and BLAST. At the time of this writing, a number of genomic and transcriptomic data sets are already available, with 43 JBrowse tracks and 21 category pages describing SCN genomic analyses on gene predictions, transcriptome and read alignments, effector-like genes, expansion and contraction of genomic repeats, orthology and synteny with related nematode species, Single Nucleotide Polymorphism (SNPs) from 15 SCN populations and novel splice sites. Standard functional gene annotations were supplemented with orthologous gene annotations using a comparison to nine related plant-parasitic nematodes, thereby enabling functional annotations for 85% of genes. These annotations led to a greater grasp on the SCN effectorome, which include over 3324 putative effector genes. By designing SCNBase as a hub, future research findings and genomic resources can easily be uploaded and made available for use by others with minimal needs for further curation. By providing these resources to nematode research community, scientists will be empowered to develop novel, more effective SCN management tools.This is the version of record for the article Masonbrink, Rick, Tom R. Maier, Arun S. Seetharam, Parijat S. Juvale, Levi Baber, Thomas J. Baum, and Andrew J. Severin. "SCNBase: a genomics portal for the soybean cyst nematode (Heterodera glycines)." Database 2019 (2019). Available online at DOI: 10.1093/database/baz111. Copyright 2019 The Author(s). Attribution 4.0 International (CC BY 4.0). Posted with permission