Xian Shu

Bio: Xian Shu is an academic researcher from Chinese Academy of Sciences. The author has contributed to research in topics: Biology & Medicine. The author has an hindex of 1, co-authored 3 publications receiving 7 citations.

A dual-plasmid CRISPR/Cas system for mycotoxin elimination in polykaryotic industrial fungi

Abstract: Mycotoxin contamination causes disease and death in both humans and animals. Monascus Red, produced by Monascus purpureus, is used as a food colorant. However, its application is limited by contami...

The toxin–antitoxin RNA guards of CRISPR-Cas evolved high specificity through repeat degeneration

Abstract: Abstract Recent discovery of ectopic repeats (outside CRISPR arrays) provided unprecedented insights into the nondefense roles of CRISPR-Cas. A striking example is the addiction module CreTA (CRISPR-regulated toxin–antitoxins), where one or two (in most cases) ectopic repeats produce CRISPR-resembling antitoxic (CreA) RNAs that direct the CRISPR effector Cascade to transcriptionally repress a toxic RNA (CreT). Here, we demonstrated that CreTA repeats are extensively degenerated in sequence, with the first repeat (ψR1) being more diverged than the second one (ψR2). As a result, such addiction modules become highly specific to their physically-linked CRISPR-Cas loci, and in most cases, CreA could not harness a heterologous CRISPR-Cas to suppress its cognate toxin. We further disclosed that this specificity primarily derives from the degeneration of ψR1, and could generally be altered by modifying this repeat element. We also showed that the degenerated repeats of CreTA were insusceptible to recombination and thus more stable compared to a typical CRISPR array, which could be exploited to develop highly stable CRISPR-based tools. These data illustrated that repeat degeneration (a common feature of ectopic repeats) improves the stability and specificity of CreTA in protecting CRISPR-Cas, which could have contributed to the widespread occurrence and deep diversification of CRISPR systems.

Associate toxin-antitoxin with CRISPR-Cas to kill multidrug-resistant pathogens

Abstract: CreTA, CRISPR-regulated toxin-antitoxin (TA), safeguards CRISPR-Cas immune systems by inducing cell dormancy/death upon their inactivation. Here, we characterize a bacterial CreTA associating with the I-F CRISPR-Cas in Acinetobacter. CreT is a distinct bactericidal small RNA likely targeting several essential RNA molecules that are required to initiate protein synthesis. CreA guides the CRISPR effector to transcriptionally repress CreT. We further demonstrate a proof-of-concept antimicrobial strategy named ATTACK, which AssociaTes TA and CRISPR-Cas to Kill multidrug resistant (MDR) pathogens. In this design, CRISPR-Cas is programed to target antibiotic resistance gene(s) to selectively kill MDR pathogens or cure their resistance, and when CRISPR-Cas is inactivated or suppressed by unwanted genetic or non-genetic events/factors, CreTA triggers cell death as the last resort. Our data highlight the diversity of RNA toxins coevolving with CRISPR-Cas, and illuminate a combined strategy of CRISPR and TA antimicrobials to 'ATTACK' MDR pathogens.

Novel CRISPR-Cas Systems: An Updated Review of the Current Achievements, Applications, and Future Research Perspectives.

Abstract: According to Darwin’s theory, endless evolution leads to a revolution. One such example is the Clustered Regularly Interspaced Palindromic Repeats (CRISPR)–Cas system, an adaptive immunity system in most archaea and many bacteria. Gene editing technology possesses a crucial potential to dramatically impact miscellaneous areas of life, and CRISPR–Cas represents the most suitable strategy. The system has ignited a revolution in the field of genetic engineering. The ease, precision, affordability of this system is akin to a Midas touch for researchers editing genomes. Undoubtedly, the applications of this system are endless. The CRISPR–Cas system is extensively employed in the treatment of infectious and genetic diseases, in metabolic disorders, in curing cancer, in developing sustainable methods for fuel production and chemicals, in improving the quality and quantity of food crops, and thus in catering to global food demands. Future applications of CRISPR–Cas will provide benefits for everyone and will save countless lives. The technology is evolving rapidly; therefore, an overview of continuous improvement is important. In this review, we aim to elucidate the current state of the CRISPR–Cas revolution in a tailor-made format from its discovery to exciting breakthroughs at the application level and further upcoming trends related to opportunities and challenges including ethical concerns.

Agro-Industrial Residues: Eco-Friendly and Inexpensive Substrates for Microbial Pigments Production

Abstract: Brazilian economy is one of the most important agriculture-based economies in the world, producing coffee, sugarcane, soybean, cassava, fruits and other commodities. This production is responsible for the generation of enormous amounts of daily residues, such as cassava and sugarcane bagasses, rice husk, and coffee peel. These residues are rich sources for renewable energy and can be used as substrates for industrial interest products. Microorganisms are useful biofactories, capable of producing important primary and secondary metabolites, including alcohol, enzymes, antibiotics, pigments, and many other molecules. The production of pigments was reported in bacteria, filamentous fungi, yeasts, and algae. These natural microbial pigments are very promising because synthetic colorants present a long history of allergies and toxicity. In addition, many natural pigments present other biological activities, such as antioxidant and antimicrobial that are interesting for industrial applications. The use of inexpensive substrates for the production of these metabolites is very attractive, considering that agro-industrial residues are generated in high amounts and usually are a problem to the industry. Therefore, in this article we review the production of microbial pigments using agro-industrial residues during this decade (2010-2020), considering both submerged and solid state fermentations, wild-type and genetically modified microorganisms, laboratorial to large-scale bioprocesses, and other possible biological activities related to these pigments.

MrGcn5 is required for the mycotoxin production, sexual and asexual development in Monascus ruber

Abstract: Hongqu is a fermented product of Monascus species, which is widely used as food or food additives in Southeast Asian countries. The contamination of citrinin in Hongqu has caused controversy about its safety. So control of citrinin has always been an important issue of Hongqu products. In current study, we isolated a putative histone acetyltransferase named MrGcn5 and explored its regulatory function on citrinin production. The results showed the citrinin content of MrGcn5 null strain dramatically reduced in the late growth period. Even the citrinin content was as low as 21 % of the wild-type strain, and RT-qPCR experiment suggested that the expression level of genes involving in citrinin synthesis was significantly attenuated in MrGcn5 null strain. With regard to the asexual and sexual development, the conidia germination rate was significantly accelerated in MrGcn5 null strain in the vegetative growth phase, but the number of ascospores was 41.9 % less than the wild-type strain. RT-qPCR revealed the expression level of the homologs to flbA-flbE, fluG and wetA in Aspergillus had changed to some extent in MrGcn5 null strain. Meanwhile, there was no significant effects on the growth, nutrition adaption and Monascus azaphilone pigments production. Taken together, these characteristics of MrGcn5 make it very suitable for targeted improvement to reduce citrinin production in fermentation process.