An effector ofPuccinia striiformisf. sp.triticitargets chloroplasts with a novel and robust targeting signal

Fungal pathogens secrete effector molecules into host plant cells to suppress host immunity to colonize plants. Ongoing efforts are being made to identify and characterize effector proteins in many fungal plant pathogens. Nevertheless, the precise biological and biochemical functions of many effectors, such as their trafficking from the pathogen to the host, have yet to be fully understood. In this study, we show that an effector candidate, matured PstCTE1 ofPuccinia striiformisf. sp.tritici, localizes to chloroplasts when expressed inplanta. It has no conserved transit signal region that can be detected by widely accepted prediction tools including TargetP and ChloroP, it must be carrying a unique localization signal. We have shown that N-terminal tagged red fluorescent protein has no effect on the chloroplast localization of PstCTE1, suggesting a new chloroplast translocation mechanism. We also observed the entrance of the candidate effector to the chloroplast even with the construct having the intact signal peptide on the N-terminus of the transit peptide region. Possibly due to overexpression of the protein inN. benthamina, accumulation in the ER (cytoplasm) was obvious. As previously reported, PstCTE1, similar to effector proteins, may either escape from the secretory pathway by retrograde transport, or translation may occur at alternative sites. This would result in a truncated and/or non-functional signal peptide at the N-terminus in a non-host model system (Nicotiana benthamiana), if it is not re-entering the cell from the apoplast. Our study adds PstCTE1 to the pool of few candidate effectors, experimentally shown to target the chloroplast

In-depth secretome analysis of Puccinia striiformis f. sp. tritici in infected wheat uncovers effector functions

The importance of wheat yellow rust disease, caused by Puccinia striiformis f. sp. tritici (Pst), has increased substantially due to the emergence of aggressive new Pst races in the last couple of decades. In an era of escalating human populations and climate change, it is vital to understand the infection mechanism of Pst in order to develop better strategies to combat wheat yellow disease. The present study focuses on the identification of small secreted proteins (SSPs) and candidate-secreted effector proteins (CSEPs) that are used by the pathogen to support infection and control disease development. We generated de novo assembled transcriptomes of Pst collected from wheat fields in central Anatolia. We inoculated both susceptible and resistant seedlings with Pst and analyzed haustoria formation. At 10 days post-inoculation (dpi), we analyzed the transcriptomes and identified 10550 Differentially Expressed Unigenes (DEGs), of which 6072 were Pst-mapped. Among those Pst-related genes, 227 were predicted as PstSSPs. In silico characterization was performed using an approach combining the transcriptomic data and datamining results to provide a reliable list to narrow down the ever-expanding repertoire of predicted effectorome. The comprehensive analysis detected 14 Differentially Expressed Small-Secreted Proteins (DESSPs) that overlapped with the genes in available literature data to serve as the best CSEPs for experimental validation. One of the CSEPs was cloned and studied to test the reliability of the presented data. Biological assays show that the randomly selected CSEP, Unigene17495 (PSTG 10917), localizes in the chloroplast and is able to suppress cell death induced by INF1 in a Nicotiana benthamiana heterologous expression system

Table_1_Puccinia striiformis f. sp. tritici effectors in wheat immune responses.docx

The obligate biotrophic fungus Puccinia striiformis f. sp. tritici, which causes yellow (stripe) rust disease, is among the leading biological agents resulting in tremendous yield losses on global wheat productions per annum. The combatting strategies include, but are not limited to, fungicide applications and the development of resistant cultivars. However, evolutionary pressure drives rapid changes, especially in its “effectorome” repertoire, thus allowing pathogens to evade and breach resistance. The extracellular and intracellular effectors, predominantly secreted proteins, are tactical arsenals aiming for many defense processes of plants. Hence, the identity of the effectors and the molecular mechanisms of the interactions between the effectors and the plant immune system have long been targeted in research. The obligate biotrophic nature of P. striiformis f. sp. tritici and the challenging nature of its host, the wheat, impede research on this topic. Next-generation sequencing and novel prediction algorithms in bioinformatics, which are accompanied by in vitro and in vivo validation approaches, offer a speedy pace for the discovery of new effectors and investigations of their biological functions. Here, we briefly review recent findings exploring the roles of P. striiformis f. sp. tritici effectors together with their cellular/subcellular localizations, host responses, and interactors. The current status and the challenges will be discussed. We hope that the overall work will provide a broader view of where we stand and a reference point to compare and evaluate new findings.</p

Selenophene-Modified Boron Dipyrromethene-Based Photosensitizers Exhibit Photodynamic Inhibition on a Broad Range of Bacteria

Microorganisms are crucial for human survival in view of both mutualistic and pathogen interactions. The control of the balance could be achieved by use of the antibiotics. There is a continuous arms race that exists between the pathogen and the antibiotics. The emergence of multidrug-resistant (MDR) bacteria threatens health even for insignificant injuries. However, the discovery of new antibiotics is not a fast process, and the healthcare system will suffer if the evolution of MDR lingers in its current frequency. The cationic photosensitizers (PSs) provide a unique approach to develop novel, light-inducible antimicrobial drugs. Here, we examine the antimicrobial activity of innovative selenophene-modified boron dipyrromethene (BODIPY)-based PSs on a variety of Gram (+) and Gram (−) bacteria. The candidates demonstrate a level of confidence in both light-dependent and independent inhibition of bacterial growth. Among them, selenophene conjugated PS candidates (BOD-Se and BOD-Se-I) are promising agents to induce photodynamic inhibition (PDI) on all experimented bacteria: E. coli, S. aureus, B. cereus, and P. aeruginosa. Further characterizations revealed that photocleavage ability on DNA molecules could be potentially advantageous over extracellular DNA possessing biofilm-forming bacteria such as B. cereus and P. aeruginosa. Microscopy analysis with fluorescent BOD-H confirmed the colocalization on GFP expressing E. coli