Variation in the LRR region of Pi54 protein alters its interaction with the AvrPi54 protein revealed by in silico analysis

Recent Advances in Effector Research of Magnaporthe oryzae

Recalcitrant rice blast disease is caused by Magnaporthe oryzae, which has a significant negative economic reverberation on crop productivity. In order to induce the disease onto the host, M. oryzae positively generates many types of small secreted proteins, here named as effectors, to manipulate the host cell for the purpose of stimulating pathogenic infection. In M. oryzae, by engaging with specific receptors on the cell surface, effectors activate signaling channels which control an array of cellular activities, such as proliferation, differentiation and apoptosis. The most recent research on effector identification, classification, function, secretion, and control mechanism has been compiled in this review. In addition, the article also discusses directions and challenges for future research into an effector in M. oryzae.

Understanding the Dynamics of Blast Resistance in Rice-Magnaporthe oryzae Interactions

Rice is a global food grain crop for more than one-third of the human population and a source for food and nutritional security. Rice production is subjected to various stresses; blast disease caused by Magnaporthe oryzae is one of the major biotic stresses that has the potential to destroy total crop under severe conditions. In the present review, we discuss the importance of rice and blast disease in the present and future global context, genomics and molecular biology of blast pathogen and rice, and the molecular interplay between rice–M. oryzae interaction governed by different gene interaction models. We also elaborated in detail on M. oryzae effector and Avr genes, and the role of noncoding RNAs in disease development. Further, rice blast resistance QTLs; resistance (R) genes; and alleles identified, cloned, and characterized are discussed. We also discuss the utilization of QTLs and R genes for blast resistance through conventional breeding and transgenic approaches. Finally, we review the demonstrated examples and potential applications of the latest genome-editing tools in understanding and managing blast disease in rice.

A Putative D-Arabinono-1,4-lactone Oxidase, MoAlo1, Is Required for Fungal Growth, Conidiogenesis, and Pathogenicity in Magnaporthe oryzae

Magnaporthe oryzae is the causal agent of rice blast outbreaks. L-ascorbic acid (ASC) is a famous antioxidant found in nature. However, while ASC is rare or absent in fungi, a five-carbon analog, D-erythroascorbic acid (EASC), seems to appear to be a substitute for ASC. Although the antioxidant function of ASC has been widely described, the specific properties and physiological functions of EASC remain poorly understood. In this study, we identified a D-arabinono-1,4-lactone oxidase (ALO) domain-containing protein, MoAlo1, and found that MoAlo1 was localized to mitochondria. Disruption of MoALO1 (ΔMoalo1) exhibited defects in vegetative growth as well as conidiogenesis. The ΔMoalo1 mutant was found to be more sensitive to exogenous H₂O₂. Additionally, the pathogenicity of conidia in the ΔMoalo1 null mutant was reduced deeply in rice, and defective penetration of appressorium-like structures (ALS) formed by the hyphal tips was also observed in the ΔMoalo1 null mutant. When exogenous EASC was added to the conidial suspension, the defective pathogenicity of the ΔMoalo1 mutant was restored. Collectively, MoAlo1 is essential for growth, conidiogenesis, and pathogenicity in M. oryzae.

A genome-wide survey of interaction between rice and Magnaporthe oryzae via microarray analysis

The main aim of the work is to study the regulation of gene expression in the interaction between rice and Magnaporthe oryzae by gene chip technology. In this study, we mainly focused on changes of gene expression at 24, 48, and 72 hours post-inoculation (hpi), through which we could conduct a more comprehensive analysis of rice blast-related genes in the process of infection. The results showed that the experimental groups contained 460, 1227, and 3937 significant differentially expressed genes at 24, 48, and 72 hpi, respectively. Furthermore, 115 significantly differentially expressed genes were identified in response to rice blast infection at all three time points. By annotating these 115 genes, they were divided into three categories: metabolic pathways, proteins or enzymes, and organelle components. As expected, many of these genes were known rice blast-related genes; however, we discovered new genes with high fold changes. Most of them encoded conserved hypothetical proteins, and some were hypothetically conserved genes. Our study may contribute to finding new resistance genes and understanding the mechanism of rice blast development.

In silico modelling and characterization of eight blast resistance proteins in resistant and susceptible rice cultivars

Background

Nucleotide-binding site-leucine-rich repeat (NBS-LRR) resistance genes are the largest class of plant resistance genes which play an important role in the plant defense response. These genes are better conserved than others and function as a recognition-based immune system in plants through their encoded proteins.

Results

Here, we report the effect of Magnaporthe oryzae, the rice blast pathogen inoculation in resistant BR2655 and susceptible HR12 rice cultivars. Transcriptomic profiling was carried out to analyze differential gene expression in these two cultivars. A total of eight NBS-LRR uncharacterized resistance proteins (RP1, RP2, RP3, RP4, RP5, RP6, RP7, and RP8) were selected in these two cultivars for in silico modeling. Modeller 9.22 and SWISS-MODEL servers were used for the homology modeling of eight RPs. ProFunc server was utilized for the prediction of secondary structure and function. The CDvist Web server and Interpro scan server detected the motif and domains in eight RPs. Ramachandran plot of eight RPs confirmed that the modeled structures occupied favorable positions.

Conclusions

From the present study, computational analysis of these eight RPs may afford insights into their role, function, and valuable resource for studying the intricate details of the plant defense mechanism. Furthermore, the identification of resistance proteins is useful for the development of molecular markers linked to resistance genes.

Supplementary Information

The online version contains supplementary material available at 10.1186/s43141-020-00076-0.

Design, Synthesis, Crystal Structure, and Fungicidal Activity of Two Fenclorim Derivatives

Two fenclorim derivatives (compounds 6 and 7) were synthesized by linking active sub-structures using fenclorim as the lead compound. The chemical structures of the two compounds were confirmed by NMR spectroscopy, high resolution mass spectrometry, and X-ray diffraction analysis. Their fungicidal activity against six plant fungal strains was tested. Compounds 6 and 7 both crystallized in the monoclinic system, with a P21/c space group (a = 8.4842(6) Å, b = 24.457(2) Å, c = 8.9940(6) Å, V = 1855.0(2) Å3, Z = 4) and Cc space group (a = 10.2347(7) Å, b = 18.3224(10) Å, c = 7.2447(4) Å, V = 1357.50(14) Å3, Z = 4), respectively. The crystal structure of compound 6 was stabilized by C–H···N and C–H···O hydrogen bonding interactions and N–H···N hydrogen bonds linked the neighboring molecules of compound 7 to form a three-dimensional framework. Compound 6 displayed the most excellent activity, which is much better than that of pyrimethanil against Botrytis cinerea in vivo. Additionally, compound 6 exhibited greater in vitro activity against Pseudoperonospora cubensis compared to that of pyrimethanil. Moreover, compound 7 exhibited strong fungicidal activity against Erysiphe cichoracearum at 50 mg/L in vitro, while pyrimethanil did not. Compounds 6 and 7 could be used as new pyrimidine fungicides in the future.