Structure-function analyses of coiled-coil immune receptors define a hydrophobic module for improving plant virus resistance

Advances in understanding the interaction between Solanaceae NLR resistance proteins and the viral effector Avr

The rising prevalence of viral-induced diseases, particularly those caused by certain strains, poses a substantial risk to the genetic diversity of Solanaceae crops and the overall safety of horticultural produce. According to the "gene-for-gene" hypothesis, resistance proteins are capable of selectively identifying nontoxic effectors produced by pathogens, as they are under purview of the host's immune defenses. The sensitivity and responsiveness of Solanaceae plants to viral attacks play a crucial role in shaping the outcomes of their interactions with viruses. Pathogenic organisms, devise an array of infection tactics aimed at circumventing or neutralizing the host's immune defenses to facilitate effective invasion. The invasion often accomplishes by suppressing or disrupting the host's defensive mechanisms or immune signals, which are integral to the infection strategies of such invading pathogens. This comprehensive review delves into the myriad approaches that pathogenic viruses employ to infiltrate and overcome the sophisticated immune system of tomatoes. Furthermore, the review explores the possibility of utilizing these viral strategies to bolster the resilience of horticultural crops, presenting a hopeful direction for forthcoming progress in plant health and agricultural stability.

Development and application of sugarcane streak mosaic virus vectors

Sugarcane streak mosaic virus (SCSMV) is one of the major pathogens of sugarcane in the world. Molecular studies and disease management of SCSMV are hindered by the lack of efficient infectious clones. In this study, we successfully constructed Agrobacterium infiltration based infectious clone of SCSMV with different variants. Infectious clones of wild type SCSMV could efficiently infect Nicotiana benthamiana and sugarcane plants resulting in streak and mosaic symptoms on systemic leaves which were further confirmed with RT-PCR and serological assays. SCSMV variants of less adenylation displayed attenuated pathogenicity on N.benthamiana. SCSMV-based recombinant heterologous EGFP protein vector was also developed. The EGFP-tagged recombinant SCSMV could highly expressed in vegetative organs including roots. These infectious clones of SCSMV could be further developed for platform tools for both biotechnological studies and management of SCSMV disease.

Plant virology in the 21st century in China: Recent advances and future directions

Plant viruses are a group of intracellular pathogens that persistently threaten global food security. Significant advances in plant virology have been achieved by Chinese scientists over the last 20 years, including basic research and technologies for preventing and controlling plant viral diseases. Here, we review these milestones and advances, including the identification of new crop-infecting viruses, dissection of pathogenic mechanisms of multiple viruses, examination of multilayered interactions among viruses, their host plants, and virus-transmitting arthropod vectors, and in-depth interrogation of plant-encoded resistance and susceptibility determinants. Notably, various plant virus-based vectors have also been successfully developed for gene function studies and target gene expression in plants. We also recommend future plant virology studies in China.

Near-infrared light and PIF4 promote plant antiviral defense by enhancing RNA interference

The molecular mechanism underlying phototherapy and light treatment, which utilize various wavelength spectra of light, including near-infrared (NIR), to cure human and plant diseases, is obscure. Here we revealed that NIR light confers antiviral immunity by positively regulating PHYTOCHROME-INTERACTING FACTOR 4 (PIF4)-activated RNA interference (RNAi) in plants. PIF4, a central transcription factor involved in light signaling, accumulates to high levels under NIR light in plants. PIF4 directly induces the transcription of two essential components of RNAi, RNA-DEPENDENT RNA POLYMERASE 6 (RDR6) and ARGONAUTE 1 (AGO1), which play important roles in resistance to both DNA and RNA viruses. Moreover, the pathogenic determinant βC1 protein, which is evolutionarily conserved and encoded by betasatellites, interacts with PIF4 and inhibits its positive regulation of RNAi by disrupting PIF4 dimerization. These findings shed light on the molecular mechanism of PIF4-mediated plant defense and provide a new perspective for the exploration of NIR antiviral treatment.

Characterization of gene expression patterns in response to an orthotospovirus infection between two diploid peanut species and their hybrid

Tomato spotted wilt orthotospovirus (TSWV) transmitted by thrips causes significant yield loss in peanut (Arachis hypogaea L.) production. Use of peanut cultivars with moderate field resistance has been critical for TSWV management. However, current TSWV resistance is often not adequate, and the availability of sources of tetraploid resistance to TSWV is very limited. Allotetraploids derived by crossing wild diploid species could help introgress alleles that confer TSWV resistance into cultivated peanut. Thrips-mediated TSWV screening identified two diploids and their allotetraploid possessing the AA, BB, and AABB genomes Arachis stenosperma V10309, Arachis valida GK30011, and [A. stenosperma × A. valida]4x (ValSten1), respectively. These genotypes had reduced TSWV infection and accumulation in comparison with peanut of pure cultivated pedigree. Transcriptomes from TSWV-infected and non-infected samples from A. stenosperma, A. valida, and ValSten1 were assembled, and differentially expressed genes (DEGs) following TSWV infection were assessed. There were 3,196, 8,380, and 1,312 significant DEGs in A. stenosperma, A. valida, and ValSten1, respectively. A higher proportion of genes decreased in expression following TSWV infection for A. stenosperma and ValSten1, whereas a higher proportion of genes increased in expression following infection in A. valida. The number of DEGs previously annotated as defense-related in relation to abiotic and biotic stress was highest in A. valida followed by ValSten1 and A. stenosperma. Plant phytohormone and photosynthesis genes also were differentially expressed in greater numbers in A. valida followed by ValSten1 and A. stenosperma, with over half of those exhibiting decreases in expression.

Protein stability governed by α1-2 helices in Pvr4 is essential for localization and cell death

Plant nucleotide-binding domain leucine-rich-repeat receptor (NLR) confers disease resistance to various pathogens by recognizing effectors derived from the pathogen. Previous studies have shown that overexpression of the CC domain in several NLRs triggers cell death, implying that the CC domain plays an important role as a signaling module. However, how CC domain transduces immune signals remains largely unknown. A Potyvirus-resistant NLR protein, Pvr4, possesses a CC domain (CCPvr4 ) that induces cell death upon transient overexpression in Nicotiana benthamiana. In this study, loss-of-function mutants were generated by error-prone PCR-based random mutagenesis to understand the molecular mechanisms underlying CCPvr4 -mediated cell death. Cell biology and biochemical studies revealed that M16 and Q52 in the α1 and α2 helices, respectively, are crucial for protein stability, and mutation of these residues disrupts localization to the plasma membrane and oligomerization activity. The increase of the protein stability of these mutants by tagging a green fluorescent protein (GFP) variant led to restoration of cell death-inducing activity and plasma membrane localization. Another mutant, I7E in the very N-terminal region, lost cell death-inducing activity by weakening the interaction with plasma membrane H+ -ATPase compared to CCPvr4 , although the protein remained in the plasma membrane. Moreover, most of the mutated residues are on the outer surface of the funnel shape in the predicted pentameric CCPvr4 , implying that the disordered N-terminal region plays a crucial role in association with PMA as well as targeting to the plasma membrane. This work could provide insights into the molecular mechanisms of cell death induced by NLR immune receptors.

NLR immune receptors: structure and function in plant disease resistance

Nucleotide-binding and leucine-rich repeat receptors (NLRs) are a diverse family of intracellular immune receptors that play crucial roles in recognizing and responding to pathogen invasion in plants. This review discusses the overall model of NLR activation and provides an in-depth analysis of the different NLR domains, including N-terminal executioner domains, the nucleotide-binding oligomerization domain (NOD) module, and the leucine-rich repeat (LRR) domain. Understanding the structure-function relationship of these domains is essential for developing effective strategies to improve plant disease resistance and agricultural productivity.