RNAi-mediated stable silencing of TaCSN5 confers broad-spectrum resistance to Puccinia striiformis f. sp. tritici

Ubiquitination of OsCSN5 by OsPUB45 activates immunity by modulating the OsCUL3a-OsNPR1 module

The COP9 signalosome (CSN) is a highly conserved protein complex in eukaryotes, with CSN5 serving as its critical catalytic subunit. However, the role of CSN5 in plant immunity is largely unexplored. Here, we found that suppression of OsCSN5 in rice enhances resistance against the fungal pathogen Magnaporthe oryzae and the bacterial pathogen Xanthomonas oryzae pv. oryzae (Xoo) without affecting growth. OsCSN5 is ubiquitinated and degraded by the E3 ligase OsPUB45. Overexpression of OsPUB45 increased resistance against M. oryzae and Xoo, while dysfunction of OsPUB45 decreased resistance. In addition, OsCSN5 stabilized OsCUL3a to promote the degradation of a positive regulator OsNPR1. Overexpression of OsPUB45 compromised accumulation of OsCUL3a, leading to stabilization of OsNPR1, whereas mutations in OsPUB45 destabilized OsNPR1. These findings suggest that OsCSN5 stabilizes OsCUL3a to facilitate the degradation of OsNPR1, preventing its constitutive activation without infection. Conversely, OsPUB45 promotes the degradation of OsCSN5, contributing to immunity activation upon pathogen infection.

All Roads Lead to Rome: Pathways to Engineering Disease Resistance in Plants

Unlike animals, plants are unable to move and lack specialized immune cells and circulating antibodies. As a result, they are always threatened by a large number of microbial pathogens and harmful pests that can significantly reduce crop yield worldwide. Therefore, the development of new strategies to control them is essential to mitigate the increasing risk of crops lost to plant diseases. Recent developments in genetic engineering, including efficient gene manipulation and transformation methods, gene editing and synthetic biology, coupled with the understanding of microbial pathogenicity and plant immunity, both at molecular and genomic levels, have enhanced the capabilities to develop disease resistance in plants. This review comprehensively explains the fundamental mechanisms underlying the tug-of-war between pathogens and hosts, and provides a detailed overview of different strategies for developing disease resistance in plants. Additionally, it provides a summary of the potential genes that can be employed in resistance breeding for key crops to combat a wide range of potential pathogens and pests, including fungi, oomycetes, bacteria, viruses, nematodes, and insects. Furthermore, this review addresses the limitations associated with these strategies and their possible solutions. Finally, it discusses the future perspectives for producing plants with durable and broad-spectrum disease resistance.

Advances in RNA Interference for Plant Functional Genomics: Unveiling Traits, Mechanisms, and Future Directions

RNA interference (RNAi) is a conserved molecular mechanism that plays a critical role in post-transcriptional gene silencing across diverse organisms. This review delves into the role of RNAi in plant functional genomics and its applications in crop improvement, highlighting its mechanistic insights and practical implications. The review begins with the foundational discovery of RNAi's mechanism, tracing its origins from petunias to its widespread presence in various organisms. Various classes of regulatory non-coding small RNAs, including siRNAs, miRNAs, and phasiRNAs, have been uncovered, expanding the scope of RNAi-mediated gene regulation beyond conventional understanding. These RNA classes participate in intricate post-transcriptional and epigenetic processes that influence gene expression. In the context of crop enhancement, RNAi has emerged as a powerful tool for understanding gene functions. It has proven effective in deciphering gene roles related to stress resistance, metabolic pathways, and more. Additionally, RNAi-based approaches hold promise for integrated pest management and sustainable agriculture, contributing to global efforts in food security. This review discusses RNAi's diverse applications, such as modifying plant architecture, extending shelf life, and enhancing nutritional content in crops. The challenges and future prospects of RNAi technology, including delivery methods and biosafety concerns, are also explored. The global landscape of RNAi research is highlighted, with significant contributions from regions such as China, Europe, and North America. In conclusion, RNAi remains a versatile and pivotal tool in modern plant research, offering novel avenues for understanding gene functions and improving crop traits. Its integration with other biotechnological approaches such as gene editing holds the potential to shape the future of agriculture and sustainable food production.

The Calcium-Dependent Protein Kinase TaCDPK7 Positively Regulates Wheat Resistance to Puccinia striiformis f. sp. tritici

Ca2+ plays a crucial role as a secondary messenger in plant development and response to abiotic/biotic stressors. Calcium-dependent protein kinases (CDPKs/CPKs) are essential Ca2+ sensors that can convert Ca2+ signals into downstream phosphorylation signals. However, there is limited research on the function of CDPKs in the context of wheat-Puccinia striiformis f. sp. tritici (Pst) interaction. In this study, we aimed to address this gap by identifying putative CDPK genes from the wheat reference genome and organizing them into four phylogenetic clusters (I-IV). To investigate the expression patterns of the TaCDPK family during the wheat-Pst interaction, we analyzed time series RNA-seq data and further validated the results through qRT-PCR assays. Among the TaCDPK genes, TaCDPK7 exhibited a significant induction during the wheat-Pst interaction, suggesting that it has a potential role in wheat resistance to Pst. To gain further insights into the function of TaCDPK7, we employed virus-induced gene silencing (VIGS) to knock down its expression which resulted in impaired wheat resistance to Pst, accompanied by decreased accumulation of hydrogen peroxide (H2O2), increased fungal biomass ratio, reduced expression of defense-related genes, and enhanced pathogen hyphal growth. These findings collectively suggest that TaCDPK7 plays an important role in wheat resistance to Pst. In summary, this study expands our understanding of wheat CDPKs and provides novel insights into their involvement in the wheat-Pst interaction.

The Wheat Annexin TaAnn12 Plays Positive Roles in Plant Disease Resistance by Regulating the Accumulation of Reactive Oxygen Species and Callose

(1) Annexins are proteins that bind phospholipids and calcium ions in cell membranes and mediate signal transduction between Ca2+ and cell membranes. They play key roles in plant immunity. (2) In this study, virus mediated gene silencing and the heterologous overexpression of TaAnn12 in Arabidopsis thaliana Col-0 trials were used to determine whether the wheat annexin TaAnn12 plays a positive role in plant disease resistance. (3) During the incompatible interaction between wheat cv. Suwon 11 and the Puccinia striiformis f. sp. tritici (Pst) race CYR23, the expression of TaAnn12 was significantly upregulated at 24 h post inoculation (hpi). Silencing TaAnn12 in wheat enhanced the susceptibility to Pst. The salicylic acid hormone contents in the TaAnn12-silenced plants were significantly reduced. The overexpression of TaAnn12 in A. thaliana significantly increased resistance to Pseudomonas syringae pv. tomato DC3000, and the symptoms of the wild-type plants were more serious than those of the transgenic plants; the amounts of bacteria were significantly lower than those in the control group, the accumulation of Reactive Oxygen Species (ROS)and callose deposition increased, and the expression of resistance-related genes (AtPR1, AtPR2, and AtPR5) significantly increased. (4) Our results suggest that wheat TaAnn12 resisted the invasion of pathogens by inducing the production and accumulation of ROS and callose.

Transcriptome-Wide Integrated Analysis of the PgGT25-04 Gene in Controlling Ginsenoside Biosynthesis in Panax ginseng

Panax ginseng is a valuable medicinal herb of the Araliaceae family with various pharmacological activities. The Trihelix transcription factors family is involved in growth and secondary metabolic processes in plants, but no studies have been reported on the involvement of Trihelix genes in secondary metabolic processes in ginseng. In this study, weighted co-expression network analysis, correlation analysis between PgGTs and ginsenosides and key enzyme genes, and interaction network analysis between PgGTs and key enzyme genes were used to screen out the PgGT25-04 gene, which was negatively correlated with ginsenoside synthesis. Using ABA treatment of ginseng hair roots, PgGT genes were found to respond to ABA signals. Analysis of the sequence characteristics and expression pattern of the PgGT25-04 gene in ginseng revealed that its expression is spatiotemporally specific. The interfering vector pBI121-PgGT25-04 containing the PgGT25-04 gene was constructed, and the ginseng adventitious roots were transformed using the Agrobacterium-mediated method to obtain the pBI121-PgGT25-04 positive hairy root monocot line. The saponin contents of positive ginseng hair roots were measured by HPLC, and the changes in PgGT25-04 and key enzyme genes in positive ginseng hair roots were detected via fluorescence quantitative RT-PCR. These results preliminarily identified the role of the PgGT25-04 gene in the secondary metabolism of ginseng in Jilin to provide a theoretical basis for the study of Trihelix transcription factors in Panax ginseng.

Engineering plant immune circuit: walking to the bright future with a novel toolbox

Plant pathogens destroy crops and cause severe yield losses, leading to an insufficient food supply to sustain the human population. Apart from relying on natural plant immune systems to combat biological agents or waiting for the appropriate evolutionary steps to occur over time, researchers are currently seeking new breakthrough methods to boost disease resistance in plants through genetic engineering. Here, we summarize the past two decades of research in disease resistance engineering against an assortment of pathogens through modifying the plant immune components (internal and external) with several biotechnological techniques. We also discuss potential strategies and provide perspectives on engineering plant immune systems for enhanced pathogen resistance and plant fitness.

Small RNA-based plant protection against diseases

Plant diseases cause significant decreases in yield and quality of crops and consequently pose a very substantial threat to food security. In the continuous search for environmentally friendly crop protection, exploitation of RNA interferance machinery is showing promising results. It is well established that small RNAs (sRNAs) including microRNA (miRNA) and small interfering RNA (siRNA) are involved in the regulation of gene expression via both transcriptional and post-transcriptional RNA silencing. sRNAs from host plants can enter into pathogen cells during invasion and silence pathogen genes. This process has been exploited through Host-Induced Gene Silencing (HIGS), in which plant transgenes that produce sRNAs are engineered to silence pest and pathogen genes. Similarly, exogenously applied sRNAs can enter pest and pathogen cells, either directly or via the hosts, and silence target genes. This process has been exploited in Spray-Induced Gene Silencing (SIGS). Here, we focus on the role of sRNAs and review how they have recently been used against various plant pathogens through HIGS or SIGS-based methods and discuss advantages and drawbacks of these approaches.

A candidate effector protein PstCFEM1 contributes to virulence of stripe rust fungus and impairs wheat immunity

Common in Fungal Extracellular Membrane (CFEM) domain proteins are considered to be unique to fungi and closely related to pathogenicity. However, the Puccinia striiformis f. sp. tritici (Pst) effector containing the CFEM domain has not been reported. Here, we obtained an effector, PstCFEM1, containing a functional N-terminal signal peptide sequence and the CFEM domain from Pst race CYR31. qRT-PCR assay indicated that the transcript levels of PstCFEM1 were highly induced during the early stages of infection. Overexpression of PstCFEM1 suppressed Pst322 (an elicitor-like protein of Pst)-trigged cell death, reactive oxygen species (ROS) accumulation and callose deposition. Host-induced gene silencing (HIGS) experiments showed that knockdown of PstCFEM1 decreased the virulence of Pst, while ROS accumulation in silenced plants increased near the infection site. In addition, wheat containing the PstCFEM1-silenced construct increased resistance to multiple races of Pst. Our data suggest that PstCFEM1 suppresses wheat defense by inhibiting ROS accumulation and contributes to increased virulence of Pst.

Transcription factor BZR2 activates chitinase Cht20.2 transcription to confer resistance to wheat stripe rust

The brassinosteroid pathway promotes a variety of physiological processes in plants and the brassinosteroid insensitive1-ethylmethane sulfonate suppressor (BES)/brassinazole-resistant (BZR) functions as one of its key regulators. We previously showed that the BES/BZR-type transcription factor TaBZR2 mediates the drought stress response in wheat (Triticum aestivum) by directly upregulating the transcriptional activity of glutathione S-transferase 1. However, the function of TaBZR2 in plants under biotic stresses is unknown. In this study, we found that transcript levels of TaBZR2 were upregulated in response to inoculation with wheat stripe rust fungus (Puccinia striiformis f. sp. tritici, Pst) and treatment with flg22 or an elicitor-like protein of Pst, Pst322. Wheat lines overexpressing TaBZR2 conferred increased resistance, whereas TaBZR2-RNAi lines exhibited decreased resistance to multiple races of Pst. TaBZR2 targeted the promoter of the chitinase gene TaCht20.2, activating its transcription. Knockdown of TaCht20.2 in wheat resulted in enhanced susceptibility to Pst, indicating the positive role of TaCht20.2 in wheat resistance. Upon Pst infection in vivo, the overexpression of TaBZR2 increased total chitinase activity, whereas RNAi-mediated silencing of TaBZR2 reduced total chitinase activity. Taken together, our results suggest that TaBZR2 confers broad-spectrum resistance to the stripe rust fungus by increasing total chitinase activity in wheat.