Dynamic climate changes pose a significant challenge for plants to cope with numerous abiotic and biotic stressors of increasing intensity. Plants have evolved a variety of biochemical and molecular defense mechanisms involved in overcoming stressful conditions. Under environmental stress, plants generate elevated amounts of reactive oxygen species (ROS) and, subsequently, modulate the activity of the antioxidative enzymes. In addition, an increase in the biosynthesis of important plant compounds such as anthocyanins, lignin, isoflavonoids, as well as a wide range of low molecular weight stress-related proteins (e.g., dehydrins, cyclotides, heat shock proteins and pathogenesis-related proteins), was evidenced. The induced expression of these proteins improves the survival rate of plants under unfavorable environmental stimuli and enhances their adaptation to sequentially interacting stressors. Importantly, the plant defense proteins may also have potential for use in medical applications and agriculture (e.g., biopesticides). Therefore, it is important to gain a more thorough understanding of the complex biological functions of the plant defense proteins. It will help to devise new cultivation strategies, including the development of genotypes characterized by better adaptations to adverse environmental conditions. The review presents the latest research findings on selected plant defense proteins.

Plants face numerous environmental stresses that hinder their growth and productivity, including biotic agents, such as herbivores and parasitic microorganisms, as well as abiotic factors, such as cold, drought, salinity, and high temperature. To counter these challenges, plants have developed a range of defense strategies. Among these, plant antimicrobial proteins and peptides (APPs) have emerged as a promising solution. Due to their broad-spectrum activity, structural stability, and diverse mechanisms of action, APPs serve as powerful tools to complement and enhance conventional agricultural methods, significantly boosting plant defense and productivity. This review focuses on different studies on APPs, emphasizing their crucial role in combating plant pathogens and enhancing plant resilience against both biotic and abiotic stresses. Beginning with in vitro studies, we explore how APPs combat various plant pathogens. We then delve into the defense mechanisms triggered by APPs against biotic stress, showcasing their effectiveness against bacterial and fungal diseases. Additionally, we highlight the role of APPs in mitigating the abiotic challenges associated with climatic change. Finally, we discuss the current applications of APPs in agriculture, emphasizing their potential for sustainable agricultural practices and the need for future research in this area.

Rodents can cause considerable changes in plant community composition. However, relationships between shifts in species dominance and plant functional traits caused by rodents have seldom been investigated, especially for belowground functional traits. In this study, a set of enclosures was constructed to analyze the effects of 10 years of Brandt\'s voles\' activities on the defense strategies and dominant position changes of three gramineous plants (Leymus chinensis, Stipa krylovii, and Cleistogenes squarrosa) in Inner Mongolia. Here, we measured the dominance, biomass, and fourteen functional traits of three plants. The effects of Brandt\'s voles on dominance, biomass, and functional traits were analyzed, and then we explored the effect of functional traits on plant dominance by using the structural equation model. Results showed that long-term feeding by Brandt\'s voles resulted in a significant decrease in the dominance of L. chinensis and S. krylovii, whereas C. squarrosa was positively affected. The belowground biomass of L. chinensis and S. krylovii was higher in the vole treatment, which showed that they were increasing their escape characteristics. The leaf thickness of L. chinensis and the leaf C:N ratio of S. krylovii significantly increased, while the specific leaf area of C. squarrosa significantly decreased. All three gramineous showed increased resistance traits in response to Brandt\'s voles, which positively affected their dominance. Tolerance-related traits of S. krylovii significantly increased, with the increasing growth rate of root length contributing to enhancing its dominance. We highlight that selective feeding by rodents led to the selection of different defense strategies by three gramineous plants, and that changes in biomass allocation and functional traits in the different species affected plant dominance, driving changes in the plant communities.

Gluconacetobacter diazotrophicus is a diazotrophic endophytic bacterium that promotes the growth and development of several plant species. However, the molecular mechanisms activated during plant response to this bacterium remain unclear. Here, we used the RNA-seq approach to understand better the effect of G. diazotrophicus PAL5 on the transcriptome of shoot and root tissues of Arabidopsis thaliana. G. diazotrophicus colonized A. thaliana roots and promoted growth, increasing leaf area and biomass. The transcriptomic analysis revealed several differentially expressed genes (DEGs) between inoculated and non-inoculated plants in the shoot and root tissues. A higher number of DEGs were up-regulated in roots compared to shoots. Genes up-regulated in both shoot and root tissues were associated with nitrogen metabolism, production of glucosinolates and flavonoids, receptor kinases, and transcription factors. In contrast, the main groups of down-regulated genes were associated with pathogenesis-related proteins and heat-shock proteins in both shoot and root tissues. Genes encoding enzymes involved in cell wall biogenesis and modification were down-regulated in shoots and up-regulated in roots. In contrast, genes associated with ROS detoxification were up-regulated in shoots and down-regulated in roots. These results highlight the fine-tuning of the transcriptional regulation of A. thaliana in response to colonization by G. diazotrophicus PAL5.

Citrus is commercially propagated via grafting, which ensures trees have consistent fruit traits combined with favorable traits from the rootstock such as soil adaptability, vigor, and resistance to soil pathogens. Graft incompatibility can occur when the scion and rootstock are not able to form a permanent, healthy union. Understanding and preventing graft incompatibility is of great importance in the breeding of new fruit cultivars and in the choice of scion and rootstock by growers. The rootstock US-1283, a citrandarin generated from a cross of \"Ninkat\" mandarin (Citrus reticulata) and \"Gotha Road\" #6 trifoliate orange (Poncirus trifoliata), was released after years of field evaluation because of its superior productivity and good fruit quality on \"Hamlin\" sweet orange (C. sinensis) under Florida\'s growing conditions. Subsequently, it was observed that trees of \"Bearss\" lemon (C. limon) and \"Valencia\" sweet orange (C. sinensis) grafted onto US-1283 exhibited unhealthy growth near the graft union. The incompatibility manifested as stem grooving and necrosis underneath the bark on the rootstock side of the graft. Another citrandarin rootstock, US-812 (C. reticulata \"Sunki\" × P. trifoliata \"Benecke\"), is fully graft compatible with the same scions. Transcriptome analysis was performed on the vascular tissues above and below the graft union of US-812 and US-1283 graft combinations with \"Bearss\" and \"Valencia\" to identify expression networks associated with incompatibility and help understand the processes and potential causes of incompatibility. Transcriptional reprogramming was stronger in the incompatible rootstock than in the grafted scions. Differentially expressed genes (DEGs) in US-1283, but not the scions, were associated with oxidative stress and plant defense, among others, similar to a pathogen-induced immune response localized to the rootstock; however, no pathogen infection was detected. Therefore, it is hypothesized that this response could have been triggered by signaling miscommunications between rootstock and scion either through (1) unknown molecules from the scion that were perceived as danger signals by the rootstock, (2) missing signals from the scion or missing receptors in the rootstock necessary for the formation of a healthy graft union, (3) the overall perception of the scion by the rootstock as non-self, or (4) a combination of the above.

Nitrogen (N) and silicon (Si) are mineral elements that have shown a reduction in the damage caused by tan spot (Pyrenophora tritici-repentis (Ptr)) in wheat. However, the effects of these elements were studied separately, and the N and Si interaction effect on wheat resistance to tan spot remains elusive. Histocytological and biochemical defense responses against Ptr in wheat leaves treated with Si (+Si) at low (LN) and high N (HN) inputs were investigated. Soil amendment with Si reduced the tan spot severity in 18% due to the increase in the leaf Si concentration (around 30%), but it was affected by the N level used. The superoxide dismutase (SOD) activity was higher in +Si plants and inoculated with Ptr, leading to early and higher H2O2 and callose accumulation in wheat leaf. Interestedly, phenylalanine ammonia-lyase (PAL) activity was induced by the Si supplying, being negatively affected by the HN rate. Meanwhile, catalase (CAT), and peroxidase (POX) activities showed differential response patterns according to the Si and N rates used. Tan spot severity was reduced by both elements, but their interaction does not evidence synergic effects in this disease\'s control. Wheat plants from -Si and HN and +Si and LN treatments recorded lower tan spot severity.

Leaf wounding triggers rapid long-range electrical signaling that initiates systemic defense responses to protect the plants from further attack. In Arabidopsis, this process largely depends on clade three GLUTAMATE RECEPTOR-LIKE (GLR) genes GLR3.3 and GLR3.6. In the cellular context, phloem sieve elements and xylem contact cells where GLRs were mostly present are implicated in the signaling events. In spite of that, the spatial requirements of different leaf cell types for leaf-to-leaf signaling remain poorly investigated. In this study, we dissected cell-type-specific long-distance wound signaling mediated by GLR3s and showed that phloem companion cells are critical in shaping the functions of GLR3.3 and GLR3.6 in the signaling pathway. GLR3.3-mediated response is phloem-specific, during which, GLR3.3 has to be renewed from companion cells to allow its function in sieve elements. GLR3.6 functions dually in ectopic phloem companion cells, in addition to xylem contact cells. Furthermore, the action of GLR3.6 in phloem is independent of its paralog GLR3.3 and probably requires synthesis of GLR3.6 from xylem contact cells. Overall, our work highlights that the phloem companion cell is crucial for both GLRs in controlling leaf-to-leaf electrical signaling.

The cloning of resistance-related genes CsROP5/CsROP10 and the analysis of their mechanism of action provide a theoretical basis for the development of molecular breeding of disease-resistant cucumbers. The structure domains of two Rho-related guanosine triphosphatases from plant (ROP) genes were systematically analyzed using the bioinformatics method in cucumber plants, and the genes CsROP5 (Cucsa.322750) and CsROP10 (Cucsa.197080) were cloned. The functions of the two genes were analyzed using reverse-transcription quantitative PCR (RT-qPCR), virus-induced gene silencing (VIGS), transient overexpression, cucumber genetic transformation, and histochemical staining technology. The conserved elements of the CsROP5/CsROP10 proteins include five sequence motifs (G1-G5), a recognition site for serine/threonine kinases, and a hypervariable region (HVR). The knockdown of CsROP10 through VIGS affected the transcript levels of ABA-signaling-pathway-related genes (CsPYL, CsPP2Cs, CsSnRK2s, and CsABI5), ROS-signaling-pathway-related genes (CsRBOHD and CsRBOHF), and defense-related genes (CsPR2 and CsPR3), thereby improving cucumber resistance to Corynespora cassiicola. Meanwhile, inhibiting the expression of CsROP5 regulated the expression levels of ROS-signaling-pathway-related genes (CsRBOHD and CsRBOHF) and defense-related genes (CsPR2 and CsPR3), thereby enhancing the resistance of cucumber to C. cassiicola. Overall, CsROP5 and CsROP10 may participate in cucumber resistance to C. cassiicola through the ROS and ABA signaling pathways.

Root-knot nematodes are polyphagous parasitic nematodes that cause severe losses in the agriculture worldwide. They enter the root in the elongation zone and subtly migrate to the root meristem where they reach the vascular cylinder and establish a feeding site called gall. Inside the galls they induce a group of transfer cells that serve to nurture them along their parasitic stage, the giant cells. Galls and giant cells develop through a process of post-embryogenic organogenesis that involves manipulating different genetic regulatory networks within the cells, some of them through hijacking some molecular transducers of established plant developmental processes, such as lateral root formation or root regeneration. Galls/giant cells formation involves different mechanisms orchestrated by the nematode´s effectors that generate diverse plant responses in different plant tissues, some of them include sophisticated mechanisms to overcome plant defenses. Yet, the plant-nematode interaction is normally accompanied to dramatic transcriptomic changes within the galls and giant cells. It is therefore expected a key regulatory role of plant-transcription factors, coordinating both, the new organogenesis process induced by the RKNs and the plant response against the nematode. Knowing the role of plant-transcription factors participating in this process becomes essential for a clear understanding of the plant-RKNs interaction and provides an opportunity for the future development and design of directed control strategies. In this review, we present the existing knowledge of the TFs with a functional role in the plant-RKN interaction through a comprehensive analysis of current scientific literature and available transcriptomic data.

Research on plant-nanomaterial interactions has greatly advanced over the past decade. One particularly fascinating discovery encompasses the immunomodulatory effects in plants. Due to the low doses needed and the comparatively low toxicity of many nanomaterials, nanoenabled immunomodulation is environmentally and economically promising for agriculture. It may reduce environmental costs associated with excessive use of chemical pesticides and fertilizers, which can lead to soil and water pollution. Furthermore, nanoenabled strategies can enhance plant resilience against various biotic and abiotic stresses, contributing to the sustainability of agricultural ecosystems and the reduction of crop losses due to environmental factors. While nanoparticle immunomodulatory effects are relatively well-known in animals, they are still to be understood in plants. Here, we provide our perspective on the general components of the plant\'s immune system, including the signaling pathways, networks, and molecules of relevance for plant nanomodulation. We discuss the recent scientific progress in nanoenabled immunomodulation and nanopriming and lay out key avenues to use plant immunomodulation for agriculture. Reactive oxygen species (ROS), the mitogen-activated protein kinase (MAPK) cascade, and the calcium-dependent protein kinase (CDPK or CPK) pathway are of particular interest due to their interconnected function and significance in the response to biotic and abiotic stress. Additionally, we underscore that understanding the plant hormone salicylic acid is vital for nanoenabled applications to induce systemic acquired resistance. It is suggested that a multidisciplinary approach, incorporating environmental impact assessments and focusing on scalability, can expedite the realization of enhanced crop yields through nanotechnology while fostering a healthier environment.