Understanding the role of cysteine-rich receptor-like kinases (CRKs) in plant defense mechanisms is crucial for enhancing wheat resistance to leaf rust fungus infection. Here, we identified and verified 164 members of the CRK gene family using the Triticum aestivum reference version 2 collected from the international wheat genome sequencing consortium (IWGSC). The proteins exhibited characteristic features of CRKs, including the presence of signal peptides, cysteine-rich/stress antifungal/DUF26 domains, transmembrane domains, and Pkinase domains. Phylogenetic analysis revealed extensive diversification within the wheat CRK gene family, indicating the development of distinct specific functional roles to wheat plants. When studying the expression of the CRK gene family in near-isogenic lines (NILs) carrying Lr57- and Lr14a-resistant genes, Puccinia triticina, the causal agent of leaf rust fungus, triggered temporal gene expression dynamics. The upregulation of specific CRK genes in the resistant interaction indicated their potential role in enhancing wheat resistance to leaf rust, while contrasting gene expression patterns in the susceptible interaction highlighted potential susceptibility associated CRK genes. The study uncovered certain CRK genes that exhibited expression upregulation upon leaf rust infection and the Lr14a-resistant gene. The findings suggest that targeting CRKs may present a promising strategy for improving wheat resistance to rust diseases.

The plant plasma membrane serves as the primary interface for perceiving extracellular signals, a function largely mediated by plasma membrane receptors (PMRs). In wheat (Triticum aestivum), the functional characterization of these receptors is impeded by the species’ large, hexaploid genome, which results in extensive gene duplication and functional redundancy. This review synthesizes current knowledge on wheat PMRs, covering their diversity, classification, and signaling mechanisms, with a particular emphasis on their central role in plant immunity. We highlight the remarkable structural and functional diversification of PMR families, which range in size from 10 members, as seen in the case of wheat leaf rust kinase (WLRK), to over 3424 members in the receptor-like kinase (RLK) family. Furthermore, we reviewed the role of PMRs in being critical for detecting a wide array of biotic stimuli, including pathogen-associated molecular patterns (PAMPs), herbivore-associated molecular patterns (HAMPs), and symbiotic signals. Upon perception, PMRs initiate downstream signaling cascades that orchestrate defense responses, including transcriptional reprogramming, cell wall reinforcement, and metabolic changes. The review also examines the complex cross-talk between immune receptors and other signaling pathways, such as those mediated by brassinosteroid and jasmonic acid receptors, which underpin the delicate balance between growth and defense. Finally, we bridge these fundamental insights to applications in crop improvement, delineating strategies like marker-assisted selection, gene stacking, and receptor engineering to enhance disease resistance. After identifying key obstacles such as genetic redundancy and pleiotropic effects, we propose future research directions that leverage multi-omics, systems biology, and synthetic biology to fully unlock the potential of wheat PMRs for sustainable agriculture.

Pseudomonas fluorescens is one of plant Growth Promoting Rhizobacteria (PGPR) members which has a major role in the biological control of bacterial and fungal pathogens. A research was conducted at the Laboratory of Microbiology, Faculty of Agriculture, Ain Shams University, Qalubyia governorate intended for isolating Pseudomonas fluorescens isolate, efficient in antibiotic production. For isolation, soil samples, collected from Faculty of agriculture farm soil at depth of 10 cm, were screened for Ps. fluorescens isolates by cultivating the samples on King’s medium. Out of 30 isolates obtained, one was selected based on its high lipid content, because of the lipid’s correlation to antibiotic production and inhibitory activity. The selected isolate was characterized by morphological, physiological, biochemical tests then confirmed its identity by 16S rRNA gene sequence analysis and named Pseudomonas fluorescens NBRC-14160 16srRNA. Morphological features showed that Ps. fluorescens NBRC-14160 has large colonies, with irregular surface, opaque, producing green fluorescent pigments. Cells are short rods, Gram negative. Physiological features indicated that Ps. fluorescens NBRC-14160 is capable of producing several exo-enzymes including lipase, phospholipase, protease and chitinase and incapable of producing amylase and cellulase. Carbohydrate fermentation tests were positive for fructose, glucose, D-glucose, and galactose, forming acids after 24 hrs. of incubation at 30˚C. However, it loses the ability to ferment inositol, mannose, xylose, mannitol, raffinose and rhamnose sugars. It’s lipid content was 607 mg/g. Inhibitory activity was studied by the method of disc diffusion test against nine pathogenic bacterial and fungal strains. Staphylococcus aureus was the most sensitive bacterial pathogen towards P. fluorescens NBRC-14160 with a 4.5 cm zone of inhibition, while Serratia marscens had 0.95 cm zone. Aspergillus niger and Alternaria solani were the most sensitive fungal pathogens towards P. fluorescens NBRC-14160 with 2.55 and 2.5 cm of inhibition zone, respectively. However, the most resistant fungus was Fusarium oxysporum with 1.3 cm inhibition zone.