Phenylalanine Ammonia-lyase Research Articles

Induced resistance to control postharvest stem-end rot by methyl jasmonate in mango fruit

Induced resistance is an alternative disease control strategy for postharvest fruits and vegetables. Methyl jasmonate (MeJA) is a crucial phytohormone in the defense response to biotic and abiotic stresses. The effect and relevant mechanism of MeJA on the control of postharvest disease in mango fruit remain unclear. This study investigated the effect and possible mechanism of MeJA against stem-end rot caused by Lasiodiplodia theobromae in mango fruit. The results showed that MeJA significantly inhibited the lesion expansion on mango fruit inoculated with L. theobromae. 10 μM MeJA treatment effectively induced disease resistance against L. theobromae during postharvest storage. MeJA enhanced the activities of defense-related enzymes, including phenylalanine ammonia lyase (PAL), peroxidase (POD), β-1,3-glucanase (GLU), and chitinase (CHT), increased the accumulation of endogenous jasmonic acid (JA) and salicylic acid (SA) contents, up-regulated the expressions of the related genes on JA pathway (AOS, JAR1, MYC2, and COI1) and SA pathway (ICS, and PR1), stimulated the contents of total phenolics and flavonoids, and inhibited the accumulation of malondialdehyde (MDA). Furthermore, MeJA delayed the ripening and senescence of the fruit by inhibiting the peel yellowing, flesh softening and change in soluble solids content (SSC) of mango fruit. The results indicated that the enhanced resistance of MeJA-treated mango to stem-end rot was potentially due to the activation of defense responses induced by synergistic interaction between JA and SA pathways, as well as delayed postharvest ripening. The MeJA treatment is a promising strategy to control stem-end rot of mango fruit.

Exogenous p-coumaric acid treatment improves phenolic compounds biosynthesis of postharvest cherry tomatoes by regulating physiological metabolism.

To investigate the effect of p-coumaric acid (p-CA) on postharvest cherry tomatoes, breaker stage fruits were treated with p-CA to analyze the physiological metabolism during storage. The results showed that exogenous p-CA treatment improved the sensory quality of tomato fruits. Transcriptomics results indicated that 782 genes (339 up-regulated and 443 down-regulated) were differentially expressed between p-CA treated and control fruits. Results suggested that p-CA treatment regulated the synthesis of phenolic compounds and inhibited the fruit ripening through the pathways of mangiferic acid biosynthesis and phenylalanine metabolism. Key enzymes activities of the phenylpropane metabolic pathway of tomato fruits were increased, including phenylalanine ammonia lyase (PAL), cinnamic acid 4-hydroxylase (C4H), and 4-coumarate-CoA ligase (4CL). In addition, the total phenols content, flavonoids content and antioxidant capacities of tomato fruits were improved with p-CA treatment. Overall, these findings showed that p-CA treatment could be a potential strategy for fruit and vegetable preservation.

Direct asymmetric synthesis of β-branched aromatic α-amino acids using engineered phenylalanine ammonia lyases

β-Branched aromatic α-amino acids are valuable building blocks in natural products and pharmaceutically active compounds. However, their chemical or enzymatic synthesis is challenging due to the presence of two stereocenters. We design phenylalanine ammonia lyases (PAL) variants for the direct asymmetric synthesis of β-branched aromatic α-amino acids. Based on extensive computational analyses, we unravel the enigma behind PAL’s inability to accept β-methyl cinnamic acid (β-MeCA) as substrate and achieve the synthesis of the corresponding amino acids of β-MeCA and analogs using a double (PcPAL-L256V-I460V) and a triple mutant (PcPAL-F137V-L256V-I460V). The reactions are scaled-up using an optimized E. coli based whole-cell biotransformation system to produce ten β-branched phenylalanine analogs with high diastereoselectivity (dr > 20:1) and enantioselectivity (ee > 99.5%) in yields ranging from 41-71%. Moreover, we decipher the mechanism of PcPAL-L256V-I460V for the acceptance of β-MeCA and converting it with excellent stereoselectivity by computational simulations. Thus, this study offers an efficient method for synthesizing β-branched aromatic α-amino acids.

Understanding the Effect of Ionic Liquid-Mediated Solvent Engineering on the Kinetics and Thermodynamic Stability of Phenylalanine Ammonia-Lyase.

Phenylalanine ammonia-lyase (PAL) plays a central role in the phenylpropanoid pathway and in the treatment of phenylketonuria. However, the integration of PAL into sustainable industrial biocatalysis is hampered by its instability under harsh conditions. This study demonstrates that ionic liquid (IL)-assisted solvent (Tris-HCl buffer) engineering enables improvement of the reaction kinetics and thermodynamic stability of Rhodotorula glutinisPAL (RgPAL) under various stresses. Under optimized conditions, a 66.2% higher Kcat value, >60% remaining activity after 5 weeks of storage at room temperature, and >80% activity of RgPAL after incubation at 60 °C for 1 h were obtained in the [Ch][Ac]-blended Tris-HCl solvent compared to pristine Tris-HCl. The spectroscopic and molecular docking results suggest that the higher extent of hydration and the soft interactions complemented by the ILs with the D-chain residues of RgPAL jointly contributed to achieving more stable and active conformations of RgPAL. The enzyme showed a higher melting temperature (Tm) in ILs+Tris-HCl compared to that in pristine Tris-HCl, with less change in enthalpy (ΔHfu) and entropy (ΔSfu) of unfolding. Overall, IL-mediated solvent engineering alters the microenvironment of RgPAL and allows the development of a robust PAL-based biocatalytic system.

Effects of Efficient Ethylene Remover on the Lignification of Fresh Faba Bean (Vicia faba L.) during Storage.

Postharvest ethylene accumulation and lignification are significant issues affecting the storage quality of fresh faba beans, resulting in rapid quality decline. However, there is still a lack of effective preservation methods to preserve the quality of faba beans during storage. This study aimed to investigate the regulation of lignification in faba beans during storage using a high-efficiency ethylene remover (HEER), examining physiological responses, key enzyme activities, and transcriptomic changes. Results showed that the HEER treatment inhibited the lignification, reducing it by 45% and lowering the respiratory rate of fresh pods by 32.8% during storage. Additionally, the HEER treatment suppressed respiration rates and the activities of lignin synthesis-related enzymes, including phenylalanine ammonia-lyase (from 353.73 to 246.60 U/g), cinnamic acid-4-hydroxylase (from 635.86 to 125.00 U/g), 4-coumarate: coenzyme A ligase (from 1008.57 to 516.52 U/g), and cinnamyl-alcohol dehydrogenase (from 129.42 to 37.12 U/g), thus slowing lignin accumulation. During storage, the hardness of fresh faba bean increased by 9.79% from the initial period, being 1.44 times higher than that of HEER. On days 8 and 16 of storage, the respiratory rate of the treated beans decreased by 24.38% and 4.12%, respectively. Physiological and enzyme activity analyses indicated that HEER treatment-induced increase in hardness was associated with the phenylpropanoid metabolic pathway. Moreover, the HEER significantly down-regulated the expression of several key genes, namely FaPAL, FaC4H, and FaCAD. This study helps to deepen the understanding of the inhibition of lignification by HEER and provide new insights for the development of preservation technology of faba bean.

Comprehensive, Genome-Wide Identification and Expression Analyses of Phenylalanine Ammonia-Lyase Family under Abiotic Stresses in Brassica oleracea.

Phenylalanine ammonia-lyase (PAL) acts as the rate-limiting enzyme for anthocyanin biosynthesis through the phenylpropanoid pathway, a crucial component of plant secondary metabolism. The PAL gene family plays a crucial role in plants' defense and stress responses, but its in silico identification and expression analyses in Brassica oleracea under different abiotic stresses remain unexplored. In this study, nine BolPAL, seven BrPAL, four AtPAL, and seventeen BnPAL genes were obtained from the genomes of B. oleracea, Brassica rapa, Arabidopsis thaliana, and Brassica napus, respectively. Segmental duplication and purifying selection are the causes of the BolPAL gene's amplification and evolution. The BolPAL genes with comparable intron-exon architectures and motifs were grouped together in the same clade. Three categories comprised the cis-regulatory elements: abiotic stressors, phytohormones, and light. According to the results of the qRT-PCR experiments, the majority of the BolPAL genes were expressed highly under MeJA, a low temperature, and a high temperature, and they were downregulated under ABA. Under white light (100 µmol m-2 s-1) with 50, 100, or 150 µmol m-2 s-1 far-red (FR), only a small number of the PAL genes were expressed at 50 and 100 µmol m-2 s-1 FR, while the majority of the PAL genes were slightly elevated at 150 µmol m-2 s-1 FR. This work offers a theoretical foundation for molecular breeding research to investigate the role of BolPAL genes and their role in anthocyanin biosynthesis.

Prolonging Cyclamen Flower Vase Life via 8-HQS and AgNO3 Treatments in a Controlled Release System

The current study applied electrospun fibers containing 8-hydroxyquinoline-5-sulfonic acid (8-HQS) (100, 150, and 200 mg L−1) and silver nitrate (AgNO3) (15 and 20 mg L−1) to enhance the longevity and qualitative parameters of two cyclamen cultivars. The results indicated that the vase life of the flowers treated with 20 mg L−1 AgNO3 and 200 mg L−1 8-HQS was higher than that of the other treatments (16 days). Cyclamens treated with 8-HQS (100 mg L−1) + AgNO3 (15 mg L−1) and 8-HQS (100 mg L−1) + AgNO3 (20 mg L−1) had lower polyphenol oxidase (PPO) activity than the control group. Also, it was observed that the higher phenylalanine ammonia-lyase (PAL) enzyme activity of cyclamens in the 8-HQS (150 mg L−1) + AgNO3 (15 mg L−1) treatment was longer than that of the other treatments and control groups. Treatment with 100 mg L−1 8-HQS and 20 mg L−1 AgNO3 showed higher peroxidase (POD) activity than the different treatments. This research indicated that adding AgNO3 and 8-HQS to electrospun fibers is a promising method for enhancing the longevity and maintaining the quality of these cut flowers.

Regional propolis extracts suppress Fusarium fujikuroi and boost rice seedling growth and response against Bakanae disease

Bakanae, caused by Fusarium fujikuroi, is a serious seed-borne disease affecting rice production worldwide. Herein, we investigated the potential of propolis, a natural honeybee product, collected from three geographic locations in Egypt: North (Menofia), Middle (Cairo), and South (Sohag), and extracted with four different solvents (ethanol, olive oil, hexane, and water) as a sustainable eco-friendly alternative to control the Bakanae disease in rice. In vitro experiments showed that propolis extracts exhibited antifungal activity against F. fujikuroi and significantly suppressed its mycelial growth and sporulation. The antifungal activity of propolis extracts was associated with its chemical composition which varied depending on geographical origin, and the extraction solvents. Moreover, SEM-based analysis revealed that ethanolic extract of northern propolis prominently altered the microconidia morphology of F fujikuroi, which shrunken and seemed to lose their viability. These findings were further confirmed in vivo under greenhouse conditions. Soaking F fujikuroi-inoculated rice seeds in 1000 ppm of propolis extract significantly reduced the bakanae disease incidence, and disease severity index compared to mock-treated controls. Although infection with F fujikuroi induced the accumulation of H2O2, the application of propolis extracts alleviated oxidative stress and significantly reduced the H2O2 levels within infected rice seedlings. Moreover, propolis extracts enhanced the profile of enzymatic antioxidants (guaiacol-dependent peroxidase [POX] and polyphenol oxidase [PPO]) in F. fujikuroi-infected rice seedlings. Finally, Propolis extracts-treated rice seedlings exhibited higher transcript levels of three PTI-marker genes including nonexpressor of pathogenesis-related genes 1 (OsNPR1), WRKY transcription factor 21(OsWRKY21), and phenylalanine ammonia-lyase (OsPAL1), which are associated with systemic acquired resistance (SAR) and crucial for the plant's defense response against pathogens. Collectively, these findings suggest that propolis might be a promising sustainable, eco-friendly alternative to control bakanae disease and other fungal seed-borne phytopathogens due to its antifungal properties and ability to induce a complex multilayered defense system within infected plants.

Methyl salicylate induces endogenous jasmonic acid and salicylic acid in 'Nam Dok Mai' mango to maintain postharvest ripening and quality

Salicylic acid (SA) and jasmonic acid (JA) are indispensable phytohormones whose interaction influences the ripening process in plants. Methyl salicylate (MeSA) and methyl jasmonate (MeJA) have been utilized to elevate the endogenous levels of SA and JA in horticultural products after harvest. However, their ability to preserve mango is uncertain. Individually and combined effects of exogenous MeSA and MeJA on mango ripening quality were investigated. 'Nam Dok Mai' mangoes were fumigated with MeSA, MeJA, and MeSA plus MeJA (MeSAJA) prior to storage for 6 d at 25 °C and 80–85% relative humidity (RH). Fruit ripening attributes, respiration rate, ethylene (ET) production, total phenolics (TP), and malondialdehyde (MDA) were assessed. Endogenous SA and JA levels were measured, as were the activities of lipoxygenase (LOX) and phenylalanine ammonia-lyase (PAL), and the expression of related genes MiPAL, MiICS, and MiLOX. Individual application of MeSA or MeJA preserved the mango quality by reducing ET production, respiration rate, and MDA levels while raising TP shortly after treatment. The ripening quality mirrored the induced SA and JA levels and correlated with the high expression of biosynthetic-related genes (MiPAL, MiICS, and MiLOX). Individual treatments stimulated SA and JA biosynthesis, demonstrating that these phytohormones are functionally connected and interdependent. When combined, MeSAJA caused a tradeoff response and distinct phenotypic outcomes compared to the individual treatments. As a result, MeSA fumigation is a practical method for preserving mango quality after harvest.

Enzymatic Characterization of SpPAL Genes in S. polyrhiza and Overexpression of the SpPAL3.

Phenylalanine ammonia-lyase (PAL, EC 4.3.1.5) catalyzes the deamination of phenylalanine, which is the initial step in the biosynthesis of phenylpropanoids. It serves as a crucial enzyme that facilitates the transfer of carbon from primary to secondary metabolism in plants. Duckweed is regarded as a promising chassis plant in synthetic biology research and application, due to its being rich in secondary metabolites and other advantages. The genes encoding PAL in Spirodela polyrhiza (L.) Schleid, the giant duckweed, were investigated in this study. Three SpPAL genes (SpPAL1-SpPAL3) were identified and cloned. All of them were successfully expressed in E. coli, and their recombinant proteins all showed PAL activity. In addition, SpPAL1 and SpPAL2 proteins could also utilize tyrosine as substrate, although the activity was low. A qRT-PCR analysis demonstrated that the expression of SpPAL3 was most pronounced in young fronds. It was found that the expression of SpPAL1 and SpPAL3 was significantly induced by MeJA treatment. Overexpression of SpPAL3 in Lemna turionifera inhibited the growth of fronds and adventitious roots in the transgenic plants, indicating the importance of SpPAL3 in duckweed besides its involvement in the secondary metabolism.

Inoculation with Jeotgalicoccus sp. improves nutritional quality and biological value of Eruca sativa by enhancing amino acid and phenolic metabolism and increasing mineral uptake, unsaturated fatty acids, vitamins, and antioxidants.

Plant growth-promoting bacteria (PGPB) are considered a promising tool for triggering the synthesis of bioactive compounds in plants and to produce healthy foods. This study aimed to demonstrate the impact of PGPB on the growth, accumulation of primary and secondary metabolites, biological activities, and nutritional qualities of Eruca sativa (arugula), a key leafy vegetable worldwide. To this end, Jeotgalicoccus sp. (JW0823), was isolated and identified by using partial 16S rDNA-based identification and phylogenetic analysis. The findings revealed that JW0823 significantly boosted plant biomass production by about 45% (P<0.05) and enhanced pigment contents by 47.5% to 83.8%. JW0823-treated plants showed remarkable improvements in their proximate composition and vitamin contents, with vitamin E levels increasing by 161.5%. JW0823 induced the accumulation of bioactive metabolites including antioxidants, vitamins, unsaturated fatty acids, and essential amino acids, thereby improving the nutritional qualities of treated plants. An increase in the amounts of amino acids was recorded, with isoleucine showing the highest increase of 270.2%. This was accompanied by increased activity of the key enzymes involved in amino acid biosynthesis, including glutamine synthase, dihydrodipicolinate synthase, cystathionine γ-synthase, and phenylalanine ammonia-lyase enzymes. Consequently, the total antioxidant and antidiabetic activities of the inoculated plants were enhanced. Additionally, JW0823 improved antimicrobial activity against several pathogenic microorganisms. Overall, the JW0823 treatment is a highly promising method for enhancing the health-promoting properties and biological characteristics of E. sativa, making it a valuable tool for improving the quality of this important leafy vegetable.

Exogenous putrescine application imparts salt stress-induced oxidative stress tolerance via regulating antioxidant activity, potassium uptake, and abscisic acid to gibberellin ratio in Zinnia flowers

This research was conducted to investigate the efficacy of putrescine (PUT) treatment (0, 1, 2, and 4 mM) on improving morphophysiological and biochemical characteristics of Zinnia elegans “State Fair” flowers under salt stress (0, 50, and 100 mM NaCl). The experiment was designed in a factorial setting under completely randomized design with 4 replications. The results showed that by increasing the salt stress intensity, the stress index (SSI) increased while morphological traits such as plant height decreased. PUT treatments effectively recovered the decrease in plant height and flower quality compared to the not-treated plants. Treatment by PUT 2 mM under 50 and 100 mM salt stress levels reduced the SSI by 28 and 35%, respectively, and increased plant height by 20 and 27% compared to untreated plants (PUT 0 mM). 2 mM PUT treatment also had the greatest effect on increasing fresh and dry biomass, number and surface area of leaves, flower diameter, internodal length, leaf relative water content, protein contents, total chlorophyll contents, carotenoids, leaf potassium (K+) content, and K+/Na+ ratio in treated plants compared to untreated control plants. The treatment of 2 mM PUT decreased the electrolyte leakage, leaf sodium (Na+) content, H2O2, malondialdehyde, and proline content. Furthermore, PUT treatments increased the activity of defense-related enzymes including catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), and phenylalanine ammonium lyase (PAL), and reduced the abscisic acid (ABA) content while increased the level of gibberellin (GA) content compared to untreated samples under all different levels of salinity stress. In this research, enhancing the plant’s antioxidant system, increasing K+ absorption, K+/Na+ ratio, and reducing the ABA/GA ratio are likely the most important mechanisms of PUT treatment, which improved growth, and maintained the visual quality of zinnia flowers under salt stress conditions.

Effects of chitosan hydrolysate on control of postharvest infection caused by Botrytis cinerea and physiological responses of wounded tomato fruit

Chitosan is considered an eco-friendly plant protection agent. Chitosan hydrolysate (CH) with an average molecular weight (MW) of the main fraction of 135 × 103 Da, with a deacetylation degree (DD) of 93 % is an unfractionated product of nitric acid hydrolysis of high molecular weight chitosan. The effect of the CH on gray mold caused by Botrytis cinerea in tomato fruit stored at 25 °C was investigated. Chitosan provided effective control of B. cinerea on tomato fruit. The CH treatment of wounded tomato fruit had a protective effect, reducing the percentage of infected fruit on the 7 d after treatment to 50 %, compared with untreated wounded fruit (69 %) and water-treated fruit (88 %). The protective effect of the CH in tomato fruit may be due to a direct fungitoxic action against the pathogen. It was found that the CH induced an immune response in tomato fruit via the accumulation of phenolic compounds. The level of phenolic compounds in the CH group was higher than in the untreated wound group from day 1 to 5, with a maximum reached on day 3 (113 mg-eq GA kg-1). No significant differences were found in the activities of peroxidase, phenylalanine ammonia lyase, polyphenol oxidase, β-1,3-glucanase and chitinase. Thus, the CH affects the processes occurring during fruit damage and contributes to the preservation of the consumer qualities of fruit.

Zinc oxide nanoparticles reduce cadmium accumulation in hydroponic lettuce (Lactuca sativa L.) by increasing photosynthetic capacity and regulating phenylpropane metabolism

Due to the continuous production of industrial wastes and the excessive use of chemical fertilizers and pesticides, severe cadmium (Cd) pollution in soil has occurred globally. This study investigated the impacts of incorporating zinc oxide nanoparticles (ZnONPs) into hydroponically grown lettuce (Lactuca sativa) under cadmium stress conditions, to seek effective methods to minimize Cd buildup in green leafy vegetables. The results showed that 1 mg/L of Cd significantly inhibited lettuce growth, decreasing in leaves (29 %) and roots (33 %) biomass. However, when lettuce was exposed to 2.5 mg/L ZnONPs under cadmium stress, the growth, chlorophyll content, net photosynthetic rate (Pn), stomatal conductance (Gs), actual photochemical efficiency of PSII (φPSII), and activity of key enzymes in photosynthesis were all significantly enhanced. Furthermore, ZnONPs significantly decreased the accumulation of Cd in lettuce leaves (36 %) and roots (13 %). They altered the subcellular distribution and chemical morphology of Cd in lettuce by modifying the composition of cell walls (such as pectin content) and the levels of phenolic compounds, resulting in a reduction of 27 % in Cd translocation from roots to leaves. RNA sequencing yielded 45.9 × 107 and 53.4 × 107 clean reads from plant leaves and roots in control (T0), Cd (T1), Cd+ZnONPs (T2), and ZnONPs (T3) treatment groups respectively, and 3614 and 1873 differentially expressed genes (DEGs) were identified. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis identified photosynthesis, carbon fixation, and phenylpropanoid metabolism as the main causes of ZnONPs-mediated alleviation of Cd stress in lettuce. Specifically, the DEGs identified included 12 associated with photosystem I, 13 with photosystem II and 23 DEGs with the carbon fixation pathway of photosynthesis. Additionally, DEGs related to phenylalanine ammonia-lyase, caffeoyl CoA 3-O-methyltransferase, peroxidase, 4-coumarate-CoA ligase, hydroxycinnamoyl transferase, and cytochrome P450 proteins were also identified. Therefore, further research is recommended to elucidate the molecular mechanisms by which ZnONPs reduce Cd absorption in lettuce through phenolic acid components in the phenylpropanoid metabolism pathway. Overall, treatments with ZnONPs are recommended to effectively reduce Cd accumulation in the edible portion of lettuce.

Unraveling barley's PAL gene family: a genome-wide study on defense mechanisms against Puccinia graminis f. sp. tritici

Phenylalanine ammonia lyase (PAL) is a pivotal enzyme bridging primary and secondary phenylpropanoid metabolism, influencing plant growth, development, and stress responses. Despite extensive studies on PAL genes across various plant species, their investigation in barley, a critical staple food globally, has been relatively scarce. In this study, we have successfully identified 10 HvPAL genes, designated as HvPAL genes, in Hordeum vulgare (barley). These HvPAL genes were categorized based on their conserved sequences, which revealed patterns through MEME analysis and multiple sequence alignment. Interestingly, we found cis elements related to stress in the promoter regions of HvPAL genes, indicating their involvement in the response to pathogens. Furthermore, these gene promoters contained components associated with light, development, and hormone responsiveness. This suggests that they may play a role in hormonal developmental processes. MicroRNAs were also identified as regulators of the HvPAL genes we identified highlighting their significance in barley. To further investigate these gene expression patterns, we analyzed the RNA-seq data revealed the upregulating of HvPAL 2, HvPAL3, and HvPAL8, and downregulating HvPAL 5, HvPAL 6, and HvPAL9 genes in this study. This study focused on the regulation of PAL genes in response to 23 different races of Puccinia graminis f. sp. tritici in barley. These results suggest ways to improve traits and develop barley varieties that are resistant to pathogens by selectively increasing the expression of certain HvPAL genes that were not previously regulated. This thorough investigation aims to expand our knowledge of the versatility of the PAL gene family, providing insights for advancements in host -pathogen genetics.

Understanding the role of Bacillus subtilis GEB1 in enhancing guava plant immunity against Meloidogyne enterolobii: A multifaceted approach

Guava root-knot nematode, Meloidogyne enterolobii has emerged as a significant threat to guava cultivation, impacting production worldwide. By integrating the molecular, histopathological and in silico approaches the current study explores the efficacy of Bacillus subtilis GEB1 in enhancing the resistance of guava against M. enterolobii. The gene expression studies reveal that guava plants treated with B. subtilis and challenged with nematodes at 72 h showed 2 fold increase in phytoene synthase, 2.1 fold increase in mitogen-activated protein kinase, 1.54 fold increase in phenylalanine ammonia-lyase and 1.82 fold increase in peroxidase genes when compared to untreated control. The Scanning electron microscope analysis of guava roots treated with B. subtilis revealed the presence of spores in the rhizoplane region which led to deter the invading nematodes. The comparative histological studies with guava roots treated with B. subtilis revealed lesser damage in the cortex, vascular regions with limited hypertrophy and hyperplasia, lesser adult females, and feeding traces with minimum root, stele and cortex diameter and thickness than those of untreated infested roots. Attempts were made to dock the plant functional proteins with B. subtilis peptides to understand their interaction. The results revealed that bacillobactin showed a greater binding affinity of −9.0 kcal/mol with phytoene synthase, plipstatin (−16.0 kcal/mol), and fengycin (−15.9 kcal/mol) with MAPK proteins of guava. Overall, the current study offers insight into the intricate mechanisms of plant-nematode-bacteria interactions and underscores the importance of B. subtilis GEB-1 as a biocontrol agent to combat Meloidogyne enterolobii infection in guava.

Methyl jasmonate induced tolerance effect of Pinus koraiensis to Bursaphelenchus xylophilus.

Methyl jasmonate (MeJA) can affect the balance of hormones and regulate the disease resistance of plants. Exploring the application and mechanism of MeJA in inducing the tolerance of Pinus koraiensis to pine wood nematode (PWN) infection is of great significance for developing new strategies for pine wilt disease control. Different concentrations (0.1, 1, 5 and 10 mm) of MeJA treatment groups showed differences in relative tolerance index and relative anti-nematode index of P. koraiensis seedlings to PWN infection. The treatment of 5 mm MeJA solution induced the best tolerance effect, followed by the 1 mm MeJA solution. Transcriptome analysis indicated that many plant defense-related genes upregulated after treatment with 1, 5 and 10 mm MeJA solutions. Among them, genes such as jasmonate ZIM domain-containing protein, phenylalanine ammonia-lyase and peroxidase also continuously upregulated after PWN infection. Metabolome analysis indicated that jasmonic acid (JA) was significantly increased at 7 days postinoculation with PWN, and after treatment with both 1 and 5 mm MeJA solutions. Integrated analysis of transcriptome and metabolome indicated that differences in JA accumulation might lead to ubiquitin-mediated proteolysis, and expression changes in trans-caffeic acid and trans-cinnamic acid-related genes, leading to the abundance differences of these two metabolisms and the formation of multiple lignin and glucosides. MeJA treatment could activate the expression of defense-related genes that correlated with JA, regulate the abundance of defense-related secondary metabolites, and improve the tolerance of P. koraiensis seedlings to PWN infection. © 2024 Society of Chemical Industry.

The rice R2R3 MYB transcription factor FOUR LIPS connects brassinosteroid signaling to lignin deposition and leaf angle.

Leaf angle is an important agronomic trait for crop architecture and yield. In rice (Oryza sativa), the lamina joint is a unique structure connecting the leaf blade and sheath that determines leaf angle. Brassinosteroid (BR) signaling involving GLYCOGEN SYNTHASE KINASE-3 (GSK3)/SHAGGY-like kinases and BRASSINAZOLE-RESISTANT1 (BZR1) has a central role in regulating leaf angle in rice. In this study, we identified the atypical R2R3-MYB transcription factor FOUR LIPS (OsFLP), the rice homolog of Arabidopsis (Arabidopsis thaliana) AtFLP, as a participant in BR-regulated leaf angle formation. The spatiotemporal specificity of OsFLP expression in the lamina joint was closely associated with lignin deposition in vascular bundles and sclerenchyma cells. OsFLP mutation caused loose plant architecture with droopy flag leaves and hypersensitivity to BRs. OsBZR1 directly targeted OsFLP, and OsFLP transduced BR signals to lignin deposition in the lamina joint. Moreover, OsFLP promoted the transcription of the phenylalanine ammonia-lyase family genes OsPAL4 and OsPAL6. Intriguingly, OsFLP feedback regulated OsGSK1 transcription and OsBZR1 phosphorylation status. In addition, an Ala-to-Thr substitution within the OsFLP R3 helix-turn-helix domain, an equivalent mutation to that in Osflp-1, affected the DNA-binding ability and transcriptional activity of OsFLP. Our results reveal that OsFLP functions with OsGSK1 and OsBZR1 in BR signaling to maintain optimal leaf angle by modulating the lignin deposition in mechanical tissues of the lamina joint.

Genome-Wide Characterization and Expression Analysis of CsPALs in Cucumber (Cucumis sativus L.) Reveal Their Potential Roles in Abiotic Stress and Aphid Stress Tolerance.

Phenylalanine ammonia lyase (PAL) is a pivotal enzyme in the phenylalanine metabolic pathway in plants and has a crucial role in the plant's response to environmental stress. Although the PAL family has been widely studied in many plant species, limited is known about its particular role in cucumbers under stress. We investigated the physicochemical properties, gene structure, gene duplication events, conserved motifs, cis-acting elements, protein interaction networks, stress-related transcriptome data, and quantitatively validated key stress-related genes. The main results indicated that 15 PAL genes were grouped into four clades: I, II, and III when arranged in a phylogenetic tree of PAL genes in angiosperms. The analysis of the promoter sequence revealed the presence of multiple cis-acting elements related to hormones and stress responses in the cucumber PAL genes (CsPALs). The analysis of protein interaction networks suggested that CsPAL1 interacts with eight other members of the PAL family through CsELI5 and CsHISNA, and directly interacts with multiple proteins in the 4CL family. Further investigation into the expression patterns of CsPAL genes in different tissues and under various stress treatments (NaCl, Cu2+, Zn2+, PEG6000, aphids) demonstrated significant differential expression of CsPALs across cucumber tissues. In summary, our characterization of the CsPAL family offers valuable insights and provides important clues regarding the molecular mechanisms of CsPALs in managing abiotic and biotic stress interactions in cucumbers.

Combined application of the endophyte Bacillus K1 and sodium dehydroacetate alleviates postharvest gray mold in grapes

Botrytis cinerea, which causes postharvest gray mold, is a primary pathogen that limits grape shelf-life and consumption and causes substantial yield loss worldwide. The combined use of biocontrol agents and food additives has attracted increasing interest. The effects of combined treatment with the endophyte Bacillus subtilis K1 and sodium dehydroacetate (SD) on the occurrence of gray mold and maintenance of grape fruit quality were studied. Treatment with a K1 suspension (1 × 108 CFU/ml) combined with 0.32 g/L SD resulted in markedly improved control of B. cinerea on grapes. The disease incidence and severity in the groups treated with K1 alone or in combination with SD were significantly lower than those in the control groups (P < 0.05) when the mixtures were applied 2 h after pathogen inoculation. Moreover, application of the mixture could maintain the appearance, firmness, total soluble solid (TSS) content and titratable acidity (TA) of grape fruit. Furthermore, the combination triggered increases in the activities of defense-related enzymes such as peroxidase (POD), phenylalanine ammonia lyase (PAL), catalase (CAT), superoxide dismutase (SOD) and polyphenol oxidase (PPO). Additionally, it could increase the vitamin C content. Thus, appropriate combinations of biocontrol agents and chemical reagents can provide effective protection against postharvest decay.