Phenylalanine Ammonia-lyase Activity Research Articles

Multi-frequency thermosonication washing treatments of fresh-cut lotus root: Effect on the accumulation of phenolics and storage quality characterization evaluation

The effects of thermosonication (TS) washing at varying multi-frequencies in comparison to ultrasonication (US) and water washing (as a control) on the fresh-cut lotus root phenolics accumulation and the storage quality characteristics were explored. The relationships between free phenols (FPs), bound phenols (BPs), total phenolic content (TPC), and total antioxidant capacity were also revealed. Thermosonication increased the free phenols and total phenolic content, with the thermosonication of 20 + 40 + 60 kHz showing the most significant effect, and TS predominantly improved the total antioxidant capacity. Thermosonication promoted phenylalanine ammonia-lyase (PAL) activity and inhibited polyphenol peroxidase (POD) activity. The color analysis showed the thermosonicated samples exhibited the lowest value of ΔE and the browning degree. Thermosonication substantially increased weight loss and firmness, while reducing the levels of malondialdehyde (MDA) and Vitamin C (VC) compared to control. Overall, TS washing can increase the phenolic content of fresh-cut lotus root while preserving its antioxidant capacity and qualitative characteristics.

Carbon Dot-Mediated Photodynamic Treatment Improves the Quality Attributes of Post-Harvest Goji Berries (Lycium barbarum L.) via Regulating the Antioxidant System.

Carbon dots (CDs) have been proposed as photosensitizers in photodynamic treatment (PDT), owing to their excellent biological attributes and budding fruit preservation applications. In the present study, CDs (4.66 nm) were synthesized for photodynamic treatment to improve the quality attributes in post-harvest goji berries. The prepared CDs extended the storage time of the post-harvest goji berries by 9 d. The CD-mediated PDT postponed the hardness and decay index loss, reduced the formation of malondialdehyde (MDA), hydrogen peroxide (H2O2), and superoxide anion (O2•-) significantly, and delayed the loss of vital nutrients like the total protein, phenols, and flavonoids. The CD-mediated PDT improved the catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD), phenylalanine ammonia-lyase (PAL), glutathione reductase (GR), and superoxide dismutase (SOD) activities, but did not improve polyphenol oxidase (PPO) activity. In addition, The CD-mediated PDT induced the accumulation of ascorbic acid (ASA) and glutathione (GSH). Overall, a CD-mediated PDT could extend the storage time and augment the quality attributes in post-harvest fresh goji berries by regulating the antioxidant system.

Widely targeted metabolomics analysis reveals the potential metabolic network of high-pressure carbon dioxide regulating fresh-cut Chinese water chestnut yellowing

In this study, we applied widely targeted metabolomics and physiological analysis to investigate the non-volatile metabolites changes and regulatory mechanisms of high-pressure carbon dioxide (HPCD) treatment on the yellowing of fresh-cut Chinese water chestnut (CWC). A total of 349 non-volatile metabolites were identified and subjected to principal component analysis (PCA), OPLS-DA and KEGG enrichment analysis. The results showed that the yellowing of fresh-cut CWC was related to membrane lipid metabolism and flavonoid biosynthesis. Damage stress induced membrane lipid metabolism and flavonoid biosynthesis in surface tissues, and the increase of phenylalanine ammonia-lyase (PAL) activity in flavonoid biosynthesis might be triggered by signaling molecules from membrane lipid metabolism. On the one hand, HPCD treatment could directly inhibit the activity of PAL, and reduce the biosynthesis of flavonoids in the damaged tissues. On the other hand, HPCD could indirectly inhibit the generation and accumulation of potential signaling molecules by regulating membrane lipid metabolism, thus preventing signaling molecules from triggering flavonoid biosynthesis. This study proposed a potential network of HPCD regulating the yellowing of fresh-cut CWC and established the foundation for further control of yellowing in fresh-cut CWC.

Nanofertilizers and plant metabolites: Investigating their influence on trophic interactions in the cucumber-melon aphid-green lacewing

The role of fertilizers in increasing nutritional content and making host plants more attractive to herbivores has been repeatedly proved. This study investigated the effect of applying three levels of nano-chelated fertilizer (vegetables and summer crops specific fertilizer) (2, 3, and 4 kg/ha) on the levels of malondialdehyde (MDA), and phenylalanine ammonia-lyase (PAL), peroxidase (POD), polyphenol oxidase (PPO), catalase (CAT), ascorbic acid (ASA), flavonoid, and phenolic compounds in cucumber plant (Cucumis sativus L.). Additionally, the research surveyed the influence of fertilization and cucumber metabolite compounds on the life history of Aphis gossypii (Glover) (Hemiptera: Aphididae) and Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) in a tri-trophic context. Host plant content analysis showed that biotic stress resulting from the aphid infestation in cucumber plants increased the POD, PPO, CAT activity, and MDA contents. However, it decreased PAL activity, flavonoid, and phenol contents in the control treatment and 2, 3, and 4 kg/ha of nano-chelated fertilizer levels. Moreover, plant fertilization increased the herbivore population growth rates and decreased the predator population growth rates by affecting the nutritional contents and quality of the host plant. Accordingly, the aphid's intrinsic rate of increase (r) was ranged from 0.319 to 0.365 day−1. While finite rate of increase (λ) was estimated as 1.376 to 1.441 day−1 on control to 2 kg/ha nano-chelated fertilizer treatment. In addition, the intrinsic rate of increase of C. carnea was 0.116 to 0.131 and the finite rate of increase was 1.123 to 1.139 day−1 on 2 kg/ha nano-chelated fertilizer and control treatments, respectively. The maximum and minimum net reproductive rate (R0) values of the aphid were recorded on 3 kg/ha nano-chelated fertilizer and control treatments as 46.34 and 37.18 offsprings, respectively, whilst these values ranged from 145.51 on 2 kg/ha to 196.93 offsprings on 4 kg/ha regimes for the green lacewing. Notably, the utilization of 2, 3, and 4 kg/ha of nano-chelated fertilizer promotes cucumber defensive metabolites compounds such as PAL, POD, CAT, flavonoid, and ASA and induces the plant's resistance to melon aphids directly. It can be concluded that the utilization of nano-chelated fertilizer potentially can enhance cucumber plant resistance to A. gossypii by improving the antioxidant metabolite compounds, and be an effective part of integrated pest management programs.

Sound waves alter the viability of tobacco cells via changes in cytosolic calcium, membrane integrity, and cell wall composition.

The effect of sound waves (SWs) on plant cells can be considered as important as other mechanical stimuli like touch, wind, rain, and gravity, causing certain responses associated with the downstream signaling pathways on the whole plant. The objective of the present study was to elucidate the response of suspension-cultured tobacco cells (Nicotiana tabacum L. cv Burley 21) to SW at different intensities. The sinusoidal SW (1,000 Hz) was produced through a signal generator, amplified, and beamed to the one layer floating tobacco cells inside a soundproof chamber at intensities of 60, 75, and 90 dB at the plate level for 15, 30, 45, and 60 min. Calibration of the applied SW intensities, accuracy, and uniformity of SW was performed by a sound level meter, and the cells were treated. The effect of SW on tobacco cells was monitored by quantitation of cytosolic calcium, redox status, membrane integrity, wall components, and the activity of wall modifying enzymes. Cytosolic calcium ions increased as a function of sound intensity with a maximum level of 90 dB. Exposure to 90 dB was also accompanied by a significant increase of H2O2 and membrane lipid peroxidation rate but the reduction of total antioxidant and radical scavenging capacities. The increase of wall rigidity in these cells was attributed to an increase in wall-bound phenolic acids and lignin and the activities of phenylalanine ammonia-lyase and covalently bound peroxidase. In comparison, in 60- and 75 dB, radical scavenging capacity increased, and the activity of wall stiffening enzymes reduced, but cell viability showed no changes. The outcome of the current study reveals that the impact of SW on plant cells is started by an increase in cytosolic calcium. However, upon calcium signaling, downstream events, including alteration of H2O2 and cell redox status and the activities of wall modifying enzymes, determined the extent of SW effects on tobacco cells.

Effects of 1-methylcyclopropene on skin greasiness and quality of 'Yuluxiang’ pear during storage at 20°C

During storage at 20°C, specific pear cultivars may exhibit a greasy texture and decline in quality due to fruit senescence. Among these varieties, 'Yuluxiang’ is particularly susceptible to peel greasiness, resulting in significant economic losses. Therefore, there is an urgent need for a preservative that can effectively inhibit the development of greasiness. Previous studies have demonstrated the efficacy of 1-methylcyclopropene (1-MCP) in extending the storage period of fruits. We hypothesize that it may also influence the occurrence of postharvest peel greasiness in the 'Yuluxiang’ pears. In this study, we treated 'Yuluxiang’ pears with 1-MCP. We stored them at 20°C while analyzing the composition and morphology of the surface waxes, recording enzyme activities related to wax synthesis, and measuring indicators associated with fruit storage quality and physiological characteristics. The results demonstrate that prolonged storage at 20°C leads to a rapid increase in skin greasiness, consistent with the observed elevations in L*, greasiness score, and the content of total wax and greasy wax components. Moreover, there were indications that cuticular waxes underwent melting, resulting in the formation of an amorphous structure. In comparison to controls, the application of 1-MCP significantly inhibited increments in L* values as well as grease scores while also reducing accumulation rates for oily waxes throughout most stages over its shelf period, additionally delaying transitions from flaky-wax structures towards their amorphous counterparts. During the initial 7 d of storage, several enzymes involved in the biosynthesis and metabolism of greasy wax components, including lipoxygenase (LOX), phospholipase D (PLD), and β-ketoacyl-CoA synthase (KCS), exhibited an increase followed by a subsequent decline. The activity of LOX during early shelf life (0–7 d) and the KCS activity during middle to late shelf life (14–21 d) were significantly suppressed by 1-MCP. Additionally, 1-MCP effectively maintained firmness, total soluble solid (TSS) and titratable acid (TA) contents, peroxidase (POD), and phenylalanine ammonia-lyase (PAL) activities while inhibiting vitamin C degradation and weight loss. Furthermore, it restrained polyphenol oxidase (PPO) activity, ethylene production, and respiration rate increase. These findings demonstrate that 1-MCP not only delays the onset of peel greasiness but also preserves the overall storage quality of 'Yuluxiang’ pear at a temperature of 20°C. This study presents a novel approach for developing new preservatives to inhibit pear fruit peel greasiness and provides a theoretical foundation for further research on pear fruit preservation.

Combination of Sodium Nitroprusside and Controlled Atmosphere Maintains Postharvest Quality of Chestnuts through Enhancement of Antioxidant Capacity.

The purpose of this study was to clarify the effect of CA (controlled atmosphere, 2-3% O2 + 3% CO2) and NO (nitric oxide, generated by 0.4 nM sodium nitroprusside), alone or combined (CA + NO), on the physio-chemical properties, enzyme activities and antioxidant capacities of chestnuts during storage at 0 °C for 180 d. Compared with control (CT), CA and CA+NO both improved the storage quality of the samples, but only CA resulted in more ethanol production. Moreover, these improvements were further enhanced and ethanol synthesis was inhibited by the addition of NO. A spectrometer was used to assess the production of phenolic content (TPC) and activities of phenylalanine ammonia-lyase (PAL), superoxide dismutas (SOD), peroxidase (POD), catalase (CAT) and polyphenol oxidase (PPO) as influenced by CA or CA+NO treatments. Higher TPC, PAL, SOD, POD, CAT, and lower PPO were observed in CA alone, and more so in the combination with NO group. The increased antioxidant production and enhanced antioxidant activities contributed to scavenging reactive oxygen species (ROS) and reducing malondialdehyde (MDA). This study unveiled the correlations and differences between the effects of CA and CA+NO on storage quality, providing valuable insights into postharvest preservation and suggesting that the combination (CA+NO) was more beneficial for quality maintenance in chestnuts.

Overexpression of AtMYB12 transcription factor simultaneously enhances quercetin-dependent metabolites in radish callus

The study aimed to enhance quercetin production in radish by optimizing Agrobacterium tumefaciens-mediated in-planta transformation. This protocol involved infecting radish seed embryo axis with A. tumefaciens EHA105 strain carrying the 35S::AtMYB12. Radish seeds were infected with the Agrobacterium suspension (0.8 OD600) for 30 min, followed by sonication for 60 s and vacuum infiltration for 90 s at 100 mm Hg. A 3-day co-cultivation in Murashige and Skoog medium with 150 μM acetosyringone yielded a transformation efficiency of 59.6% and a transgenic callus induction rate of 32.3%. Transgenic plant and callus lines were confirmed by GUS histochemical assay, PCR, and qRT-PCR. The transgenic lines showed an increased expression of flavonoid pathway genes (AtMYB12, CHS, F3H, and FLS) and antioxidant genes (GPX, APX, CAT, and SOD) compared to WT plants. Overexpression of AtMYB12 in transgenic callus increased enzyme activity of phenylalanine ammonia lyase, catalase, and ascorbate peroxidase. In half-strength MS medium with 116.8 mM sucrose, the highest growth index (7.63) was achieved after 20 days. In AtMYB12 overexpressed callus lines, phenolic content (357.31 mg g−1 dry weight), flavonoid content (463 mg g−1 dry weight), and quercetin content (48.24 mg g−1 dry weight) increased significantly by 9.41-fold. Micro-wounding, sonication, and vacuum infiltration improved in-planta transformation in radishes. These high-quercetin-content transgenic callus lines hold promise as valuable sources of flavonoids.

Phenylalanine Ammonia-Lyase-Mediated Differential Response of Tomato (Solanum lycopersicum L.) Cultivars with Different Stress Tolerance to Treatment with Low-Molecular-Weight Chitosan

The latest research has shown that chitosan acts as a growth stimulator and elicitor in plants, including resistance to biotic and abiotic factors. However, increasing concentrations could possibly make chitosan a source of stress for plants. In this study, we investigated the effect of low-molecular-weight chitosan hydrolysate on the root development of tomato (Solanum lycoperscum) cultivars Red Cherry, Lel, and Tytan. The growth rate change, together with total phenolic content, phenylalanine ammonia-lyase (PAL) activity, and gene expression, were studied in relation to tomatoes. High concentrations of chitosan negatively affect the growth of tomato seedlings and contribute to changes in the tropism of the seedling roots. After the addition of chitosan hydrolysate, the PAL activity and the total phenolic content decreased 24 h later. PAL is a key enzyme in the biosynthesis of many plant stress factors. An analysis of the tomato PAL gene family was carried out. The SlPAL gene expression in the seedlings of cv. Cherry increased 1.5 times after 48 h, while in cv. Lel, the expression stably decreased in the presence of chitosan. The obtained results are supposed to aid our understanding of the mechanisms underlying the effects of chitosan on plant development and further its successful application in agriculture as well as in research on plant stress.

Evaluation of Resistance Resources and Analysis of Resistance Mechanisms of Maize to Stalk Rot Caused by Fusarium graminearum.

Stalk rot is one of the most destructive and widely distributed diseases in maize plants worldwide. Research on the performance and resistance mechanisms of maize against stem rot is constantly improving. In this study, among 120 inbred maize lines infected by Fusarium graminearum using the injection method, 4 lines (3.33%) were highly resistant to stalk rot, 28 lines (23.33%) were resistant, 57 lines (47.50%) were susceptible, and 31 lines (25.84%) were highly susceptible. The inbred lines 18N10118 and 18N10370 were the most resistant and susceptible with disease indices of 7.5 and 75.6, respectively. Treatment of resistant and susceptible maize inbred seedlings with F. graminearum showed that root hair growth of the susceptible inbred lines was significantly inhibited, and a large number of hyphae attached and adsorbed multiple conidia near the root system. However, the resistant inbred lines were delayed and inconspicuous, with only a few hyphae and spores appearing near the root system. Compared with susceptible inbred lines, resistant maize inbred line seedlings treated with F. graminearum exhibited elevated activities of catalase, phenylalanine ammonia-lyase, polyphenol oxidase, and superoxide dismutase. We identified 153 genes related to disease resistance by transcriptome analysis. The mitogen-activated protein kinase signaling and peroxisome pathways mainly regulated the resistance mechanism of maize inbred lines to F. graminearum infection. These two pathways might play an important role in the disease resistance mechanism, and the function of genes in the two pathways must be further studied, which might provide a theoretical basis for further understanding the molecular resistance mechanism of stalk rot and resistance gene mining.

Salt stress influences the proliferation of Fusarium solani and enhances the severity of wilt disease in potato

Soil salinity has emerged as a critical abiotic stress in potato production, whereas wilt disease, caused by Fusarium solani, is the significant biotic stress. An experiment was performed to decipher the occurrence of wilt incidence by F. solani FJ1 under the influence of salinity in both in vitroand pot culture conditions. High salt concentration negatively influenced root and shoot development in the variety “Kufri Jyoti” but positively affected the mycelial growth and sporulation behaviours of F. solani FJ1. There was abundant whitish mycelial growth with enhanced biomass and high sporulation (microconidia production) in F. solani FJ1 cultured on salt-supplemented media. Moreover, under high salinity conditions (EC 2–8 dS m−1), severe wilting and rotting of vascular bundles were observed in plants artificially inoculated with F. solani FJ1. The mortality rate of potato plants was significantly higher under individual and combined stresses as compared to control. The wilt index of individual and combined stressed plants was also substantially higher compared to the control. Additionally, compared to the control, there was a significant decrease in total chlorophyll content and membrane stability index of the leaves under combined stress. However, the total phenols were increased under stress conditions. The total sugar content of potato plants decreased in infected plants, but increased when exposed to salt stress or a combination of salt stress and pathogen infection. F. solani infection also increased the activity of peroxidase (POX) and decreased the activity of phenylalanine ammonia-lyase (PAL) and catalase (CAT). These results suggest that Fusarium wilt and dry rot will be a more severe disease for potato cultivation in saline soils.

Selenium nanoparticles conferred drought tolerance in tomato plants by altering the transcription pattern of microRNA-172 (miR-172), bZIP, and CRTISO genes, upregulating the antioxidant system, and stimulating secondary metabolism.

Drought stress is one of the major limiting factors for the production of tomato in Iran. In this study, the efficiency of selenate and Se nanoparticle (SeNP) foliar application on tomato plants was assessed to vestigate mitigating the risk associated with water-deficit conditions. Tomato plants were treated with SeNPs at the concentrations of 0 and 4mg L-1; after the third sprays, the plants were exposed to water-deficit conditions. The foliar spraying with SeNPs not only improved growth, yield, and developmental switch to the flowering phase but also noticeably mitigated the detrimental risk associated with the water-deficit conditions. Gene expression experiments showed a slight increase in expression of microRNA-172 (miR-172) in the SeNP-treated plants in normal irrigation, whereas miR-172 displayed a downregulation trend in response to drought stress. The bZIP transcription factor and CRTISO genes were upregulated following the SeNP and drought treatments. Drought stress significantly increased the H2O2 accumulation that is mitigated with SeNPs. The foliar spraying with Se or SeNPs shared a similar trend to alleviate the negative effect of drought stress on the membrane integrity. The applied supplements also conferred drought tolerance through noticeable improvements in the non-enzymatic (ascorbate and glutathione) and enzymatic (catalase and peroxidase) antioxidants. The SeNP-mediated improvement in drought stress tolerance correlated significantly with increases in the activity of phenylalanine ammonia-lyase, proline, non-protein thiols, and flavonoid concentrations. SeNPs also improved the fruit quality regarding K, Mg, Fe, and Se concentrations. It was concluded that foliar spraying with SeNPs could mitigate the detrimental risk associated with the water-deficit conditions.

Oligogalacturonides reduced postharvest losses by alleviating mechanical damage in Goji berry (Lycium barbarum Miller)

Goji berry (Lycium barbarum) is a typical berry with a tender and thin pericarp, high moisture content and hollow interior, making it highly susceptible to mechanical damage caused by harvest and transportation. As a consequence, this susceptibility results in considerable economic losses within the fresh produce industry due to the degradation of fruit quality and subsequent decay. Here, oligogalacturonides (OGs), a well-characterized plant damage-associated molecular pattern, were applied to reduce postharvest loss and extend the shelf life of berries of the goji cultivar NingQi1. The loss rate in the OGs treatment was 44.45 % lower than that in the 0.8 mm compression treatments on Day 6, and the OGs treatment also effectively inhibited softening and delayed weight loss. The activity of superoxide dismutase increased by 27.4 % on the 4th day after OGs treatment, accompanied by a decrease in malondialdehyde content ranging from 14.2 % to 24.8 % on days 2 to 4 compared to the control group. Furthermore, the phenylalanine ammonia-lyase activity of OGs-treated goji berries was 57.0 % higher than that of the control at 6th days, which slowed the reduction in secondary metabolites such as total flavonoids. The findings of this study indicated that OGs may reduce postharvest losses caused by mechanical damage, extend the shelf life of goji berry by reducing softening and weight loss, and reduce wounding injury by minimizing free radical form of reactive oxygen species.

Proper doses of brassinolide enhance somatic embryogenesis in different competent Korean pine cell lines during embryogenic callus differentiation.

Somatic embryogenesis of Korean pine (Pinus koraiensis Sieb. Et Zucc.), an ecologically and econimically very important conifer species, was hindered by the gradually weakens and fast runaway of the embryogenicity and embryo competence of the embryogenic callus. Brassinolide (BL) has shown the enhancing capability of somatic embryo regeneration. For checking the function of BL in this issue, we applied different concentrations of BL to Korean pine callus materials exhibiting different embryogenic capacities and subsequently monitored the physiological alterations and hormone dynamics of the embryogenic callus. Our study revealed that calli with different embryogenic strengths responded differently to different concentrations of BL, but the effect after the addition of BL was very uniform. The addition of BL during the proliferation phase of embryogenic callus may help to stimulate the biological activity of callus during the proliferation process and improve the level of cell metabolism, which is accompanied by a reduction in storage substances. BL could reduce the level of endogenous auxin IAA in embryogenic callus and increase the level of abscisic acid to regulate cell division and differentiation. In addition, the MDA content in the callus was significantly decreased and the activity of antioxidant enzymes was significantly increased after the addition of BL. During the proliferation of embryogenic callus, BL was added to participate in the metabolism of phenylpropane in the cells and to increase the activity of phenylalanine ammonia-lyase and the content of lignin in the cells. We deduced that the proper doses of BL for Korean pine embryogenic callus culture were as follow: calli with low, high and decreasing embryogenicity were subcultured after the addition of 0.75 mg/L, 0.35 mg/L, 2.00 mg/L BL, respectively, during proliferation culture stage.

Modulatory role of nitric oxide in wound healing of potato tubers

IntroductionWounding of potato (Solanum tuberosum L.) tubers affects the postharvest storage qualities and marketability. To mitigate wound-related losses, it is necessary to accelerate wound healing (WH) responses of potato tubers. While role of nitric oxide (NO) in healing of wounded biological tissues is well known, its impact on WH responses of potato tubers has not been examined thoroughly. The aim of this study was to elucidate the potential modulatory role of NO in WH response of potato tubers by determining the activity of key enzymes associated with NO biosynthesis.MethodsUsing a model wounding system, tuber tissue discs were extracted from mini tubers of cv. Russet Burbank to examine their WH responses. Tuber discs were treated with NO related chemicals, such as NO scavenger, nitric oxide synthase (NOS) inhibitor, and NO donors. The effect of these treatments on in vitro production of NO, activity of nitrate reductase, NOS, and phenylalanine ammonia-lyase were determined. The accumulation of suberin polyphenolics (SPP) in wounded parenchyma cells, an indicator of early suberization process, was analyzed histologically.ResultsTreatment of tuber tissues with the higher dose of an NO scavenger (2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide) at the time of wounding completely ceased SPP accumulation between 0 h to 3 d after wounding. Increased production of NO and enhanced activity of NOS were also observed immediately after wounding of the tuber tissues. The results suggest that NO is a key biological modulator in WH responses of potato tubers and could be optimized as a potential exogenous treatment to counter wound-related losses.

Endogenous compound chenodeoxycholic acid in potatoes can delay enzymatic browning by inducing antioxidant capacity

Enzymatic browning is a primary factor affecting the quality of fresh-cut potatoes. Our previous research demonstrated that warming the tubers after cold storage can alleviate the enzymatic browning of fresh-cut potatoes. In this research, we explored if some new endogenous compounds play roles in browning inhibitory effects. Utilizing a non-targeted metabolomics approach on tubers subjected to pre-cutting different temperature treatments, thirteen differential metabolites in potatoes were revealed, and five compounds with anti-browning effects were screened out. Among these five compounds, chenodeoxycholic acid (CDCA) exhibited the best inhibitory effect on browning and has not been reported in plants till now. The changes in CDCA content in tubers of pre-cutting different temperature treatments were further confirmed by LC-MS/MS. Subsequent experiments showed that the anti-browning effect of pre-cutting CDCA treatment was much better than post-cutting. Pre-cutting CDCA treatment only at a low concentration of 5 mg L−1 for a 10 min soaking and then standing for 6 h extended the shelf life of fresh potato slices to 5 d from less than 1 d of control. Not a big difference in polyphenol oxidase (PPO) activity and tyrosine contents were caused by pre-cutting CDCA treatment compared with control. However, pre-cutting CDCA treatment caused a notable reduction in the contents of malondialdehyde (MDA), superoxide anion (O2-), H2O2, and lipoxygenase (LOX) activity, and elevated the activities of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX). Meanwhile, CDCA suppressed phenylalanine ammonia-lyase (PAL) activity and reduced the contents of both individual and total phenolic compounds. These results suggest that CDCA, an endogenous compound in potato tuber, can improve the anti-browning ability of fresh-cut potatoes mainly by inducing the enhancement of antioxidant capacity.

Zinc and copper toxicity in basil (Ocimum basilicum L.) seedlings: Role of melatonin in mitigating stress

The effects of melatonin (MT) on the growth and antioxidant responses of basil (Ocimum basilicum L.) exposed to copper and zinc excess stress are investigated. For this purpose, seedlings were exposed to different concentrations of copper oxide (0, 50 and 150 µM), zinc oxide (0, 50 and 100 µM) and melatonin (0 and 100 µM) for 14 days. Growth and biochemical parameters, the activity of some antioxidant enzymes, and phenylalanine ammonia lyase (PAL) and some of the main nutritional elements in the shoot and root of seedlings were measured. The results of this study showed that the excess of copper (Cu 50 and 150 µM) and zinc (Zn 50 and 100 µM) causes a decrease in growth, and a higher oxidative stress indicator such as hydrogen peroxide and malondialdehyde (MDA) content. The homeostasis balance of mineral nutrition of basil seedlings was also disrupted under copper and zinc stress. Melatonin treatment in Cu, Zn stressed seedlings improved growth parameters by reducing the levels of hydrogen peroxide (H2O2) and malondialdehyde (MDA) and increasing the activity of PAL and antioxidant enzymes. Melatonin also regulated the distribution of minerals in basil seedlings under Cu and Zn stress conditions. The results of this research showed that MT can improve the tolerance of basil seedlings against copper and zinc stress by modulate growth and antioxidant responses and regulating mineral nutrition.

Influence of myoinositol on post-ripening and softening of Prunus salicina ‘Wushan plum’

To investigate the impact of myoinositol (MI) immersion treatment on the storage characteristics of Prunus salicina ‘Wushan Plum’, we assessed myoinositol content, ascorbic acid content, weight loss, decay rate, alteration in color, titratable acidity (TA), soluble solids (TSS), firmness, cell wall metabolism-related compounds, enzyme activities, and levels of gene expression throughout a 15-day storage period at 25 °C. The results revealed that MI treatment could increase myoinositol and ascorbic acid contents of fruit during the pre-storage period, effectively delay the color transformation and decay progression of P. salicina ‘Wushan Plum’ while maintaining elevated levels of TA and TSS. Furthermore, it suppressed the increase in weight loss and the decline in firmness. Notably, the delay in softening was more pronounced in the group treated with 100 mg L−1 MI compared to other groups. MI treatment regulated the expression levels of various genes associated with cell wall metabolism, which resulted in reduced activities of polygalacturonase (PG), pectate lyase (PL), pectin methylesterase (PME), cellulase (Cx), and β-glucosidase (β-Glu), and increased activities of phenylalanine ammonia-lyase (PAL) and cinnamyl alcohol dehydrogenase (CAD). Furthermore, MI treatment maintained higher levels of covalently bound pectin (CSP), cellulose, and lignin, while decreasing the levels of water-soluble pectin (WSP) in the fruit. As a result, MI treatment could delay the depolymerization of cell wall polysaccharides and further delay the quality deterioration of P. salicina ‘Wushan Plum’ fruits under ambient storage environment and prolong the storage period.

Methyl jasmonate improves resistance in scab-susceptible Red Delicious apple by altering ROS homeostasis and enhancing phenylpropanoid biosynthesis

Apple (Malus domestica) is an economically important rosaceous fruit crop grown at temperate climate zones. Nevertheless, its production is severely affected by scab disease caused by the ascomycetous fungus Venturia inaequalis (VI). Methyl jasmonate (MeJA) is a stress induced plant hormone, shown to induce resistance against wide range of pathogens. The current study investigated the role of MeJA in promoting scab tolerance in susceptible apple varieties through exogenous application of optimized (100 μM) MeJA concentration, followed by VI infection. According to our analysis, applying MeJA exogenously onto leaf surfaces resulted in increased membrane stability and decreased malondialdehyde levels in Red Delicious, suggesting that MeJA is capable of protecting tissues against oxidative damage through its role in restoring membrane stability. In addition, the changes in the levels of key antioxidative enzymes and reactive oxygen species (ROS) showed that exogenous MeJA maintains ROS homeostasis as well. Higher phenylalanine ammonia-lyase activity and increased accumulation of phenylpropanoids in MeJA-treated VI-infected plants indicated the MeJA reprogrammed phenylpropanoid biosynthesis pathway for scab tolerance. Our study of scab tolerance in apples induced by MeJA provides new insights into its physiological and biochemical mechanisms.

Investigation of the antibacterial activity of benziothiazolinone against Xanthomonas oryzae pv. oryzae

Plant pathogenic bacteria can cause numerous diseases for higher plants and result in severe reduction of crop yield. Introduction of new bactericides can always effectively control these plant diseases. Benziothiazolinone (BIT) is a novel fungicide registered in China for the control of plant fungal diseases, however, its anti-bacterial activity is not well studied. The results of activity tests showed that BIT exhibited stronger inhibitory activity against bacteria, particularly for Xanthomonas oryzae pv. oryzae (Xoo) (EC50 = 0.17 μg/mL), which was superior than that of the tested fungi in vitro. BIT also exhibited excellent protective and curative activity against rice bacterial leaf blight (BLB) caused by Xoo with the control efficacies of 71.37% and 91.64% at 600 μg/mL, respectively. After treatment with BIT, Xoo cell surface became wrinkled and the cell shape was distorted with extruding cellular content. It was also found that BIT decreased DNA synthesis and affected the biofilm formation and motility of Xoo cells. However, no significant change in the protein content was observed. Moreover, the results of quantitative real-time PCR also showed that expressions of several genes related to DNA synthesis, biofilm formation and motility of Xoo cells were down- or up-regulated, which further proved the anti-bacterial activity of BIT in influencing the biological properties of Xoo. Additionally, BIT also enhanced the activity of phenylalanine ammonia lyase (PAL), a plant defense enzyme. Taken together, benziothiazolinone might be served as an alternative candidate for the control of BLB.