Cinnamyl Alcohol Dehydrogenase Activity Research Articles

Host Plants and Fertilization Mediated Life History of American Serpentine Leaf Miner, Liriomyza trifolii (Burgess) (Diptera: Agromyzidae).

Herbivorous insects depend on the host plant to optimize their overall reproductive success, and balanced fertilization may alter the plant's quality against herbivory. Life history traits of the Liriomyza trifolii (Burgess) were determined under laboratory conditions using either unfertilized and fertilized plants of bean [Phaseolus vulgaris L. (Fabaceae)], chrysanthemum [Chrysanthemum × morifolium (Asteraceae)], potato [Solanum tuberosum (Solanaceae)], bell pepper [Capsicum annuum (Solanaceae)], and tomato [Solanum lycopersicum (Solanaceae)]. Results indicated that L. trifolii completed development on all studied unfertilized and fertilized plants. Nevertheless, a higher performance of the leaf miner was observed on bean and bell pepper plants compared to the other plants. Furthermore, there was an interaction of the host plant and fertilization with Calcium Aria or Sitam negatively affecting the fitness-related traits of the leaf miner. Application of these fertilizers resulted in delayed immature development of L. trifolii, decreased survival rate, and reduced adult longevity and fecundity. The activity of cinnamyl alcohol dehydrogenase (CAD), peroxidase (POD), polyphenol oxidase (PPO), and phenylalanine ammonia-lyase (PAL) enzymes, as well as phenolic, flavonoid, and lignin content were higher in Calcium Aria + Sitam fertilized plants, intermediate in Calcium Aria and Sitam treated plants, and the lower in unfertilized plants. The development and survival of L. trifolii on different host plants, considering fertilization options, become important for deploying cultural control practices against this important pest species.

Ultraviolet‐B Stress Increases Epidermal UV‐Screening Effectiveness and Alters Growth and Cell‐Wall Constituents of the Brown Midrib bmr6 and bmr12 Mutants of Sorghum bicolor

ABSTRACTThe brown midrib bmr6 and bmr12 mutants of sorghum (Sorghum bicolor) have alterations to the phenylpropanoid pathway impairing the activity of cinnamyl alcohol dehydrogenase (CAD) and/or caffeate5/hydroxyferulate O‐methyl transferase (COMT) enzymes, which inhibit lignin synthesis. Interestingly, these phenylpropanoids can also act as sunscreen compounds in plants and potentially attenuate ultraviolet radiation. We examined the effects of ultraviolet‐B (UV‐B; 280–320 nm) exclusion on growth, cell‐wall constituents and UV‐screening abilities of bmr6, bmr12, a double mutant (bmr6 bmr12; dm) and wild‐type (WT) genotypes of S. bicolor. Plants were grown in a UV‐transparent greenhouse under filters that either transmitted 2.8% (Mylar) or 90% (Aclar) of UV‐B. The greenhouse experiment was a 2 × 4 (UV treatment × genotype) complete factorial design. Sorghum grown under reduced UV were 23% taller and had 22% fewer leaves. Among genotypes, the WT plants were 5%–12% taller than the bmr6, bmr12 and dm mutants. The near‐ambient UV‐B treatment group was more effective at UV screening and had a 16% higher UV‐screening effectiveness than those under reduced UV‐B. Sorghum plants with the bmr6 and dm genotypes had 8%–19% higher UV‐shield than the bmr12 and WT. Plants grown under the reduced UV‐B treatment had 5% less hemicellulose and 6% more cellulose in their cell walls. There were no overall treatment effects on bulk soluble phenolics, chlorophyll fluorescence (Fv/Fm) or lignin concentrations. These results are a possible indication that the bmr mutants of S. bicolor have a varied response to UV‐B exclusion due to alterations in the phenylpropanoid pathway leading to redistribution of metabolites.

Genome-wide identification and expression patterns in response to signals from cadmium of StCADs gene family in potato (Solanum tuberosum L.)

BackgroundWith the rapid development of the economy and society, soil pollution is becoming more and more serious. Heavy metal cadmium (Cd) pollution is one of the typical problems, which poses a potentially serious threat to crop production and human health. Cinnamyl alcohol dehydrogenase (CAD) is a key enzyme in lignin synthesis and plays an important role in plant resistance to external stress. In this study, combined with bioinformatics analysis and expression pattern analysis, the members of the potato CAD family were identified, and their physical and chemical properties, evolutionary characteristics and chromosome location were clarified, as well as their regulatory effects on Cd tolerance.ResultsA total of 50 StCAD genes belonging to 6 subfamilies were obtained, and all of them were located in the cytoplasm. Members of the same family had similar gene structures and functional domains. The promoter region of each StCAD family member contains at least 5 or more abiotic stress response elements, indicating that the family had potential functions in regulating stress. According to the expression pattern analysis, most genes in this family were upregulated after Cd stress, further enhanced CAD activity and significantly promoted lignin accumulation in potato roots.ConclusionIn summary, the StCAD family plays an important role in potato response to Cd stress. This study lays a foundation for further studies on the functions of the StCAD family and provides candidate genes for Cd resistance molecular breeding in potato.Graphical

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.

Calcium chloride treatment maintains quality and enhances antioxidant capacity of fresh-cut carrots through modulating DcCMLs-DcCAMTA3-mediated phenylpropanoid pathway

Whitening and microbial infection are two major reasons to induce quality deterioration in fresh-cut carrots. Calcium chloride (CaCl2) could enhance the quality attributes in fresh-cut carrots, but the molecular mechanism is still not illuminated. In this study, CaCl2 treatment suppressed the increases of whiteness index and total bacterial count as well as enhanced the antioxidant capacity of fresh-cut carrots. In addition, CaCl2 treatment promoted phenolics accumulation by upregulating the transcripts and enzyme activity of phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H) and 4-coumarate coenzyme A ligase (4CL) in phenylpropanoid pathway. However, this treatment inhibited the increase of enzyme activity and gene expression of cinnamyl alcohol dehydrogenase (CAD), thus suppressing lignin synthesis and whitening process in fresh-cut carrots. Moreover, a calmodulin-binding transcription activator (CAMTA) transcription factor DcCAMTA3, was induced in response to CaCl2 treatment. DcCAMTA3 activated the transcription of DcPAL1, DcC4H and Dc4CL1 genes and repressed the expression of DcCAD1 gene by directly targeting the CG-box. DcCML3/11, a calmodulin-like protein, interacted with DcCAMTA3, and this interaction enhanced DcCAMTA3-mediated transcriptional activation of DcPAL1, DcC4H and Dc4CL1 and repression of DcCAD1. Therefore, CaCl2 treatment is effective in maintaining quality and enhancing antioxidant capacity of fresh-cut carrots by the cooperative action of DcCMLs and DcCAMTA3 in positively regulating phenylpropanoid pathway.

Ferulic acid enhanced resistance against blue mold of Malus domestica by regulating reactive oxygen species and phenylpropanoid metabolism

Postharvest decay of fruit caused by phytopathogen often causes tremendous losses during logistics. Ferulic acid is a kind of phenolic acid which has potential antimicrobial ability and initiates defense responses. This study performed to evaluate the induced resistance of ferulic acid against blue mold of apples (cv. Qiujin) as well as the mechanism involved in its action. Results suggested that 1.0 g L−1 ferulic acid remarkably reduced lesion diameter of Penicillium expansum-inoculated apples and colony diameter in vitro. The activities and gene expressions of catalase, superoxide dismutase, peroxidase, dehydroascorbate reductase, glutathione reductase, monodehydroascorbate reductase, ascorbate peroxidase, and nicotinamide adenine dinucleotide phosphate oxidase were distinctly improved by ferulic acid immersion. Ferulic acid also promoted ascorbic acid and reduced glutathione contents, whereas decreased hydrogen peroxide and malondialdehyde contents in apples. Moreover, ferulic acid enhanced the gene expressions and activities of cinnamyl alcohol dehydrogenase, 4-coumarate coenzyme A ligase, cinnamate-4-hydroxylase, and phenylalanine ammonia-lyase, resulting in caffeic acid, flavonoids, lignin, total phenolics, and p-coumaric acid accumulation in apples. Taken together, ferulic acid could activate the activities and gene expressions of the key enzymes in phenylpropanoid pathway as well as reactive oxygen species metabolism to promote the synthesis of antioxidants and secondary metabolites, thereby increasing disease resistance of apples.

Hydrogen sulfide delays yellowing and softening, inhibits nutrient loss in postharvest celery

Celery is an important leafy vegetable crop and is widely used in fresh food consumption and processing. Therefore, the preservation of fresh cut celery is warranted. As a food preservative, sodium hydrosulfide has been used to maintain postharvest quality of crops. However, the role of sodium hydrosulfide in the preservation of postharvest celery remains unclear. Here, by regulating endogenous hydrogen sulfide content with sodium hydrosulfide and hypotaurine, we evaluated the effects of sodium hydrosulfide on postharvest celery quality. Sodium hydrosulfide treatment promoted endogenous hydrogen sulfide accumulation by triggering AgLCD and AgSAT expression, as well as increased activity of L-cysteine desulfhydrase, D-cysteine desulfhydrase, O-acetylserine (thiol)lyase, and serine acetyltransferase. Simultaneously, sodium hydrosulfide treatment enhanced the expression of AgSOD1, AgPOD, and AgCAT, improved the activities of superoxide dismutase, peroxidase, and catalase, and inhibited the accumulation of malondialdehyde, hydrogen peroxide, and superoxide anion, thereby reducing electrolyte leakage of the cell membrane. AgPAL and AgCAD expressions were up-regulated, and phenylalanine ammonia-lyase and cinnamyl alcohol dehydrogenase activities were increased to promote lignin synthesis and alleviate the softening process. AgPAO and AgPPH expression was down-regulated, polyamine oxidases and pheophytinase activities were decreased to inhibit chlorophyll degradation and delay yellowing. Meanwhile, sodium hydrosulfide treatment effectively inhibited nutrient loss, including soluble sugar, soluble protein, vitamin C, carotenoids, and total phenols. Our findings suggest that hydrogen sulfide plays an essential role in delaying quality deterioration of postharvest celery, while sodium hydrosulfide treatment is a promising method for celery preservation.

Exogenous Glutathione enhances tolerance of the potato (Solanum tuberosum L.) to cadmium stress by regulating the biosynthesis of phenylpropanoid and the signal transduction of plant hormones

BackgroundCadmium (Cd) pollution has brought harm to the growth and development of potato. Glutathione (GSH) is an important antioxidant that may play an active role in the response of a potato to Cd stress. However, how GSH influences the effect of Cd on potatoes is unknown. In this study, we investigated the effects of exogenous GSH on the phenylpropanoid biosynthesis pathway and plant hormone signal transduction pathway in potatoes under Cd stress to explore new ideas for how potatoes respond to Cd stress. We cultured 21-day-old 'Atlantic’ plantlets in Murashige and Skoog (MS) medium supplemented with 500 μmol/L CdCl2 or 500 μmol/L CdCl2 + 400 μmol/L GSH. We then investigated the activities of key enzymes in the phenylpropanoid biosynthesis pathway, hormone levels, and the expression levels of related genes at different time points.ResultsAnalysis showed that 96 h of treatment with glutathione led to an increase in the expression levels of genes encoding phenylalanine ammonia-lyase (PAL), cinnamyl alcohol dehydrogenase (CAD) and peroxidase (POD); an increase in the enzymic activities of PAL, CAD and POD; and an increase in the content of lignin. The content of lignin was positively correlated with the expression levels of several genes (PAL: PG0031457, CAD: PG0005359, POD: PG0011640 and PG0015106). In addition, the levels of Salicylic acid (SA) and Jasmonic acid (JA) increased significantly, the expression levels of the genes encoding transcription factor TGA (PG2023696), pathogenesis-related protein 1 (PR1) (PG0005111), and the transcription inhibitor Aux/IAA (PG0006093) all increased while the expression levels of jasmonate ZIM domain-containing protein (JAZ) (PG0004367), auxin influx carrier (AUX) (PG0006550) and auxin response factor (ARF) (PG0005794) all decreased. We also observed a reduction in the content of IAA.ConclusionExogenous GSH improved the tolerance of potato, Atlantic cv. to Cd stress by regulating the phenylpropanoid biosynthesis pathway and the plant hormone signal transduction pathway.Graphical

Comparative Physiological Analysis of Lignification, Anthocyanin Metabolism and Correlated Gene Expression in Red Toona sinensis Buds during Cold Storage

The characteristics of anthocyanin and lignin are important parameters in evaluating the quality of red Toona sinensis buds. Red T. sinensis buds are prone to senescence during postharvest storage, which subsequently affects their quality and sales. However, the mechanism of senescence in red T. sinensis buds under low-temperature conditions remains unclear. In this study, red T. sinensis buds were stored at 4 °C, and their anthocyanin and lignin contents as well as the enzyme activities of PAL (phenylalanine ammonia lyase), 4CL (4-coumarate-CoA ligase), CAD (cinnamyl alcohol dehydrogenase) and POD (peroxidase) were determined at 0, 1, 2 and 3 d after handing. Meanwhile, the cellular structure of postharvest red T. sinensis buds was observed by microscopy. The relative expression of lignin-related and anthocyanin-related genes was analyzed using qRT-PCR. The results show that the anthocyanin content of the leaves was higher than that of the petioles. After 3 d of storage, the anthocyanin content of the leaves was 4.66 times that of the petioles. Moreover, the lignin content of the red T. sinensis buds gradually increased. Compared with 0 d, the lignin content of the leaves and petioles increased by 331.8 and 94.14 mg·g−1, respectively. The enzyme activities of PAL, 4CL, CAD and POD increased during cold storage. The intercellular space and the arrangement of the palisade tissue and sponge tissue in the mesophyll of red T. sinensis buds became smaller and closer, respectively. The secondary cell wall of xylem cells thickened, the number of xylem cells increased, and the arrangement number of the xylem cells became closed in the leaf vein and petioles during red T. sinensis bud storage. The expression levels of anthocyanin-related (Except for TsCHS and TsANS) and lignin-related genes increased during red T. sinensis bud storage and are highly consistent with the accumulation patterns of anthocyanins and lignin. This study may serve as a reference for exploring the molecular mechanisms of senescence, regulating the quality and cultivating new varieties of red T. sinensis buds that have low lignin content but high anthocyanin content after harvest.

Essential oils nano-emulsion confers resistance against Penicillium digitatum in 'Newhall' navel orange by promoting phenylpropanoid metabolism

Inducing natural resistance against pathogen infection in postharvest citrus by exogenous elicitor is a promising alternative to reduce postharvest losses. Here, the potential induced resistance mechanism of blended cinnamaldehyde, carvacrol and eugenol nano-emulsion against P. digitatum in ‘Newhall’ navel orange (Citrus sinensis (L.) Osbeck) was evaluated through combined transcriptomic and metabolomics analysis. Application of nano-emulsion maintained fruit firmness after P. digitatum inoculation, nano-emulsion reduced H2O2 and MDA accumulation of citrus fruit, increased PAL, C4H, 4CL and CAD activity, and higher contents of flavonoids, lignin and total phenolic compounds. Furthermore, higher activities of SOD, CAT, POD and APX in nano-emulsion treated fruit possibly benefited reducing ROS accumulation and lipid peroxidation. The activities of the defense enzymes CHI, GLU were higher in the nano-emulsion treated fruits. RNA-seq identified 653 differentially expressed genes (DEGs) between the control and the nano-emulsion-treated fruit at 48 hpi, including 444 up-regulated and 209 downregulated genes. Genes encoding shikimate O-hydroxycinnamoyltransferase (HCT), caffeoyl-CoA O-methyltransferase (CCoAOMT), caffeic acid 3-O-methyltransferase / acetylserotonin O-methyltransferase (COMT), cinnamyl-alcohol dehydrogenase (CAD) and peroxidase (POD) were differentially expressed by nano-emulsion treatment. In addition, 175 differential accumulated metabolites between the control and the nano-emulsion-treated fruit at 48 hpi also were identified, the different accumulated metabolites from phenylpropanoid biosynthesis pathway related with disease resistance including L-phenylalanine, caffeic acid, caffeoyl quinic acid, coniferyl alcohol, coniferaldehyde. The integrated transcriptomic and metabolomic profiling indicated that the differentially expressed genes (DEGs) and the differentially accumulated metabolites (DAMs) were mainly involved in phenylpropanoid biosynthesis pathway. Besides, the nano-emulsion significantly induced accumulation of primary metabolites including amino acids, soluble sugars, organic acids, lipids, sugar and alcohols. All these results indicated that blended essential oil nano-emulsion as an antifungal delivery system to induce resistance against P. digitatum infection of ‘Newhall’ navel orange by promoting phenylpropanoid metabolism.

Preharvest L-phenylalanine sprays accelerated wound healing of harvested muskmelons by eliciting phenylpropanoid metabolism and enzymatic browning

L-phenylalanine (L-phe) is the initial substrate of phenylpropanoid metabolism. This study aimed to investigate the effect of four preharvest spray with 8 mM L-phe during fruit development and wound healing ability in harvested muskmelons (cv. Manao) and to explore the related mechanisms. The results revealed that preharvest L-phe sprays promoted phenylalanine ammonialyase, cinnamate-4-hydroxylase, 4-coumaric acid coenzyme A ligase and cinnamyl alcohol dehydrogenase activities, and elevated the level of four phenolic acids (p-coumaric, caffeic, cinnamic, ferulic acids), three lignin monomers (sinapyl, coniferyl, cinnamyl alcohols), total phenols, flavonoids and lignin at wounds of harvested fruit. L-phe treatment increased peroxidase activity, H2O2 level, and accelerated the deposition of suberin polyphenolic and lignin at wounds, which led to lower weight loss and disease index of harvested muskmelons during healing. Moreover, the treatment enhanced polyphenol oxidase activity and induced enzymatic browning at wounds. Thus, preharvest L-phe sprays promoted wound healing of harvested muskmelons by eliciting phenylpropannoid metabolism and enzymatic browning at wounds.

Transcriptional and metabolic changes associated with internode development and reduced cinnamyl alcohol dehydrogenase activity in sorghum.

The molecular mechanisms associated with secondary cell wall (SCW) deposition in sorghum remain largely uncharacterized. Here, we employed untargeted metabolomics and large-scale transcriptomics to correlate changes in SCW deposition with variation in global gene expression profiles and metabolite abundance along an elongating internode of sorghum, with a major focus on lignin and phenolic metabolism. To gain deeper insight into the metabolic and transcriptional changes associated with pathway perturbations, a bmr6 mutant [with reduced cinnamyl alcohol dehydrogenase (CAD) activity] was analyzed. In the wild type, internode development was accompanied by an increase in the content of oligolignols, p-hydroxybenzaldehyde, hydroxycinnamate esters, and flavonoid glucosides, including tricin derivatives. We further identified modules of genes whose expression pattern correlated with SCW deposition and the accumulation of these target metabolites. Reduced CAD activity resulted in the accumulation of hexosylated forms of hydroxycinnamates (and their derivatives), hydroxycinnamaldehydes, and benzenoids. The expression of genes belonging to one specific module in our co-expression analysis correlated with the differential accumulation of these compounds and contributed to explaining this metabolic phenotype. Metabolomics and transcriptomics data further suggested that CAD perturbation activates distinct detoxification routes in sorghum internodes. Our systems biology approach provides a landscape of the metabolic and transcriptional changes associated with internode development and with reduced CAD activity in sorghum.

H-lignin can be deposited independently of CINNAMYL ALCOHOL DEHYDROGENASE C and D in Arabidopsis.

Lignin contributes substantially to the recalcitrance of biomass toward saccharification. To circumvent this problem, researchers have genetically altered lignin, although, in a number of cases, these efforts have resulted in an undesirable yield penalty. Recent findings have shown that by knocking out two subunits (MED5A and MED5B) of the transcriptional regulatory complex Mediator, the stunted growth phenotype of mutants in p-coumaroyl shikimate 3'-hydroxylase, reduced epidermal fluorescence 8-1 (ref8-1), can be alleviated. Furthermore, these plants synthesize a lignin polymer almost entirely derived from p-coumaryl alcohol. Plants deficient in cinnamyl alcohol dehydrogenase (CAD) are notable in that they primarily incorporate coniferaldehyde and sinapaldehyde into their lignin. We tested the hypothesis that by stacking mutations in the genes encoding for the CAD paralogs C and D on an Arabidopsis (Arabidopsis thaliana) med5a/5b ref8-1 genetic background, the biosynthesis of p-coumaryl alcohol would be blocked, making p-coumaraldehyde available for polymerization into a novel kind of lignin. The med5a/5b ref8-1 cadc cadd plants are viable, but lignin analysis demonstrated that they continue to synthesize p-hydroxyphenyl lignin despite being mutated for the CADs typically considered to be required for monolignol biosynthesis. In addition, enzyme activity tests showed that even in the absence of CADC and CADD, there is high CAD activity in stems. We tested the potential involvement of other CADs in p-coumaraldehyde biosynthesis in the quintuple mutant by mutating them using the CRISPR/Cas9 system. Lignin analysis demonstrated that the resulting hextuple mutant plants continue to deposit p-coumaryl alcohol-derived lignin, demonstrating a route for the synthesis of p-hydroxyphenyl lignin in Arabidopsis independent of four CAD isoforms.

Impact of melatonin application on lignification in water bamboo shoot during storage.

Melatonin, a crucial bioactive molecule, involved in several physiological processes in plants. This study investigated the effects of melatonin (MT) treatment on lignification, including firmness, lignin, lignified-enzyme activities, the expression patterns of genes encoding corresponding enzymes and transcription factors in water bamboo shoot during storage for 8days. MT treatment decreased the firmness and content of lignin. It inhibited the degradation of total phenols and ascorbic acid and delayed the lignin biosynthesis, via reducing the activities of phenylalanine ammonia-lyse cinnamyl alcohol dehydrogenase and peroxidase, as well as lignin biosynthesis-related genes expression levels. Transcription factors of ZlNAC1, ZlNAC2, ZlNAC3 and ZlNAC4 from NAC family and ZlMYB1 and ZlMYB2 from MYB family were increased in water bamboo shoot after harvest and MT-treated markedly reduced their expression. Therefore, our findings supply a fundamental understanding of MT treatment suppression of lignification and establish a foundation for further research on transcriptional regulation.

Sorbitol immersion accelerates the deposition of suberin polyphenolic and lignin at wounds of potato tubers by activating phenylpropanoid metabolism

Sorbitol is the primary product of photosynthesis and sugar metabolism in plants. However, the mechanism by which sorbitol treatment affects potato tuber wound healing remains unclear. This study showed that sorbitol treatment reduced weight loss and disease index (inoculated with Fusarium sulphureum) of tubers during healing. Sorbitol also facilitated the accumulation of suberin polyphenolic (SPP) and lignin at the wounded sites. Sorbitol treatment activated the activities of phenylalanine ammonia-lyase (PAL), 4-coumaryl-CoA ligase (4CL), cinnamic acid-4-hydroxylase (C4H), and cinnamyl alcohol dehydrogenase (CAD), and increased the levels of individual phenolic acids and lignin monomers. In addition, sorbitol treatment increased the H2O2 level and peroxidase (POD) activity. It was suggested that sorbitol treatment could activate phenylpropanoid metabolism, and promote SPP and lignin deposition at the wound sites of potato tubers.

Diphenyleneiodonium delays the deposition of suberin polyphenolic and lignin at wounds of potato tubers by inhibiting Strbohs transcription and NADPH oxidase activity

Diphenyleneiodonium (DPI) is a specific and effective inhibitor of NADPH oxidase (NOX). However, there are no reports on whether DPI affects the transcription of Strbohs family members, and the accumulation of suberin polyphenolic (SPP) and lignin of potato tubers during healing. In this study, DPI treatment was shown to exert an inhibitory effect on the expression of Strbohs at the wound tissue, especially StrbohA, StrbohB, and StrbohE. DPI clearly reduced the activity of NOX and superoxide dismutase, and decreased O2− and H2O2 accumulation. DPI also decreased the activity of phenylalanine ammonia-lyase, cinnamate-4-hydroxylase, 4-coumarate-CoA ligase, and cinnamyl alcohol dehydrogenase as well as the contents of total phenolics and lignin. Moreover, DPI caused the lower deposition amount of SPP and lignin at wounds of potato tubers. Above results suggested that DPI led to the less SPP and lignin deposition at the wound surfaces by decreasing H2O2 production via Strbohs / NOX and suppressing phenylpropanoid metabolism in potato tubers.

Cinnamic acid treatment reduces the surface browning of fresh-cut taro

The efficacy of cinnamic acid (CA) as an antibrowning agent was evaluated in fresh-cut taro. Different concentrations (0.1 g L−1, 0.2 g L−1 and 0.4 g L−1) of CA treatments reduced the browning index and a* and b* values but maintained L* values, suggesting that CA treatments prevented the browning development of fresh-cut taro during storage. Among the concentrations used, 0.1 g L−1 CA was sufficient to reduce browning. CA treatment (0.1 g L−1) reduced the total flavonoid content and the activity and gene expression of four main enzymes (PAL, C4H, 4CL and CHS) in the flavonoid biosynthesis pathway, suggesting that CA treatment reduced taro browning by suppressing the de novo biosynthesis of flavonoid compounds. Furthermore, CA treatment significantly reduced the lignin content, activity and gene expression of cinnamyl-alcohol dehydrogenase and slightly reduced the firmness of taro slices. Moreover, CA treatment showed strong inhibition of PPO activity in vivo and in vitro, suggesting that CA reduced phenolic oxidation by inhibiting PPO activity. CA-treated taro showed significantly reduced hydrogen peroxide content but enhanced activity and gene expression of catalase and peroxidase. In addition, CA had strong radical scavenging activity, suggesting that the application of CA to fresh-cut taro enhanced antioxidant activity. Overall, CA treatment reduced the surface browning of fresh-cut taro by suppressing the activity of browning-related enzymes and by improving antioxidant activity. The results presented in this study indicate that CA is an effective natural antibrowning agent for fresh-cut taro.

Pichia galeiformis Induces Resistance in Postharvest Citrus by Activating the Phenylpropanoid Biosynthesis Pathway.

This study aimed to investigate the effect of Pichia galeiformis on disease resistance and elucidate the changes in phenylpropane biosynthesis treated by P. galeiformis in postharvest citrus. The results showed that P. galeiformis reduced the disease incidence and lesion diameters without direct contact with the pathogen Penicillium digitatum. Transcriptome analysis revealed that phenylpropanoid biosynthesis was triggered by P. galeiformis. Genes encoding phenylpropanoid biosynthesis were upregulated, including phenylalanine ammonia-lyase (PAL), 4-coumaroyl-CoA ligase (4CL), cinnamate-4-hydroxylase (C4H), peroxidase (POD), cinnamyl alcohol dehydrogenase (CAD), O-methyltransferase, and hydroxyl cinnamoyl transferase. Moreover, P. galeiformis increased the activity of PAL, 4CL, C4H, POD, polyphenol oxidase, and CAD in citrus pericarp. In addition, P. galeiformis treated citrus displayed higher levels of total phenolic compounds, flavonoid, and lignin and higher amounts of ferulic and sinapic acid. In conclusion, these results suggested that P. galeiformis could induce resistance through modulating the pathway of phenylpropanoid biosynthesis in postharvest citrus.

Dose effect of exogenous abscisic acid on controlling lignification of postharvest kiwifruit (Actinidia chinensis cv. hongyang)

Postharvest ‘Hongyang’ fruit is susceptible to low temperature in storage, which results in black patches on the peel and lignification in the pulp. Abscisic acid (ABA) has been shown to enhance the cold tolerance of many other postharvest fruits. This study investigated whether applying ABA can control chilling injury (CI) of ‘Hongyang’ during storage at 0 °C. Fruit were pretreated with 0–50 mg/L ABA, and then the CI symptoms and lignin accumulation processes were analyzed and microscope observations were performed during low temperature storage. The results showed that there is dose effect on controlling lignification. For example, 50 mg/L ABA treatment increased phenylalanine ammonialyase (PAL), cinnamyl alcohol dehydrogenase (CAD) and peroxidase (POD) activity, which are crucial for lignin synthesis, and sharply upregulated expression of the AcPAL, AcCAD and AcPOD genes. However, 20 mg/L ABA alleviated black patch symptoms, increased lignin content in the peel, and did not negatively affect fruit quality. The higher total antioxidant capacity (ORAC) of edible part was maintained by 20 mg/L ABA treatment. Furthermore, microscope observations showed that 20 mg/L ABA decreased the number of lignin cells with a diameter of 40–80 μm, thus reducing the chance of lignification in the pulp.

Cloning, expression analysis and molecular marker development of cinnamyl alcohol dehydrogenase gene in common wheat.

In common wheat, stem strength is one of the key factors for lodging resistance, which is influenced by lignin content. Cinnamyl alcohol dehydrogenase (CAD) is a vital enzyme in the pathway of lignin biosynthesis. Cloning and marker development of the CAD gene could be helpful for lodging resistance breeding. In this study, the full-length genomic DNA sequence of CAD gene in wheat was cloned by using homologous strategy. A marker 5-f2r2 was developed based on CAD sequence and used to genotype 258 wheat lines. Four haplotype combinations of CAD genes were identified in 258 wheat lines. Correction analyses among the CAD gene expression, CAD activity, and stem strength indicated significant positive correlation between CAD gene expression and CAD activity, between wheat CAD activity and wheat stem strength. The haplotype combination B is significantly associated with the lower enzyme activity and weak stem strength, which was supported by the level of CAD gene expression. The CAD activity and stem strength of wheat could be distinguished to some extent using this pair of specific primer 5-f2r2 designed in this study, indicating that the sequence targeted site (STS) marker 5-f2r2 could be used in marker assistant selection (MAS) breeding.