Cinnamyl Alcohol Dehydrogenase Activity Research Articles

Reactive oxygen species-mediated the accumulation of suberin polyphenolics and lignin at wound sites on muskmelons elicited by benzo (1, 2, 3)-thiadiazole-7-carbothioic acid S-methyl ester

• BTH rapidly stimulated ROS production at wound sites on muskmelons. • ROS elicited by BTH activated phenylpropanoid metabolism at wound sites. • BTH promoted SPP and lignin accumulation at wound sites. • DPI inhibited wound healing process promoted by BTH at wound sites. Benzo (1, 2, 3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH) is the first synthetic nontoxic chemical elicitor that has induced resistance in fruit and vegetables against postharvest diseases. In this study, we treated artificially wounded muskmelon fruit ( Cucumis melo L. cv. Perfect) with 100 mg L -1 BTH. The results indicated that there was a significant accumulation of suberin polyphenolics and lignin at wound sites on the treated fruit as well as a noticeable decrease in weight loss of wounded fruit during healing. The BTH treatment also enhanced the activity of NADPH oxidase and superoxide dismutase, increasing the production of O 2 •- and H 2 O 2 . Moreover, BTH activated the activity of phenylalanine ammonia-lyase, cinnamate-4-hydroxylase, 4-coumarate-CoA ligase, and cinnamyl alcohol dehydrogenase as well as elevating the levels of cinnamic acid, p -coumaric acid, caffeic acid, ferulic acid, sinapic acid, coniferyl alcohol, sinapyl alcohol, and lignin at the wound sites on the treated fruit. When we treated the BTH-treated muskmelons with 50 μmol L -1 diphenylene iodonium (DPI), the treatment partially inhibited the accumulation of polyphenolic substances and lignin at wound sites on the treated fruit, weakened the activity of NADPH oxidase and superoxide dismutase, and reduced the production of O 2 .- and H 2 O 2 . Furthermore, BTH combined with DPI treatment caused lower activity of key enzymes and lower level of metabolites in phenylpropanoid pathway compared with BTH treatment. Considering DPI as a reactive oxygen species inhibitor, we suggest that reactive oxygen species could be a second messenger for activating phenylpropanoid metabolism, as a consequence for promoting polyphenolic substances and lignin accumulation and reducing weight loss in the BTH-treated muskmelons during healing.

Discovering Biomass Structural Determinants Defining the Properties of Plant-Derived Renewable Carbon Fiber

SummaryTraditional lignocellulosic feedstock research has focused on biomass characteristics essential for improving saccharification efficiency, yet the key biomass features underlying high-quality renewable lignin materials remain unknown. Nevertheless, modern biorefinery cannot achieve sustainability and cost-effectiveness unless the lignin stream can be valorized. We hereby addressed these scientific gaps by investigating biomass characteristics defining lignin-based carbon materials properties. Lignin from eight sorghum samples with diverse characteristics was fabricated into carbon fibers (CFs). Remarkably, only lignin uniformity was found to define CF mechanical performance, highlighting the new structure-property relationship. Contrarily, lignin content and composition did not impact on carbon material properties. Mechanistic study by XRD and Raman spectroscopy revealed that higher lignin uniformity enhanced CF microstructures, in particular, turbostratic carbon content. The study for the first time highlighted lignin uniformity as an important biomass structure determinant for renewable products, which opened up new avenues for feedstock design toward diverse products enabling sustainable and cost-effective bioeconomy.

Lignin synthesized by CmCAD2 and CmCAD3 in oriental melon (Cucumis melo L.) seedlings contributes to drought tolerance.

CmCAD2 and CmCAD3 function more positively than CmCAD1 in oriental melon for lignin synthesis which is important to ensure internal water status and thus for drought tolerance. Well-lignification may be the guarantee of efficient axial water transport and barrier of lateral water flow in oriental melon tolerating drought stress, however remains to be verified. As an important enzyme in monolignol synthesis pathway, five cinnamyl alcohol dehydrogenase (CAD) genes were generally induced in melon seedlings by drought. Here we further revealed the roles of CmCAD1, 2, and 3 in lignin synthesis and for drought tolerance. Results found that overexpressing CmCAD2 or 3 strongly recovered CAD activities, lignin synthesis and composition in Arabidopsis cadc cadd, whose lignin synthesis is disrupted, while CmCAD1 functioned modestly. In melon seedlings, silenced CmCAD2 and 3 individually or collectively decreased CAD activities and lignin depositions drastically, resulting in dwarfed phenotypes. Reduced lignin, mainly composed by guaiacyl units catalyzed by CmCAD3, is mainly due to the limited lignification in tracheary elements and development of Casparion strip. While CmCAD1 and 2 exhibited catalysis to p-coumaraldehyde and sinapaldehyde, respectively. Compared with CmCAD1, drought treatments revealed higher sensitivity of CmCAD2 and/or 3 silenced melon seedlings, accompanying with lower relative water contents, water potentials and relatively higher total soluble sugar contents. Slightly up-regulated expressions of aquaporin genes together with limited lignification might imply higher lateral water loss in stems of silenced lines. In Arabidopsis, CmCAD2 and 3 transgenic lines enhanced cadc cadd drought tolerance through recovering lignin synthesis and root development, accompanying with decreased electrolyte leakage ratios and increased RWCs, thus improved survival rates. Briefly, lignin synthesized by CmCAD2 and 3 functions importantly for drought tolerance in melon.

Effect of hot water treatment on chilling injury and lignification of cold-stored fresh areca nut (Areca catechu L.).

Fresh areca nut is widely favored by consumers in South and Southeast Asia. However, postharvest areca nut perished quickly and was vulnerable to chilling injury (CI) and lignification during traditional cold storage. In order to alleviate this situation, hot water treatment was applied to investigate its effect on CI and lignification of fresh areca nut during cold storage at 13°C. Areca nuts were submersed in hot water at 45°C (HW45) and 50°C (HW50) for short-term 5min compared to fruit submersed in water at 20°C (CT), then stored at 13°C with 90% humidity for 60days. CI, malondialdehyde (MDA), electrolyte leakage (EL), lignin and total phenolic content, related enzymes including phenylalanine ammonia-lyase (PAL), cinnamyl alcohol dehydrogenase (CAD) and peroxidase activity (POD) were examined. Results indicated that two HW treatments both induced chilling tolerance and delayed lignification of areca nut to varying degrees during cold storage compared with the CT. Among which, HW45 treated-areca nuts had the lowest CI, MDA content and EL while maintaining the highest total phenolic content. Moreover, no significant effects were found between HW45 and HW50 on tissue lignification, but they both effectively blocked lignin accumulation by inhibiting PAL, CAD and POD activities compared with the CT. The present study provided a safe physical method to mitigate CI and delay tissue lignification in cold-stored areca nut.

Slight Shading Stress at Seedling Stage Does not Reduce Lignin Biosynthesis or Affect Lodging Resistance of Soybean Stems

Shade is widespread in agricultural production and affects lignin biosynthesis and lodging resistance of crops. We explored the effects of shade intensity on lignin biosynthesis and lodging resistance at the physiological and molecular levels in two soybean cultivars (Nandou12 and E93) with different shade tolerance under four progressively severe shade treatments, S0–S3 (S0: no shade, S1: slight shade, S2: moderate shade, S3: heavy shade). Our results showed no significant difference in breaking strength of the two cultivars under S1 and S0 treatments, with no prominent decrease in the lodging resistance index. The activity of lignin biosynthesis rate-limiting enzymes phenylalanine ammonia-lyase (PAL), peroxidase and cinnamyl alcohol dehydrogenase (CAD), which were considerably related to the two lodging resistance indexes above, was not significantly decreased by slight shade, while 4-coumaric acid ligase (4CL) activity was increased. Most genes involved in lignin biosynthesis were not significantly down-regulated by slight shade (S1) compared to S0, while p-coumarate 3-hydroxylase (C3H), 4-coumaric acid ligase (4CL) and laccase (LAC) genes were upregulated. Under heavy shade (S3), enzyme activity and gene expression associated with lignin synthesis in both soybean cultivars were strongly inhibited; moreover, stem mechanical strength and lodging resistance were remarkably decreased compared with those under S0. These physiological and molecular changes suggested that applicable shade levels do not significantly affect the mechanical strength and lodging resistance of soybean stem. Exploiting the lodging resistance potential of existing soybean cultivars was an effective and efficient way to address yield reduction caused by lodging in intercropped soybeans.

Quality attributes of fresh common bean during storage as postharvest treatment with 1-MCP

ABSTRACT Fresh common beans were treated with 1-MCP at 0.5, 1.0, and 1.5 μL L−1 for 20 h at 25°C in an airtight chamber along with a control sample to evaluate the effect of 1-MCP concentration on the quality of fresh common bean during storage. The result showed that postharvest treatment with 0.5 μL L−11-MCP significantly suppressed the increase of peroxidase (POD), cinnamyl-alcohol dehydrogenase (CAD), phenylalnine ammonialyase (PAL), and cellulase (CEL) activity in fresh common bean, inhibited the transport of reducing sugar and increase in cellulose, delayed the increase in the length of pod tendon and electrolyte leakage, and retarded the decrease in the relative thickness of pods and firmness, and maintained the quality of fresh common beans. Our finding that postharvest 0.5 μL L−11-MCP could be used to maintain the quality of the fresh common bean.

Genotypic difference in secondary metabolism-related enzyme activities and their relative gene expression patterns, osmolyte and plant hormones in wheat.

Salinity and drought are the two most important and frequently co-occurring abiotic factors. A greenhouse pot experiment was carried out on two contrasting wheat genotypes (Jimai22, salt tolerant; Yangmai20, salt sensitive) to analyze the effect of drought (4% soil moisture content, D) and salinity (100 mM NaCl, S) either individually or combined on secondary metabolism-related enzyme activities and osmolytes. Results showed that drought, salinity and their combination (D + S) caused increases in phenylalanine ammonialyase (PAL, EC 4.3.1.24) activities compared with controls with a greater enhancement in Jimai22 than Yangmai20. Polyphenol peroxidase (PPO, EC 1.14.18.1) and shikimate dehydrogenase (SKDH, EC 1.1.1.25) activities increased more in Jimai22 both under salinity alone and D + S stresses. The D + S combination increased cinnamyl alcohol dehydrogenase (CAD, EC 1.1.1.195) activity and glycine betaine (GB) under both 10 and 4% soil moisture contents (SMC), and elevated abscisic acid (ABA), indole-3-acetic acid (IAA) and flavonoid contents at 4% SMC in Jimai22, contents of the compounds remained unchanged in Yangmai20. The treatment with salinity alone at both SMCs significantly increased callose and flavonoid contents in Jimai22 more than in Yangmai20, as compared to controls. In addition, the total phenol content at 4% SMC increased in the salt-tolerant genotype more. Moreover, total tocopherol under salinity alone and D + S at 4% SMC and chitinase activity under salinity at both SMC remarkably increased in Jimai22 while non-significant change observed in Yangmai20. Also, the expression of genes related to secondary metabolism (PAL, PPO, CAD, SKDH, and GB) was more induced in Jimai22 than Yangmai20 under D + S, and lower accumulation of H2 O2 and O2 - also occurred. Our findings suggest that high tolerance to D + S stress in Jimai22 was closely related to enhanced secondary metabolism-related enzyme activities and osmolytes such as PAL, CAD, PPO, SKDH, GB, total tocopherol, callose, plant hormones and their transcript level, which may beneficial to lower the reactive oxygen species (ROS) accumulation.

Microstructural and lignin characteristics in herbaceous peony cultivars with different stem strengths

Straight stems are highly important to herbaceous peony (Paeonia lactiflora Pall.) cut flowers. To clarify whether the microstructural and lignin characteristics are associated with P. lactiflora stem mechanical strength, eight cultivars were used to study their anatomical structure, secondary cell wall, lignin deposition, lignin content and structure, lignin biosynthetic enzyme activity and related gene expression levels. The results showed that stem diameter was a direct indicator estimating its mechanical strength. Simultaneously, the number of vascular bundles, area of vascular bundles, number of duct perforations, ratio of xylem to cross-section and thickness of secondary cell wall had significant positive correlations with stem mechanical strength. Moreover, three lignin monomers were all detected in the stem, and the contents of S-lignin, G-lignin and total lignin in high stem mechanical strength cultivars were higher than those in low stem mechanical strength cultivars as a whole, and lignin was deposited in the cell walls of the sclerenchyma, vascular bundle sheath and duct. Additionally, cinnamate 4-hydroxylase (C4H), cinnamyl alcohol dehydrogenase (CAD) and polyphenol oxidase (PPO) activities in high stem mechanical strength cultivars were higher than those in low stem mechanical strength cultivars as a whole, and CAD might be the key gene among detected lignin biosynthetic genes. Consequently, microstructural and lignin characteristics were closely correlated with stem mechanical strength in P. lactiflora. These results would provide useful information concerning the physiological mechanism of stem strength.

Inhibition effect of super atmospheric O2 packaging on H2O2-production and the key enzymes of ligin biosynthesis in fresh-cut Chinese cabbage

Fresh-cut Chinese cabbage was packaged by super atmospheric O2, and held at 4 °C, taking air packaging as control. The contents of lignin and H2O2 and, the activities and transcription expressions of four key enzymes of lignin synthesis, i.e., phenylalanine ammonia-lyase (PAL), 4-coumarate: CoA ligase (4-CL), cinnamyl alcohol dehydrogenase (CAD) and peroxidase (POD), were determined in the cabbage. The results showed that the lignin content of the cabbage packaged by super atmospheric O2 was markedly reduced (p < 0.05) in comparison with control from day 3 to 12 during storage at 4 ºC. The H2O2 concentrations in fresh-cut Chinese cabbage under super atmospheric O2 was lower than that of control during storage at 4 °C and, significantly lower (p < 0.05) on day 8 of storage. The activities of PAL, 4-CL, CAD and POD under super atmospheric O2 packaging were significantly lower (p < 0.05) than that of control from day 3 to 12 of storage at 4 ºC, except for 4-CL on day 9. Moreover, the transcript expressions of POD genes in the cabbage in super atmospheric O2 were dramatically reduced compared with control on day 8 of storage at 4 °C. It is suggested that the suppression of lignin synthesis of the cabbage under super atmospheric O2 packaging was attributed to the inhibition of H2O2, which feedback-regulated the key enzymes activities directly or indirectly.

Effects of Nanoparticles on Activity of Lignan Biosynthesis Enzymes in Cell Suspension Culture of Linum usitatissimum L.

Flax (Linum usitatissimum L.), as an important commercial crops, is a rich source of fatty acids, protein, dietary fiber and lignans. Flax plant has an effective anticancer activity due to lignan contents. Nanoparticles have recently been used as efficient non-biologic elicitors to improve the biosynthesis of secondary metabolites. In this study, the effects of different concentration of ZnO (0, 30, 60, and 120 mg/L) and TiO2 (0, 50, 100, and 150 mg/L) nanoparticles at different time (0, 24, 48, and 72 h) were investigated on enzyme activities and production of secondary metabolites in cell suspension cultures of flax. The results indicated that the highest activity of phenylalanine ammonia lyase (PAL) was observed in 30 mg/L nano-ZnO treatment at 48 h, whereas the effect of nano-TiO2 on PAL enzyme activity was not statistically significant. According to the results, the highest activity of CAD (cinnamyl alcohol dehydrogenase) was observed in 60 mg/L concentration of nano-ZnO at different intervals. The use of 150 mg/L nano-TiO2 led to increased activity of CAD. The maximum content of total phenol was detected at 150 mg/L nano-TiO2. Different concentrations of nano-TiO2, caused to an increase in total lignan at all intervals. The highest amount of total phenol and lignans was observed in 30 and 60 mg/L ZnO. In the present study, we were observed different effects of nanoparticle on enzymes activity and secondary metabolite production in cell suspension cultures of flax plant, depending on concentration and type of nanoparticles.

Differential expression of genes encoding phenylpropanoid enzymes in an apricot cultivar (Prunus armeniaca L.) with cleavable endocarp

Phenylpropanoid pathway related genes were identified and analyzed by co-expression network and expression pattern. NST1 may regulate the expression of CAD to affect the lignin deposition of ‘Liehe’ apricot endocarp. Apricot (Prunus Armeniaca L.) is a typical Rosaceae stone fruit tree. The extensive lignification of its endocarp is an important metabolic event during fruit ripening. There are abundant apricot germplasm resources in China, including a special apricot cultivar, ‘Liehe’ (LE), which has a thin, soft, cleavable endocarp with a hardness 45.84% that of the ‘Jinxihong’ (JG) apricot (with normal hardened-endocarp). To understand the molecular mechanisms behind the LE phenotype, differentially expressed genes (DEGs) encoding key enzymes involved in phenylpropanoid biosynthesis were mined from transcriptome data by the co-expression network and expression patterns. DEGs encoding key enzymes involved in phenylpropanoid biosynthesis were significantly down-regulated in LE, and the activity of these enzymes exhibited similar results. NST1 (NAC secondary wall thickening promoting factor 1) expression levels in LE were only 13.7%, 2.8%, 9.4%, and 82.5% that in JG at 9, 15, 21, and 30 days after full bloom (DAFB), respectively. CAD (Cinnamyl alcohol dehydrogenase) expression levels in LE were 1.3%, 0.7%, 0.2% and 2.7% that in JG at 15, 21, 30, 49 DAFB, respectively. CAD activity in LE was 46.4% and 63.6% that in JG at 42 and 49 DAFB, respectively. We thus used homologous cloning to determine the sequence differences of CAD and NST1 in LE and JG. Our results will help understand the molecular mechanisms underlying endocarp cleavage in LE apricot and provide a useful reference for further investigation of lignification during endocarp development. NST1 may regulate CAD which involved in the phenylpropanoid pathway and affect lignin deposition in LE endocarp.

EjHAT1 Participates in Heat Alleviation of Loquat Fruit Lignification by Suppressing the Promoter Activity of Key Lignin Monomer Synthesis Gene EjCAD5.

Texture attributes such as firmness and lignification are important for fruit quality. Lignification has been widely studied in model plants and energy crops, but fruit lignification has rarely been investigated, despite having an adverse effect on fruit quality and consumer preference. Chilling-induced loquat fruit lignification that occurs after harvest can be alleviated by heat treatment (HT) applied prior to low temperature storage. Enzyme activity assay showed that HT treatment could retard the low temperature-induced increase in cinnamyl alcohol dehydrogenase (CAD) activity. Transcript analysis and substrate activity assays of recombinant CAD proteins highlighted the key role of EjCAD5 in chilling-induced lignin biosynthesis. A novel homeobox-leucine zipper protein ( EjHAT1) was identified as a negative regulator of EjCAD5. Therefore, the effect of HT treatment on lignification may be partially due to the suppression of the EjCAD5 promoter activity by EjHAT1.

Benzo-(1, 2, 3)-thiadiazole-7-carbothioic acid s-methyl ester (BTH) promotes tuber wound healing of potato by elevation of phenylpropanoid metabolism

Suberization induced by wounding is essential to the healing process decreasing pathogen infection and water loss. The effect of postharvest treatment with benzo-(1, 2, 3)-thiadiazole-7-carbothioic acid s-methyl ester (BTH) on tuber wound healing was investigated on potato (cv. Longshu No. 3). BTH treatment reduced weight loss and disease index caused by Fusarium sulphureum of the tubers, and enhanced the firmness of healing tissues. The elevated autofluorescence intensity of suberin and stained lignin thickness indicated effects of BTH dipping during healing. The contents of major substrates of suberin synthesis, cinnamic, caffeic and ferulic acids increased in BTH-treated tubers along with the phenols and lignin contents. These biochemical changes during wound healing were correlated with the increased activities of phenylalanine ammonia-lyase, cinnamate-4-hydroxylase, 4-coumaryl-CoA ligase and cinnamyl alcohol dehydrogenase. The presented results suggested that BTH treatment stimulated wound-induced suberization in harvested potato tubers and reduced fungal dry rot by elevating the metabolism of phenylpropanoid pathway.

Amelioration of cadmium stress in Withania somnifera by ROS management: active participation of primary and secondary metabolism

Cadmium (Cd) is considered as a non-essential heavy metal with substantial toxicity on environment. Withania somnifera, a reputed therapeutic herb exhibits vast pharmacological activities due to the presence of steroidal lactones-withanolides. The present study deals with reactive oxygen species (ROS) management through primary and secondary metabolism as adaptive response, on exogenous Cd exposure of W. somnifera. Increased invertase enzyme activity resulted in higher reducing sugars in plant under Cd stress to provide additional carbon source and NADH or NADPH. Higher activities of proline metabolic pathway enzymes such as ornithine aminotransferase (OAT) and pyrroline-5-corboxylate synthase (P5CS) resulted in elevated proline accumulation. The considerable participation of phenylpropanoid metabolism also found dominantly upregulated. Increased enzyme activities of phenylalanine ammonia lyase (PAL), shikimate dehydrogenase (SKDH), glucose-6-phosphate dehydrogenase (G6PDH), and cinnamyl alcohol dehydrogenase (CADH) resulted in phenolics and flavonoids accumulation under higher Cd stress. Upregulation of glutathione-S-transferase (GST) activity conferred its role in Cd chelation. In addition, glutamate oxaloacetate transaminase (GOT), amyl esterase (EST) and diaphorase (DIA) established their participation in Cd tolerance mechanism. Thus, present study elucidated major role of proline and phenylpropanoid metabolism in providing the osmoticum and antioxidants to the plants under Cd stress. The information may be helpful in developing stress resistant plants by targeting these pathways using conventional and molecular approaches.

Relationship between stem characteristics and lodging resistance of Tartary buckwheat (Fagopyrum tataricum)

ABSTRACT Stem lodging can limit the grain yield of Tartary buckwheat (Fagopyrum tataricum), and creates difficulties in harvesting. A 2-year study was conducted to study the relationships between stem characteristics and lodging resistance in Tartary buckwheat. Six Tartary buckwheat cultivars with three stem types (short-stemmed XQ1 and CQ1; mid-length stemmed YQ1 and QK3; and tall-stemmed DAB and DN1) were used. The stem characteristics differed significantly among the three stem types. Mid-length stems had the thickest stem wall, the greatest numbers of large and small vascular bundles, and the lowest stem diameter/stem wall thickness ratio among the three stem types. Mid-length stems had the highest stem breaking strength (SBS) and stem puncture strength (SPS) among the three types of stem. The lignin content was significantly higher in mid-length stems than in tall and short stems. The activities of phenylalanine ammonia-lyase (PAL), tyrosine ammonia-lyase (TAL), and cinnamyl alcohol dehydrogenase (CAD), but not 4-coumarate: CoA ligase (4CL), differed significantly among the three stem types. In correlation analyses, SBS was significantly positively correlated with stem diameter, stem wall thickness, and the number of large and small vascular bundles, but significantly negatively correlated with stem diameter/stem wall thickness and lodging rate. The lignin content was significantly positively correlated with the activities of lignin-related enzymes and with SBS and SPS, and significantly negatively correlated with lodging rate. The present study provides preliminary insights into the relationship between stem traits and lodging resistance in Tartary buckwheat, laying a foundation for a further understanding of lodging resistance. Abbreviations SBS: stem breaking strength; SPS: stem puncture strength; PAL: phenylalanine ammonia-lyase; TAL: tyrosine ammonia-lyase; CAD: cinnamyl alcohol dehydrogenase; 4CL: 4-coumarate: CoA ligase.

Overexpression of cinnamyl alcohol dehydrogenase gene from sweetpotato enhances oxidative stress tolerance in transgenic Arabidopsis

Cinnamyl alcohol dehydrogenase (CAD) is the enzyme in the last step of lignin biosynthetic pathway and is involved in the generation of lignin monomers. IbCAD1 gene in sweetpotato (Ipomoea batatas) was identified, and its expression was induced by abiotic stresses based on promoter analysis. In this study, transgenic Arabidopsis plants overexpressing IbCAD1 directed by CaMV 35S promoter were developed to determine the physiological function of IbCAD1. IbCAD1-overexpressing transgenic plants exhibited better plant growth and higher biomass compared to wild type (WT), under normal growth conditions. CAD activity was increased in leaves and roots of transgenic plants. Sinapyl alcohol dehydrogenase activity was induced to a high level in roots, which suggests that IbCAD1 may regulate biosynthesis of syringyl-type (S) lignin. Lignin content was increased in stems and roots of transgenic plants; this increase was in S lignin rather than guaiacyl (G) lignin. Overexpression of IbCAD1 in Arabidopsis resulted in enhanced seed germination rates and tolerance to reactive oxygen species (ROS), such as hydrogen peroxide (H2O2). Taken together, our results show that IbCAD1 controls lignin content by biosynthesizing S units and plays an important role in plant responses to oxidative stress.

Shade stress decreases stem strength of soybean through restraining lignin biosynthesis

Lodging is the most important constraint for soybean growth at seedling stage in maize-soybean relay strip intercropping system. In the field experiments, three soybean cultivars Nandou 032-4 (shade susceptible cultivar; B1), Jiuyuehuang (moderately shade tolerant cultivar; B2), and Nandou 12 (shade tolerant cultivar; B3) were used to evaluate the relationship between stem stress and lignin metabolism in the stem of soybean. Results showed that the intercropped soybean was in variable light condition throughout the day time and co-growth stage with maize. The xylem area and cross section ratio played a main role to form the stem stress. The B3 both in intercropping and monocropping expressed a high stem stress with higher xylem area, lignin content, and activity of enzymes (phenylalanine ammonia-lyase (PAL), 4-coumarate: CoA ligase (4CL), cinnamyl alcohol dehydrogenase (CAD), and peroxidase (POD)) than those of B1 and B2. Among the soybean cultivars and planting pattern, lignin content was positively correlated with stem stress. However, a negative correlation was found between lignin content and actual rate of lodging. In conclusion, the shade tolerant soybean cultivar had larger xylem area, higher lignin content and activities of CAD, 4CL, PAL, and POD than other soybean cultivars in intercropping. The lodging in maize-soybean intercropping can be minimized by planting shade tolerant and lodging resistant cultivar of soybean. The lignin content in stem could be a useful indicator for the evaluation of lodging resistance of soybean in intercropping and activities of enzymes were the key factors that influence the lignin biosynthesis.

Molecular Mechanism of Xylogenesis in Moso Bamboo (Phyllostachys edulis) Shoots during Cold Storage.

A bamboo shoot is the immature stem of the woody grass and a nutritious and popular vegetable in East Asia. However, it undergoes a rapid xylogenesis process right after harvest, even being stored in a cold chamber. To investigate the molecular regulation mechanisms of xylogenesis in Moso bamboo (Phyllostachys edulis) shoots (MBSes) during cold storage, the measurement of cell wall polymers (cellulose, hemicellulose, and lignin) and related enzyme activities (phenylalanine ammonia lyase (PAL), cinnamyl alcohol dehydrogenase (CAD), peroxidase (POD), and xylan xylosyltransferase (XylT)) and transcriptomic analysis were performed during cold storage. It was noticed that cellulose and lignin contents increased, while hemicellulose content exhibited a downward trend. PAL, CAD, and POD activity presented an upward trend generally in MBS when stored at 4 °C for 16 days. XylT activity showed a descending trend during the stages of storage, but slightly increased during the 8th to 12th days after harvest at 4 °C. Transcriptomic analysis identified 72, 28, 44, and 31 functional unigenes encoding lignin, cellulose, xylan biosynthesis enzymes, and transcription factors (TFs), respectively. Many of these secondary cell wall (SCW)-related genes showed higher expression levels in the later period of cold storage. Quantitative RT-PCR analysis of the selected genes conformed to the expression pattern. Our study provides a comprehensive analysis of MBS secondary wall biosynthesis at the molecular level during the cold storage process. The results give insight into the xylogenesis process of this economically important vegetable and shed light on solving this problem of the post-harvest industry.

Phenolic metabolism and related heavy metal tolerance mechanism in Kandelia Obovata under Cd and Zn stress

In the present study, a set of pot culture experiments was conducted to reveal how the metabolism process of phenolic compounds was affected by cadmium (Cd) and zinc (Zn) and to further uncover heavy metal tolerance mechanisms in Kandelia obovata. After 60d of treatment, the biomass and chlorophyll a content in the leaves were suppressed, but total phenolic compounds in roots and leaves were improved by the increasing gradient of Cd or Zn concentrations; Total phenolic compounds significantly increased by 3.6–44.6% in the roots, and by 0.4–126.6% in the leaves. At the meantime, the activity of Shikimate dehydrogenase (SKDH), cinnamyl alcohol dehydrogenase (CAD), and polyphenol oxidase (PPO) in the roots increased by 11.2–307.6%, 12.4–175.4% and − 2.7–392.8%, and the results were 3.4–69.5%, 1.7–40.0%, 16.0–99.7% in the leaves. Higher toxicity of Cd than Zn, as well as slight alleviating effect of 100 mg kg−1 Zn on 2.5 mg kg−1 Cd were found. Additionally, a significantly positive correlation coefficients for relationship between phenolic metabolism related enzyme activity and Cd/Zn contamination levels was found, and leaf SKDH, leaf CAD, and leaf PPO activities were moderately correlated with leaf Cd (r = 0.39, r = 0.43, and r = 0.57, respectively) and leaf Zn (r = 0.44, r = 0.41, r = 0.19, respectively) content, which indicate that Cd and Zn play a previously unrecognized but major role in phenolic compounds synthesis, transport, and metabolism in K. obovata. The results also provided evidence that the application of high levels of Cd and Zn was accompanied by three phenolic metabolism pathways participating in heavy metal tolerance process.

Lignin synthesis and accumulation in barley cultivars differing in their resistance to lodging

Since lignin greatly affects stem strength, which is an important agronomical trait, understanding the relationship between lodging resistance and lignin synthesis is important in barley breeding and selection processes. The aim of the study was to reveal the connection between physiological aspects of lignin synthesis and genetic background of barley cultivars with different lodging phenotype. Three barley cultivars Astor, Scarlett and Jaran were compared by measuring lignin, cellulose and total soluble phenolics content, phenylalanine ammonia-lyase activity (PAL) and expression of cinnamoyl-CoA reductase (CCR) and cinnamyl-alcohol dehydrogenase (CAD) in three lower internodes at flowering and grain filling stage. To assess their genetic background simple sequence repeats (SSR) markers, connected to lodging resistance and plant height, were analyzed. Compared to lodging susceptible cultivars Scarlett and Jaran, a lodging resistant cultivar Astor revealed different dynamics of lignin synthesis and deposition, showing higher PAL activity and total soluble phenolics content as well as higher expression of CCR and CAD genes in the second internode at grain filling stage. Analysis of SSR markers associated with quantitative trait loci (QTL) for lodging resistance revealed that Astor discriminates from Scarlett and Jaran by marker Bmag337 connected with elongation of the second internode. Lignification process is under a strong influence of genotype and environmental factors which determine lignin synthesis dynamics and deposition of lignin in the cell walls of barley.