Phenylpropanoid metabolism enzyme activities and gene expression in postharvest melons inoculated with Alternaria alternata

This study explored the mechanism of melon resistance to Alternaria alternata (A. alternata) infection in Jiashi and 86-1 melons. Melons were inoculated with A.alternata and the change in lesion diameter was measured. The changes in cinnamic acid-4-hydroxylase (C4H), phenylalanine ammonia lyase (PAL), and 4-coumaric acid coenzyme A ligase (4CL) activity and gene expression were studied in the pericarp tissues of Jiashi and 86-1 melons. The lesion diameter was smaller in Jiashi melon than in 86-1 melon, and the pericarp lesions were smaller than pulp lesions, indicating that Jiashi melon can resist A. alternata infection better than 86-1 melon. After inoculation with A. alternata, the C4H, PAL, and 4CL activities of Jiashi and 86-1 melons peaked in the middle and late storage period, and the peak was higher in Jiashi melons. The gene expression changes were consistent with the enzyme activity. The C4H, PAL, and 4CL gene expression was significantly higher in Jiashi melon pericarp than in 86-1 melon, and the C4H, PAL, and 4CL activities in Jiashi melon were positively correlated with their gene expression, confirming the role of phenylpropanoid metabolism enzymes in resistance to A. alternata.

Biosynthesis of poly(glycolate-co-3-hydroxybutyrate-co-3-hydroxyhexanoate) in Escherichia coli expressing sequence-regulating polyhydroxyalkanoate synthase and medium-chain-length 3-hydroxyalkanoic acid coenzyme A ligase

Chimeric polyhydroxyalkanoate synthase PhaCAR is characterized by the capacity to incorporate unusual glycolate (GL) units and spontaneously synthesize block copolymers. The GL and 3-hydroxybutyrate (3HB) copolymer synthesized by PhaCAR is a random-homo block copolymer, poly(GL-ran-3HB)-b-poly(3HB). In the present study, medium-chain-length 3-hydroxyhexanoate (3HHx) units were incorporated into this copolymer using PhaCAR for the first time. The coenzyme A (CoA) ligase from Pseudomonas oleovorans (AlkK) serves as a simple 3HHx-CoA supplying route in Escherichia coli from exogenously supplemented 3HHx. NMR analyses of the obtained polymers revealed that 3HHx units were randomly connected to 3HB units, whereas GL units were heterogeneously distributed. Therefore, the polymer is composed of two segments: P(3HB-co-3HHx) and P(GL-co-3HB-co-3HHx). The thermal and mechanical properties of the terpolymer indicate no contiguous P(3HB) segments in the material, consistent with the NMR results. Therefore, PhaCAR synthesized the novel block copolymer P(3HB-co-3HHx)-b-P(GL-co-3HB-co-3HHx), which is the first block PHA copolymer comprising two copolymer segments.

Adult-onset adrenoleukodystrophy presenting with status epilepticus and psychosis

Adrenoleukodystrophy (ALD) is an X linked recessive genetic disorder caused by an abnormality in the ABCD1 gene on the X chromosome, that affects 1 in 20 000 people. In X linked adrenoleukodystrophy (X-ALD), a defect in lignoceroyl-coenzyme A ligase causes pathognomonic tissue accumulation of very long chain fatty acids (VLCFA) in the adrenal cortex and nervous system. The phenotypic variability ranges from cerebral inflammatory demyelination of childhood onset, leading to death within 5 years, to adults remaining presymptomatic through more than five decades. Our case is that of a man who was previously diagnosed with bipolar affective disorder presented with dystonic posturing. During transit, he had an episode of generalised convulsive status epilepticus. He presented with spasticity and exaggerated reflexes. Three important signs of adrenal insufficiency were observed: hypotension, hyperpigmentation and comatose state. The diagnosis of X-ALD should be considered in young men presenting with gradually progressive unexplained cognitive and behavioural problems, a strong family history, adrenal insufficiency, bilateral upper motor signs with absent ankle reflexes.

Carbon and nitrogen metabolism under nitrogen variation affects flavonoid accumulation in the leaves of Coreopsis tinctoria

Flavonoids are phytochemicals present in medicinal plants and contribute to human health. Coreopsis tinctoria, a species rich in flavonoids, has long been used in traditional medicine and as a food resource. N (nitrogen) fertilization can reduce flavonoid accumulation in C. tinctoria. However, there is limited knowledge regarding N regulatory mechanisms. The aim of this study was to determine the effect of N availability on flavonoid biosynthesis in C. tinctoria and to investigate the relationship between C (carbon) and N metabolism coupled with flavonoid synthesis under controlled conditions. C. tinctoria seedlings were grown hydroponically under five different N levels (0, 0.625, 1.250, 2.500 and 5.000 mM). The related indexes of C, N and flavonoid metabolism of C. tinctoria under N variation were measured and analysed. N availability (low and moderate N levels) regulates enzyme activities related to C and N metabolism, promotes the accumulation of carbohydrates, reduces N metabolite levels, and enhances the internal C/N balance. The flavonoid content in roots and stalks remained relatively stable, while that in leaves peaked at low or intermediate N levels. Flavonoids are closely related to phenylalanine ammonia-lyase (PAL), cinnamate 4-hydroxylase (C4H), 4-coumarate: coenzyme A ligase (4CL), and chalcone-thioase (CHS) activity, significantly positively correlated with carbohydrates and negatively correlated with N metabolites. Thus, C and N metabolism can not only control the distribution of C in amino acid and carbohydrate biosynthesis pathways but also change the distribution in flavonoid biosynthesis pathways, which also provides meaningful information for maintaining high yields while ensuring the nutritional value of crop plants.

Comparative Transcriptomic Analyses of Chlorogenic Acid Biosynthesis Pathways in Diploid and Triploid Camellia sinensis

Chlorogenic acid (CGA), as a kind of depside in plants, has a variety of beneficial effects on human health, which also plays an important role in helping plants resist a variety of stresses. Therefore, the biosynthetic pathway of CGA has been studied in many plants, however, the synthesis of CGA has not been well elucidated in Camellia sinensis. In our research, different CGA levels were detected between triploid tea variety „Qianfu 4‟ and diplont tea variety „Qianmei 419‟ using HPLC and the CGA content in triploid Camellia sinensis was greater than that in diploid Camellia sinensis. Transcriptome sequencing for diploid and triploid Camellia sinensis was employed to explore genes associated with CGA biosynthesis. Finally, 154,097 unigenes were obtained in total, of which 891 may be related to the biosynthesis of CGA. Furthermore, differentially expressed genes (DEGs) were screened between diploid and triploid Camellia sinensis, 32 DEGs were discovered to be related to CGA biosynthesis, including sixteen phenylalanine ammonia lyase (PAL) genes, three 4-coumarate coenzyme A ligase (4CL) genes, nine cinnamate 4-Hydroxylase (C4H) genes, four Hydroxycinnamoyl-CoA shikimate/quinate hydroxycinnamoyl transferase (HQT/HCT), and two hundred and twenty-one TFs including eighty-eight ERFs, forty-one bZIPs, forty-two MYBs and fifty WRKYs, which may also play an important role in the biosynthesis of CGA. Our results will lay the foundation for further exploration of the biosynthesis of CGA and revealing the related regulatory network in Camellia sinensis. © 2021 Friends Science Publishers

GABA Regulates Phenolics Accumulation in Soybean Sprouts under NaCl Stress

NaCl stress causes oxidative stress in plants; γ-aminobutyric acid (GABA) could alleviate such abiotic stress by enhancing the synthesis of phenolics, but the underlying mechanism is not clear. We investigated the effects of GABA on phenolics accumulation in soybean sprouts under NaCl stress by measuring changes in the content of physiological biochemicals and phenolic substances, in the activity and gene expression of key enzymes, and in antioxidant capacity. GABA reduced the oxidative damage in soybean sprouts caused by NaCl stress and enhanced the content of total phenolics, phenolic acids, and isoflavones by 16.58%, 22.47%, and 3.75%, respectively. It also increased the activities and expression of phenylalanine ammonia lyase, cinnamic acid 4-hydroxylase, and 4-coumarate coenzyme A ligase. Furthermore, GABA increased the activity of antioxidant enzymes and the antioxidant capacity. These events were inhibited by 3-mercaptopropionate (an inhibitor for GABA synthesis), indicating that GABA mediated phenolics accumulation and antioxidant system enhancement in soybean sprouts under NaCl stress.

Nitrogen deficiency maintains the yield and improves the antioxidant activity of Coreopsis tinctoria Nutt

Nitrogen (N) deficiency levels were investigated for their potential to maintain the yield and improve antioxidant activity of Coreopsis tinctoria. Inflorescences and leaves at 0, 10, 20, 30, 40 and 50 d after flowering were frozen at −80 °C and plant growth, antioxidant activity, bioactive substance, enzyme activity and gene expression were evaluated. N deficiency maintained the total number of flowers, promoted phenol and flavonoid accumulation and enhanced antioxidant activity. Moreover, N deficiency stimulated activities of phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H) and 4-coumarate: coenzyme A ligase (4CL) and induced CtPAL, CtC4H and Ct4CL gene expression. The data also suggest that N deficiency-induced phenolic and flavonoid accumulation occurs due to the activation of biosynthetic pathways in C. tinctoria. We characterize the unique features of C. tinctoria under N deficiency conditions and provide valuable information for the cultivation of high-N use efficiency varieties with low input and high output.

BTH Treatment Delays the Senescence of Postharvest Pitaya Fruit in Relation to Enhancing Antioxidant System and Phenylpropanoid Pathway

The plant resistance elicitor Benzo (1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH) can enhance disease resistance of harvested fruit. Nonetheless, it is still unknown whether BTH plays a role in regulating fruit senescence. In this study, exogenous BTH treatment efficiently delayed the senescence of postharvest pitaya fruit with lower lipid peroxidation level. Furthermore, BTH-treated fruit exhibited lower hydrogen peroxide (H2O2) content, higher contents of reduced ascorbic acid (AsA) and reduced glutathione (GSH) levels and higher ratios of reduced to oxidized glutathione (GSH/GSSG) and ascorbic acid (AsA/DHA), as well as higher activities of ROS scavenging enzymes, including superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD) and glutathione reductase (GR) in comparison with control fruit. Moreover, BTH treatment enhanced the activities of phenylpropanoid pathway-related enzymes, including cinnamate-4-hydroxylase (C4H), phenylalanine ammonia-lyase (PAL) and 4-coumarate/coenzyme A ligase (4CL) and the levels of phenolics, flavonoids and lignin. In addition, BTH treatment upregulated the expression of HuSOD1/3/4, HuCAT2, HuAPX1/2 and HuPOD1/2/4 genes. These results suggested that application of BTH delayed the senescence of harvested pitaya fruit in relation to enhanced antioxidant system and phenylpropanoid pathway.