Effect and Mechanism of L-Arginine against Alternaria Fruit Rot in Postharvest Blueberry Fruit.

This study aimed to explore the impact of L-arginine (Arg) on the development of resistance to Alternaria tenuissima (A. tenuissima) in blueberries. The metabolism of reactive oxygen species, pathogenesis-related proteins (PRs), and jasmonic acid (JA) biosynthesis pathways were analyzed, including changes in activity and gene expression of key enzymes. The results indicated that Arg treatment could prevent the development of Alternaria fruit rot in postharvest blueberries. In addition, it was also found to induce a burst of hydrogen peroxide in the blueberries early on during storage, thereby improving their resistance to A. tenuissima. Arg treatment was observed to increase the activity of antioxidant enzymes (peroxidase, catalase, superoxide dismutase, and ascorbate peroxidase) and related gene expression, as well as the total levels of phenolics, flavonoids, and anthocyanin in the blueberries. The activity and gene expression of the PRs (chitinase and ß-1,3-glucanase) were elevated in Arg-treated blueberries, boosting their resistance to pathogens. Additionally, a surge in endogenous JA content was detected in Arg-treated blueberries, along with upregulated expression of key genes related the JA biosynthesis pathway (VcLOX1, VcAOS1, VcAOC, VcAOC3, VcOPR1, VcOPR3, VcMYC2, and VcCOI1), thereby further bolstering disease resistance. In conclusion, Arg treatment was determined to be a promising prospective method for controlling Alternaria fruit rot in blueberries.

l-Arginine treatment maintains postharvest quality in blueberry fruit by enhancing antioxidant capacity during storage.

The postharvest quality of blueberry fruit is largely limited by deterioration. l-arginine (Arg) is a functional nontoxic amino acid with high biological activities. This study investigated the positive effects and the underlying mechanism of Arg treatment on the quality of postharvest blueberries. Arg effectively mitigated fruit decay and improved the quality of blueberries, including weight loss, firmness, and soluble solid content. Mechanistically, Arg-mediated activation of the anti-oxidative defense system reduced reactive oxygen species-mediated oxidative damage. Moreover, Arg treatment decreased the activities and gene expression of phospholipase D, lipoxygenase, and lipase-inhibiting membrane lipid peroxidation during the prolonged storage of blueberries. Meanwhile, Arg treatment increased nitric oxide (NO) content and NO synthase activity. Furthermore, correlation and principal component analyses revealed the enhancement of Arg treatment on antioxidant capacity. This study suggests that Arg treatment can maintain the postharvest quality of blueberries by improving antioxidant capacity.

Cyanidin-3-O-glucoside Induces Apoptosis and Inhibits Migration of Tumor Necrosis Factor-α-Treated Rat Aortic Smooth Muscle Cells.

Blueberries are rich in anthocyanins (ACNs), which have recently been noted to protect against atherosclerosis development in mice. Cyanidin-3-O-glucoside (C3G), a member of blueberry ACN family, can inhibit the tumor necrosis factor-α (TNF-α)-induced proliferation of vascular smooth muscle cells (VSMCs). However, the effects of C3G on VSMC apoptosis and migration remain unclear. This study was thus conducted to examine whether and how C3G affected the apoptosis and migration of rat aortic smooth muscle cells (RASMCs) challenged by TNF-α. Primary cultured RASMCs were pretreated with C3G (25, 50 or 100 µM) for 2 h and then stimulated with TNF-α (10 ng/ml) for additional 24 h. Our results illustrated that C3G pretreatment induced significant apoptosis in TNF-α-stimulated RASMCs in a dose-dependent way, which was accompanied with increased cleaved caspase-3, caspase-9 and Bax and decreased Bcl-2. Moreover, RASMC migration was enhanced by TNF-α, but markedly suppressed by C3G pretreatment. The expressions and activities of matrix metalloproteinase-2 (MMP-2) and MMP-9 were inhibited by C3G. In addition, TNF-α-enhanced nuclear translocation of nuclear factor kappa B (NF-κB) subunit p65 and phosphorylation of NF-κB inhibitor α (IκBα) in RASMCs were attenuated by C3G. In summary, our study reveals that C3G can induce significant apoptosis in TNF-α-treated RASMCs and markedly inhibit their migration.

Cyanidin-3-O-glucoside attenuates acute lung injury in sepsis rats.

BACKGROUND: Sepsis is a complex syndrome with high mortality, which often induces acute lung injury (ALI) and acute respiratory distress syndrome. Cyanidin-3-O-glucoside (C3G), the most active anthocyanin in the blueberry extracts, has been demonstrated to have pulmonary protective effects in some ALI models. This study aims to evaluate the potential protective effect of C3G on sepsis-evoked ALI in rats. MATERIALS AND METHODS: Cecal ligation and puncture (CLP) was performed on Sprague-Dawley rats to establish sepsis-induced ALI model. Rats were injected intraperitoneally with 10 or 30 mg/kg of C3G after CLP and then the survival was recorded every 12 h for 96 h. The pulmonary protective effects of C3G on CLP-induced ALI were evaluated at 24 h after CLP. RESULTS: The results demonstrated that C3G treatment significantly improved the survival rate of CLP rats and attenuated CLP-induced lung injury, including reduction of lung wet/dry weight ratio, protein leak, infiltration of leukocytes, and myeloperoxidase activity. In addition, C3G markedly decreased malondialdehyde content and increased superoxide dismutase activity and glutathione level. Serum levels of tumor necrosis factor-α, interleukin-1ß, and interleukin-6 were also decreased by C3G administration, as well as protein expression of cyclooxygenase-2 and production of prostaglandin E2 in the lung. Furthermore, C3G treatment upregulated protein expression of inhibitors of NF-κBα and downregulated expressions of nuclear factor kappa-B (NF-κB) p65 and p-p65 in the lung, thereby inhibiting the NF-κB-DNA binding activity. CONCLUSIONS: These findings indicate that C3G exerts pulmonary protective effects on CLP-induced ALI rats. The effect may be associated with NF-κB signaling pathway suppression.

Improved biovar test for Ralstonia solanacearum.

Race 3, biovar 2 strains of Ralstonia solanacearum are quarantined pathogens in Europe and Canada and Select Agent pathogens in the United States. The biovar classification of R. solanacearum strains is based on their biochemical abilities to utilize a carbohydrate panel. The standard biovar test uses bromothymol blue as a pH indicator in 15 ml culture tubes containing 3 to 5 ml of test media, and takes weeks to complete at 24 or 28 °C. We improved the biovar test by using phenol red as a pH indicator that changes color at a higher pH when a carbohydrate is utilized. We also conducted the test at 32 °C in 0.2 ml of 8-tube strips that reduced the medium needed by at least 20 fold. Using the improved test, biovars of R. solanacearum strains can be determined in 4 days when a panel of seven carbohydrates is used including glucose, trehalose, mannitol, sorbitol, dulcitol, maltose and cellobiose. To differentiate biovars 1, 2, 3 and 4, the test can be further simplified and completed in 3 days using a panel of four carbohydrates containing glucose, trehalose, maltose and dulcitol, significantly saving money, space and time.