Identification of QTLs Associated with Conversion of Sucrose to Hexose in Mature Fruit of Japanese Pear

Sweetness is the most important trait for fruit breeding and is fundamentally determined by both total and individual sugar contents. We analyzed the contents of sucrose, fructose, glucose, and sorbitol in mature fruit in an F₁ population derived from crossing modern Japanese pear cultivar ‘Akizuki’ and breeding line ‘373-55’. A genetic linkage map was constructed using simple sequence repeats (SSRs) and single-nucleotide polymorphisms (SNP). We identified two regions associated with individual sugar contents on linkage group (LG) 1 and LG 7. The percentages of the variance in sucrose, fructose, and glucose explained by the quantitative trait loci (QTLs) were 26.6, 15.9, and 18.5%, respectively, for the region on LG 1, and 22.2, 20.0, and 9.5%, respectively, for the region on LG 7. In both regions, genotypes associated with increases in sucrose were associated with decreases in both fructose and glucose. The 1.5-LOD support intervals of the QTLs on LGs 1 and 7 include SSRs within the regions flanking acid invertase genes PPAIV3 and PPAIV1, respectively. Because acid invertase is a key enzyme in the conversion of sucrose to hexose, these are promising candidates for genes underlying those QTLs and controlling individual sugar contents. We also found one region on LG 11 that explained 21.4% of the variation in total sugar content but was not significantly associated with variation for individual sugars. The information obtained in this study will accelerate research and breeding programs to improve fruit sweetness.     

Differential expression of a fructose receptor gene in honey bee workers according to age and behavioral role

Honey bee (Apis mellifera) workers contribute to the maintenance of colonies in various ways. The primary functions of workers are divided into two types depending on age: young workers (nurses) primarily engage in such behaviors as cleaning and food handling within the hive, whereas older workers (foragers) acquire floral nutrients beyond the colony. Concomitant with this age‐dependent change in activity, physiological changes occur in the tissues and organs of workers. Nurses supply younger larvae with honey containing high levels of glucose and supply older larvae with honey containing high levels of fructose. Given that nurses must determine both the concentration and type of sugar used in honey, gustatory receptors (Gr) expressed in the chemosensory organs likely play a role in distinguishing between sugars. Glucose is recognized by Gr1 in honey bees (AmGr1); however, it remains unclear which Gr are responsible for fructose recognition. This study aimed to identify fructose receptors in honey bees and reported that AmGr3, when transiently expressed in Xenopus oocytes, responded only to fructose, and to no other sugars. We analyzed expression levels of AmGr3 to identify which tissues and organs of workers are involved in fructose recognition and determined that expression of AmGr3 was particularly high in the antennae and legs of nurses. Our results suggest that nurses use their antennae and legs to recognize fructose, and that AmGr3 functions as an accurate nutrient sensor used to maintain food quality in honey bee hives.     

Fluoroquinolones and propionic acid derivatives induce inflammatory responses in vitro

Fluoroquinolones and propionic acid derivatives are widely used antibacterials and non-steroidal anti-inflammatory drugs, respectively, which have been reported to frequently trigger drug hypersensitivity reactions. Such reactions are induced by inflammatory mediators such as cytokines and chemokines. The present study investigated whether levofloxacin, a fluoroquinolone, and loxoprofen, a propionic acid derivative, have the potential to induce immune-related gene expression in dendritic cell-like cell lines such as HL-60, K562, and THP-1, and immortalized keratinocytes such as HaCaT. The expression of IL-8, MCP-1, and TNFα messenger RNA (mRNA) was found to increase following treatment with levofloxacin or loxoprofen in HL-60 cells. In addition, these drugs increased the mRNA content of annexin A1, a factor related to keratinocyte necroptosis in patients with severe cutaneous adverse reactions. Inhibition studies using specific inhibitors of mitogen-activated protein (MAP) kinases and NF-κB suggest that the extracellular signal-regulated kinase (ERK) pathway is the pathway principally involved in the induction of cytokines and annexin A1 by levofloxacin, whereas the involvement of MAP kinases and NF-κB in the loxoprofen-induced gene expression of these factors may be limited. Fluoroquinolones and propionic acid derivatives that are structurally related to levofloxacin and loxoprofen, respectively, were also found to induce immune-related gene expression in HL-60 cells. Collectively, these results suggest that fluoroquinolones and propionic acid derivatives have the potential to induce the expression of immune-related factors and that an in vitro cell-based assay system to detect the immune-stimulating potential of systemic drugs might be useful for assessing the risk of drug hypersensitivity reactions.     

Respiratory stimulation and generation of superoxide radicals in Pseudomonas aeruginosa by fungal naphthoquinones

The mechanism of action of antimicrobial naphthoquinones from the fungus Fusarium was studied by using Pseudomonas aeruginosa. Bostricoidin, methyl ether fusarubin, and fusarubin stimulated the oxygen consumption of bacterial cells and induced cyanide-insensitive oxygen consumption. These activities of the tested compounds were also observed in bacterial membrane preparations in a dose-dependent manner. Naphthoquinones stimulated the generation of superoxide anion and hydrogen peroxide. The naphthoquinone effectively acted as the electron acceptors for bacterial diaphorase, which could explain the antibacterial activity of Fusarium naphthoquinones since electron acceptors lead to the stimulation of respiratory activity and the generation of oxygen radical species. Received: 12 July 1996 / Accepted: 31 October 1996     

Isolation of D-4-chlorotryptophane derivatives as auxin-related metabolites from immature seeds of Pisum sativum

Summary Three active compounds which induce hypocotyl swelling in Phaseolus mungo were isolated from immature seeds of Pisum sativum. For purification of the compounds, our three-step procedure (counter-current distribution, Sephadex LH 20, and partition chromatography on silicic acid) were used. The chemical structures of two of the compounds were determined by synthesis to be -N-carboethoxyacetyl- and -N-carbomethoxyacetyl-D-4-chlorotryptophane. D-4-Chlorotryptophane is the first naturally occurring chlorinated amino acid found.     

Essential roles of high-mobility group box 1 in the development of murine colitis and colitis-associated cancer

High-mobility group box 1 (HMGB1) is a nuclear factor released extracellularly as a proinflammatory cytokine. We measured the HMGB1 concentration in the sera of mice with chemically induced colitis (DSS; dextran sulfate sodium salt) and found a marked increase. Inhibition of HMGB1 by neutralizing anti-HMGB1 antibody resulted in reduced inflammation in DSS-treated colons. In macrophages, HMGB1 induces several proinflammatory cytokines, such as IL-6, which are regulated by NF-kappaB activation. Two putative sources of HMGB1 were explored: in one, bacterial factors induce HMGB1 secretion from macrophages and in the other, necrotic epithelial cells directly release HMGB1. LPS induced a small amount of HMGB1 in macrophages, but macrophages incubated with supernatant prepared from necrotic cells and containing large amounts of HMGB1 activated NF-kappaB and induced IL-6. Using the colitis-associated cancer model, we demonstrated that neutralizing anti-HMGB1 antibody decreases tumor incidence and size. These observations suggest that HMGB1 is a potentially useful target for IBD treatment and the prevention of colitis-associated cancer.     

Constituents of Aristolochia cinnabarina

Nine compounds, aristolochic acid (1), aristolochic acid- Ⅱ (2), aristolochic acid- Ⅲ a (3), aristoloside (4), aristolactam-N-β-D-glucoside (5), aristolactam-β-D-glucoside (6), tuberosinone (7), tuberosinone N-β-D-glucoside (8) and 6-O-p-coumaroyl-D-glucopyranose (9), were isolated from methanol extracts of fresh roots of Aristolochia cinnabarina. Among them, compound 9 was reported in Aristolochiaceae for the first time.