Carbohydrate metabolism during fruit development in sweet pepper (Capsicum annuum) plants

Growth, accumulation of sugars and starch, and the activity of enzymes involved in sucrose mobilization were determined throughout the development of sweet pepper fruits. Fruit development was roughly divided into three phases: (1) an initial phase with high relative growth rate and hexose accumulation, (2) a phase with declining growth rate and accumulation of sucrose and starch, and (3) a ripening phase with no further fresh weight increase and with accumulation of hexoses, while sucrose and starch were degraded. Acid and neutral invertase (EC 3.2.1.26) were closely correlated to relative growth rate until ripening and inversly correlated to the accumulation of sucrose. Acid invertase specifically increased during ripening, concurrently with the accumulation of hexoses. Sucrose synthase (EC 2.4.1.13) showed little correlation to fruit development, and in periods of rapid growth the activity of sucrose synthase was low compared to the invertases. However, during late fruit growth sucose synthase was more active than the invertases. We conclude that invertase activities determine the accumulation of assimilates in the very young fruits, and a reactivation of acid invertase is responsible for the accumulation of hexoses during ripening. During late fruit growth, before ripening, sucrose synthase is transiently responsible for the sucrose breakdown in the fruit tissue. Results also indicate that pyrophosphate-dependent phosphofructokinase (EC 2.7.1.90) and its activator fructose-2,6-bisphosphate (Fru2,6bisP) are involved in the regulation of the sink metabolism of the fruit tissue.     

Carbohydrate metabolism during early fruit development of sweet melon (Cucumis melo)

In sink tissues of cucurbits, including sweet melon fruits, the galactosyl-sucrose oligosaccharides, stachyose and raffinose, together with sucrose, are the major translocated carbohydrates. In the present study we investigated the carbohydrate metabolism of young melon ( Cucumis melo L. cv. C-8) fruit during the period of initial fruit set and development, from 3 days prior to anthesis until 20 days after anthesis (DAA), prior to the onset of sucrose accumulation. The enzymes assayed could be classified into two categories according to developmental patterns. Two of the enzymes, alkaline α -galactosidase I [EC 3.2.1.22], which hydrolyzes both raffinose and stachyose, and acid invertase [EC 3.2.1.26] either increased or remained stable during the first 10 DAA. The remaining measured enzymes (the stachyose-specific alkaline α -galactosidase form II, acid α -galactosidase, alkaline invertase, sucrose synthase [EC 2.4.1.13], galactokinase [EC 2.7.1.6], UDP-Gal PPase [EC 2.7.7.10], UDP-Glc-4 epimerase [EC 5.1.3.2], UDP-Glc PPase [EC 2.7.7.9], phosphoglucomutase [EC 5.4.2.2] and phosphoglucoisomerase [EC 5.3.1.9]) all showed a similar developmental pattern of steady decrease in activity following anthesis. We also compared the saccharide metabolism of pollinated and non-pollinated ovaries during the initial days following anthesis. In the absence of pollination, ovary growth dramatically decreased by the first DAA and was accompanied by a sharp decrease in the activity of UDP-Glc PPase. Other enzymes in the pathway, including the enzymes of stachyose and raffinose hydrolysis, did not decrease in activity until 2 or 4 DAA, after ovary growth was affected. These results provide information to assess the possible regulating enzymes in cucurbit ovary development and fruit set.     

The food of sweet and bitter fancy

The MAP30 ribosomal inactivating protein structure has been determined by NMR spectroscopy. This anti-HIV and anti-cancer protein is an RNA and DNA glycosylase as well as a DNA apurinic/apyrimidinic (AP) lyase.     

Expression pattern of ABA metabolic and signalling genes during floral development and fruit set in sweet cherry

Abscisic acid plays a crucial role in the regulation of fruit development and ripening, however, its role in the floral development and the fruit set is still unclear. In the present study, the ABA accumulation and the expression patterns of genes related to ABA metabolism and signalling in sweet cherry were investigated. The results showed that ABA accumulation increased and peaked at stage V in ovary, at stage VI in stamen, and in young fruit it peaked at 7 days after full bloom. The expression pattern of ABA synthetase PaNCED1 was consistent with the changes of ABA accumulation. Among four ABA degradation enzymes PaCYP707As, PaCYP707A4 was highly expressed in ovary, PaCYP707A1 was mainly in stamen, and PaCYP707A2 was in young fruit, and their expressions were reversed to the trend of PaNCED1. With regard to ABA signalling genes, among three ABA receptors PaPYLs, PaPYL2 and PaPYL3 were high expression genes in ovary and in young fruit with similar expression patterns, while PaPYL3 was the high expression gene in stamen. Within six PaPP2Cs, PaPP2C1/2/3 were highly expressed in ovary and young fruit, while PaPP2C3/4 were mainly in stamen. The six PaSnRK2s showed different expression patterns: PaSnRK2.1/2.2/2.4 were highly expressed in ovary and young fruit, while PaSnRK2.1/2.3 were highly expressed in stamen. In situ hybridization results showed that PaPYL3, PaPP2C3 and PaSnRK2.4 were expressed in seed, pulp and fruit peel during fruit set. In conclusion, ABA and its signaling may play an important role in the regulation of floral development and fruit set.     

The sweet and the bitter of mammalian taste

The discovery of two families of mammalian taste receptors has provided important insights into taste recognition and taste perception. Recent studies have examined the receptors and signaling pathways that mediate sweet, bitter, and amino acid taste detection in mammals. These studies demonstrate that taste cells are selectively tuned to different taste modalities and clarify the logic of taste coding in the periphery.     

The sweet and bitter sides of galectins in melanoma progression

Melanoma is the leading cause of skin cancer-related deaths, which is due in large part to its aggressive behavior, resistance to therapy, and ability to metastasize to multiple organs such as the lymph nodes, lung, and brain. Melanoma progresses in a stepwise manner from the benign nevus, to radial spreading through the dermis, to a vertical invasive phase, and finally to metastasis. The carbohydrate-binding family of galectins has a strong influence on each phase of melanoma progression through their effects on immune surveillance, angiogenesis, cell migration, tumor cell adhesion, and the cellular response to chemotherapy. Galectins share significant homology in their carbohydrate recognition domain (CRD), which mediates binding to an array of N-glycosylated proteins located on the surface of tumor cells, endothelial cells, T-cells, and to similarly glycosylated extracellular matrix proteins. Galectins are also present within tumor cells where they perform anti-apoptotic functions and enhance intracellular signaling that results in deregulated expression of genes involved in tumor progression. The most extensively studied galectins, galectin-1 and galectin-3, have been shown to have profound effects on melanoma growth and metastasis by influencing many of these biological processes.     

Xyloglucan endotransglucosylase/hydrolases (XTHs) during tomato fruit growth and ripening

Depolymerization of cell wall xyloglucan has been proposed to be involved in tomato fruit softening, along with the xyloglucan modifying enzymes. Xyloglucan endotransglucosylase/hydrolases (XTHs: EC 2.4.1.207 and/or EC 3.2.1.151) have been proposed to have a dual role integrating newly secreted xyloglucan chains into an existing wall-bound xyloglucan, or restructuring the existing cell wall material by catalyzing transglucosylation between previously wall-bound xyloglucan molecules. Here, 10 tomato (Solanum lycopersicum) SlXTHs were studied and grouped into three phylogenetic groups to determine which members of each family were expressed during fruit growth and fruit ripening, and the ways in which the expression of different SlXTHs contributed to the total XET and XEH activities. Our results showed that all of the SlXTHs studied were expressed during fruit growth and ripening, and that the expression of all the SlXTHs in Group 1 was clearly related to fruit growth, as were SlXTH12 in Group 2 and SlXTH6 in Group 3-B. Only the expression of SlXTH5 and SlXTH8 from Group 3-A was clearly associated with fruit ripening, although all 10 of the different SlXTHs were expressed at the red ripe stage. Both total XET and XEH activities were higher during fruit growth, and decreased during fruit ripening. Ethylene production during tomato fruit growth was low and experienced a significant increase during fruit ripening, which was not correlated either with SlXTH expression or with XET and XEH activities. We suggest that the role of XTH during fruit development could be related to the maintenance of the structural integrity of the cell wall, and the decrease in XTHs expression, and the subsequent decrease in activity during ripening may contribute to fruit softening, with this process being regulated through different XTH genes.     

Effects of the bitter additives naringin and sucrose octa-acetate on sweet persistence and sweet quality of neohesperidin dihydrochalcone

The maximal perceived sweet intensity (Ip_max) and the sweetpersistence constant (T) of neohesperidin dihydrochalcone (NHD),were significantly reduced in a mixture containing naringin(NAR), a bitter flavone analog of NHD Sucrose octa-acetate (SOA),another bitter stimulus, reduced the Ip_max of NHD in mixtures,but no appreciable decrease in T values was found. Linear regressionanalyses performed on the IP_max data of either NHD + NAR orNHD + SOA (logIp_max versus log concentration) produced slopevalues lower than those of NHD alone. Moreover, taste similarityexperiments revealed that the mixture of NHD + NAR was locatedfurther than NHD from the sugar area in the multi-dimensionalscaling (MDS) map. It is concluded that the reduction in Tvaluesof NHD by NAR was apparently related to the reduced Ip_max levelsand that such a mixture produces a sweet quality inferior tothat of NHD.     

Chronic obstructive pulmonary disease and glucose metabolism: a bitter sweet symphony

Chronic obstructive pulmonary disease, metabolic syndrome and diabetes mellitus are common and underdiagnosed medical conditions. It was predicted that chronic obstructive pulmonary disease will be the third leading cause of death worldwide by 2020. The healthcare burden of this disease is even greater if we consider the significant impact of chronic obstructive pulmonary disease on the cardiovascular morbidity and mortality. Chronic obstructive pulmonary disease may be considered as a novel risk factor for new onset type 2 diabetes mellitus via multiple pathophysiological alterations such as: inflammation and oxidative stress, insulin resistance, weight gain and alterations in metabolism of adipokines. On the other hand, diabetes may act as an independent factor, negatively affecting pulmonary structure and function. Diabetes is associated with an increased risk of pulmonary infections, disease exacerbations and worsened COPD outcomes. On the top of that, coexistent OSA may increase the risk for type 2 DM in some individuals. The current scientific data necessitate a greater outlook on chronic obstructive pulmonary disease and chronic obstructive pulmonary disease may be viewed as a risk factor for the new onset type 2 diabetes mellitus. Conversely, both types of diabetes mellitus should be viewed as strong contributing factors for the development of obstructive lung disease. Such approach can potentially improve the outcomes and medical control for both conditions, and, thus, decrease the healthcare burden of these major medical problems.     

The pharmacology and signaling of bitter, sweet, and umami taste sensing

Over the last decade, many of the molecular components that mediate the transduction of taste signaling have been elucidated. The chemosensory receptors for taste have been identified as G protein-coupled receptors (GPCRs) and ion channels that are expressed on the surface of highly specialized taste sensory cells. Tastant molecules act as agonists, binding to and stabilizing active conformations of receptors, resulting in the initiation of signal transduction cascades. Taste signaling, therefore, should be amenable to the methods of pharmacology. This review focuses on the GPCR-mediated signaling of bitter, sweet, and umami tastes and emphasizes the opportunities for pharmacologic evaluation.     

Trpm5 null mice respond to bitter, sweet, and umami compounds

Trpm5 is a calcium-activated cation channel expressed selectively in taste receptor cells. A previous study reported that mice with an internal deletion of Trpm5, lacking exons 15-19 encoding transmembrane segments 1-5, showed no taste-mediated responses to bitter, sweet, and umami compounds. We independently generated knockout mice null for Trpm5 protein expression due to deletion of Trpm5's promoter region and exons 1-4 (including the translation start site). We examined the taste-mediated responses of Trpm5 null mice and wild-type (WT) mice using three procedures: gustatory nerve recording [chorda tympani (CT) and glossopharyngeal (NG) nerves], initial lick responses, and 24-h two-bottle preference tests. With bitter compounds, the Trpm5 null mice showed reduced, but not abolished, avoidance (as indicated by licking responses and preference ratios higher than those of WT), a normal CT response, and a greatly diminished NG response. With sweet compounds, Trpm5 null mice showed no licking response, a diminished preference ratio, and absent or greatly reduced nerve responses. With umami compounds, Trpm5 null mice showed no licking response, a diminished preference ratio, a normal NG response, and a greatly diminished CT response. Our results demonstrate that the consequences of eliminating Trmp5 expression vary depending upon the taste quality and the lingual taste field examined. Thus, while Trpm5 is an important factor in many taste responses, its absence does not eliminate all taste responses. We conclude that Trpm5-dependent and Trpm5-independent pathways underlie bitter, sweet, and umami tastes.     

发育期火龙果内参基因的筛选和验证

[目的]筛选火龙果果实发育期稳定表达的内参基因。[方法]以火龙果不同发育时期的果实为材料,利用qRT-PCR技术检测17个看家基因的表达水平,借助ge Norm和Norm Finder筛选出果实发育期理想的内参基因。[结果]Ge Norm评估YLS8和ACT并列排名第一,表达稳定值均为0. 221,配对差异值V_2/3为0. 105; Norm Finder排名前两名为TBP2和YLS8,表达稳定值为0. 160和0. 191。使用内参基因YLS8和TBP2分析火龙果甜菜色素合成途径关键基因HpCytP450-like1的表达水平,与基因Hp Cyt P450-like1在火龙果果实发育期表达趋势一致。[结论]从17个候选基因中筛选出2个理想的的内参基因YLS8和TBP2,可作为火龙果果实发育期相关基因的表达调控研究。     

Studies on water transport through the sweet cherry fruit surface: II. Conductance of the cuticle in relation to fruit development

Water conductance of the cuticular membrane (CM) of sweet cherry (Prunus avium L. cv. Sam) fruit during stages II and III (31-78 days after full bloom, DAFB) was investigated by gravimetrically monitoring water loss through segments of the exocarp. Segments were mounted in stainless-steel diffusion cells, filled with 0.5 ml of deionized water and incubated for 8 h at 25 +/- 2 degrees C over dry silica. Conductance was calculated by dividing the amount of water transpired per unit surface area and time by the difference in water vapor concentration across the segment (23.07 g m(-3) at 25 degrees C). Fruit mass and fruit surface area increased 4.9- and 2.8-fold between 31 and 78 DAFB, respectively. However, CM mass per unit area decreased from 3.9 to 1.5 g m(-2) and percentage of total wax content remained constant at about 31%. Stomatal density decreased from 0.8 to 0.2 mm(-2) (31-78 DAFB). Total conductance of the CM on the fruit cheek (gtot.) remained constant during stage II of development (approx. 1.38 x 10(-4) m s(-1) from 31 to 37 DAFB), increased to 1.73 x 10(-4) m s(-1) during early stage III of fruit growth (43-64 DAFB) then decreased to 0.95 x 10(-4) m s(-1) at maturity (78 DAFB). Partitioning gtot. into cuticular (gcut.) and stomatal conductance (gsto.) revealed that the relative contribution of gcut. to gtot. increased linearly from 30% to 87% of gtot. between 31 and 78 DAFB. respectively. On a whole-fruit basis, g,tot. and gcut. consistently increased up to 64 DAFB, and decreased thereafter. A significant negative linear relationship was obtained between gcut. and CM thickness, but not between the permeability coefficient (p) and CM thickness. Further, p was positively related to strain rate, suggesting that strain associated with expansion of the fruit surface increased p.