Sugars induce anthocyanin accumulation and flavanone 3-hydroxylase expression in grape berries

Flavanone 3-hydroxylase (EC 1.14.11.9, F3H) plays a key role in anthocyanin biosynthesis, and sugars enhance anthocyanin accumulation and F3H expression in some other plants. However, information about the relationship between sugars, anthocyanin accumulation and F3H expression in grape berries has been little reported. Present experiment was done with sliced grape berry system. The optimum fruit developmental stage, sugar concentration, and incubation time in sugar induction anthocyanin accumulation and F3H expression were determined. Mannose and 2-deoxyglucose, glucose analogs known to be phosphorylated by hexokinase but are poorly metabolized, obviously induced the anthocyanin accumulation and F3H expression, whereas 3-O-methylglucose and 6-deoxyglucose, glucose analogs transported inside the cell but not substrates for hexokinase, did not induce them. Glucosamine and mannoheptulose, the specific inhibitors of hexokinase, blocked the activation induced by sugar on both anthocyanin accumulation and F3H expression.     

Aphanogmus sp. (Hymenoptera: Ceraphronidae): a hyperparasitoid of the coffee berry borer parasitoid Prorops nasuta (Hymenoptera: Bethylidae) in Kenya

This is the first report of a hyperparasitoid of Prorops nasuta, a primary parasitoid of the coffee berry borer. Aphanogmus sp. is a gregarious ectoparasitoid of larval and pupal stages of P. nasuta, which was found in coffee berry samples collected on the ground of an organic coffee plantation in Western Kenya. The hyperparasitoid shows a clear pattern of emergence from year to year, following its host. Aphanogmus sp. parasitizes around 10% of P. nasuta immature stages under field conditions.     

我国东北高寒地区野生浆果资源研究与利用

经1987～1989年、2002—2003年和近几年的调查,明确了我国东北高寒地区有野生浆果种质资源8个科、13个属、28个种,该区独特的地理条件蕴育了丰富的野生浆果资源,其果实可鲜食,但大部分做为生产果酒、果酱、果汁等的原料,鲜果和加工产品以其丰富的营养、新颖的风味以及纯天然、无污染等独特的优势,被国内外果树生产、科研和消费者所关注。简述其分布、生态环境、开发利用现状及提出对该区野生浆果资源研究开发利的建议。旨在为我国东北高寒地区野生浆果资源的进一步研究及开发利用供依据。     

Agroforestry management affects coffee pests contingent on season and developmental stage

1 Management of vegetational diversity in agroecosystems is a potentially regulating factor of pest population dynamics and may affect developmental stages in different ways.
2 We investigated the population dynamics of red spider mites, coffee leaf miners, and coffee berry borers in three management types of coffee agroforests: increasing plant diversity from a few shade tree species (simple-shade agroforests), intermediate-shade tree species (complex-shade agroforests) to high-shade tree species (abandoned coffee agroforests) in Ecuador. Furthermore, we studied how changes in agroforestry management affect population stage structure of each coffee pest.
3 Our results show that agroforestry management affected seasonal patterns of coffee pests in that higher densities of red spider mites were observed from August to December, coffee leaf miners from December to February, and coffee berry borers from May to July. Moreover, specific developmental stages of red spider mites, coffee leaf miners, and coffee berry borers differed in their responses to agroforestry management. During all stages, red spider mite reached higher densities in simple-shade agroforests compared with complex-shade and abandoned agroforests. Meanwhile, coffee leaf miner densities decreased from simple-shade to complex-shade and abandoned agroforests, but only for larvae, not pupae. Similarly, only coffee berry borer adults (but not eggs, larvae and pupae) demonstrated a response to agroforestry management. Environmental variables characterizing each agroforestry type proved to be important drivers of pest population densities in the field.
4 We emphasize the importance of considering seasonal differences and population structure while investigating arthropod responses to different habitat types because responses change with time and developmental stages.     

Antisense suppression of tomato endo-1,4-β-glucanase Cel2 mRNA accumulation increases the force required to break fruit abscission zones but does not affect fruit softening

Plants of tomato (Lycopersicon esculentum Mill. cv. T5) were transformed with an antisense endo-1,4--glucanase (cellulase, EC 3.2.1.4) Cel2 transgene under the control of the constitutive cauliflower mosaic virus 35S promoter in order to suppress mRNA accumulation of Cel2. In two independent transgenic lines, Cel2 mRNA abundance was reduced by >95% in ripe fruit pericarp and ca. 80% in fruit abscission zones relative to non-transgenic controls. In both transgenic lines the softening of antisense Cel2 fruit pericarp measured using stress-relaxation analysis was indistinguishable from control fruit. No differences in ethylene evolution were observed between fruit of control and antisense Cel2 genotypes. However, in fruit abscission zones the suppression of Cel2 mRNA accumulation caused a significant (P<0.001) increase in the force required to cause breakage of the abscission zone at 4 days post breaker, an increase of 27% in one transgenic line and of 46% in the other transgenic line. Thus the Cel2 gene product contributes to cell wall disassembly occurring in cell separation during fruit abscission, but its role, if any, in softening or textural changes occurring in fruit pericarp during ripening was not revealed by suppression of Cel2 gene expression.     

Immunogold localization of trans-zeatin riboside in embryo and endosperm during early fruit drop of Malus domestica

The specificity of a monoclonal antibody IgG1, raised against trans-zeatin riboside-keyhole limpet hemocyanin conjugate, was investigated by means of inhibition experiments with soluble competing antigens. A competitive enzyme immunoassay was set up, with immobilized antigen. The analysis of the cross reaction profile enabled a study of the specificity of the antigen-antibody interaction. The antibody was able to distinguish the trans form of zeatin riboside from the cis form (cross reaction index = 1 %); cross reactions with ribose, adenine, adenosine and other related heterologous antigens were not detectable over the range of concetration tested. The recognition centres for the antibody seem to be the purine ring and the R substituent, especially in its hydroxymethyl group. Employment of this monoclonal antibody to localize cytokinins in control and shedding affected fruits of Malus domestica Borkh. evidenced high content of trans-zeatin riboside in developing seeds, differences in its content in embryo and endosperm, and a strong reduction of its content in the tissues of drop fruits. This decrease may be an important component responsible for early fruit abscission. This revised version was published online in July 2006 with corrections to the Cover Date.     

Involvement of abscisic acid and ethylene in the responses of citrus seedlings to salt shock

The responses of salt‐sensitive citrus rootstocks to 200 m M NaCl were periodically determined on seedlings of citrange Carrizo ( Citrus sinensis [L.] Osbeck × Poncirus trifoliata [L.] Raf) during 30 days. The stressed seedlings adjusted osmotically, reduced stomatal conductance, increased proline content and ethylene production, and showed massive leaf abscission (92%). The salt shock also increased abscisic acid (ABA) and aminocyclopropane‐1‐carboxylic acid (ACC) in roots, xylem fluid and leaves, and in addition promoted Cl⁻ accumulation. The pattern of change of ABA, ACC and proline followed a two‐phase response: an initial transient increase (10‐12 days) overlapping with a gradual and continuous accumulation. This biphasic response appears to be compatible with the proposal that the transitory hormonal rises are induced by the osmotic component of salinity, whereas the Cl⁻ increase determines the subsequent accumulations. During the second phase, Cl⁻ levels correlated with abscission in leaves. Production of leaf ethylene was also concomitant with the increase in the abscission rate. Salt‐induced abscission was either reduced with CoCl₂ (52%) or inhibited with silver thiosulphate (14%). The results suggest that in salt‐stressed citrus, leaf abscission is induced by the chloride build‐up through a mechanism that stimulates leaf ACC synthesis and further conversion to ethylene.     

Modification of Vegetative Phenology in a Tropical Semi‐deciduous Forest by Abnormal Drought and Rain1

The control of vegetative phenology in tropical trees is not well understood. In dry forest trees, leaf abscission may be enhanced by advanced leaf age, increasing water stress, or declining photoperiod. Normally, it is impossible to dissect the effects of each of these variables because most leaves are shed during the early dry season when day length is near its minimum and leaves are relatively old. The 1997 El‐Niño Southern Oscillation caused a ten‐week long, severe abnormal drought from June to August in the semi‐deciduous forests of Guanacaste, Costa Rica. We monitored the effect of this drought on phenology and water status of trees with young leaves and compared modifications of phenology in trees of different functional types with the pattern observed during the regular dry season. Although deciduous trees at dry sites were severely water stressed (Ψstem < ‐7MPa) and their mesic leaves remained wilted for more than two months, these and all other trees retained all leaves during the abnormal drought. Many trees exchanged leaves three to four months earlier than normal during the wet period after the abnormal drought and shed leaves again during the regular dry season. Irrigation and an exceptional 70 mm rainfall during the mid‐dry season 1998/1999 caused bud break and flushing in all leafless trees except dormant stem succulents. The complex interactions between leaf age and water stress, the principal determinants of leaf abscission, were found to vary widely among trees of different functional types.     

Changes in the accumulation of flavonoid and isoflavonoid conjugates associated with plant age and nodulation in alfalfa (Medicago sativa)

Carbohydrate and mineral nutrition was studied in relation to abscission in fruitlets from leafy inflorescences of the Washington navel orange ( Citrus sinensis [L.] Osbeck). Differences in the growth rate of the fruitlets permitted to predict abscission several weeks in advance. This allowed characterization of early differences in composition and behaviour of persisting and abscising fruitlets.
Inflorescences with persisting fruitlets accumulated more mineral elements than inflorescences with abscising fruitlets, and for the phloem-mobile elements the excess accumulation was allocated to the fruitlets. Starch accumulated in the inflorescence leaves during early fruitlet growth, and this accumulation was enhanced by the persisting fruitlets despite their higher growth rate and mobilizing ability. The relations between the fruitlets and the inflorescence leaves cannot be explained totally in terms of source sink relationships; a hormonal regulation of the leaves by the fruitlets is postulated.
Acid invertase activities and hexose concentration in the pericarp were higher in the abscising fruitlets. The lower early growth rate of these fruitlets is thus not caused by a limitation in carbohydrate supply. It seems more related to carbohydrate utilization, probably hormonally mediated, as demonstrated by the higher dependence on hormone supply for the growth in vitro of the endocarp explants.