Flavonoids from Gutierrezia texana var. texana

Eleven flavonoids, including two new compounds, were isolated from Gutierrezia texana: the structures of the new compounds are 5,7,2′,5′-tetrahydroxy-3,4′-dimethoxyflavone and 5′-acetoxy-5,7,2′-trihydroxy-3,4′-dimethoxyflavone. The nine known compounds are 5,4′,5′-trihydroxy-3,6,7,8-tetramethoxyflavone, 5,7,2′,5′-tetrahydroxy-3,6,4′-trimethoxyflavone, 5,7,3′-trihydroxy-3,4′-dimethoxyflavone, 5,7,3′,4′-tetrahydroxyflavone, 3,5,7,3′,4′- pentahydroxyflavone, 5,7,3′,4′-tetrahydroxy-3-methoxyflavone, 5,6,7,3′,4′,-pentahydroxy-3-methoxyflavone, 5,7,3′,4′-tetrahydroxy-3-methoxyflavone 7-O-glucoside and 3,5,7,3′,4′-pentahydroxyflavanone.     

Experimental investigation of pathogenic stress on phytolith formation in Cucurbita pepo var. texana (wild gourd)

Silica phytoliths that form in plant tissues are useful to archaeologists because of their diagnostic value and longevity in ancient deposits. Palaeoecology, site formation processes, plant domestication, and other topics are routinely addressed using phytolith assemblages, especially when macrobotanical remains are not well preserved. However, little research has been conducted to document the effects of ecological variables on phytolith formation. Here, we investigate the effects of mosaic virus and bacterial wilt disease on diagnostic scalloped phytoliths in the rind of a wild-type Cucurbita pepo var texana (gourd). We observe a minimal change in phytolith size distribution between control plants and individuals with mosaic virus. However, we observe a notable difference between plants with bacterial wilt disease and control plants, with diseased individuals carrying a greater proportion of large-diameter scalloped phytoliths. This and similar phenomena could potentially confound archaeological interpretations of phytolith assemblages, and we suggest that the effects of this and other ecological variables should be studied in a diverse range of taxa.     

Effects of pollen selection on progeny vigor in a Cucurbita pepo x C. texana hybrid

We examined the effects of pollen selection for rapid pollen-tube growth on progeny vigor. First, we crossed a wild gourd (Cucurbita texana) to a cultivated zucchini (Cucurbita pepo cv Black Beauty) to produce an F₁ and then an F₂ generation. Half of the F₁ seeds were produced by depositing small loads of C. texana pollen onto the stigmas of C. pepo. These small pollen loads were insufficient to produce a full complement of seeds and, consequently, both the fast- and the slow-growing pollen tubes were permitted to achieve fertilization. An F₂ generation was then produced by depositing small loads of F₁ pollen onto stigmas of F₁ plants. The F₂ seeds resulting from two generations of small pollen loads are termed the non-selected line because there was little or no selection for pollen-tube growth rate on these plants. The other half of the F₁ and F₂ seeds were produced by depositing large pollen loads (>10 000 pollen grains) onto stigmas and then allowing only the first 1% or so of the pollen tubes that entered the ovary to fertilize the ovules. We did this by excising the styles at the ovary at 12–15 h after pollination. The resulting F₂ seeds are termed the selected line because they were produced by two generations of selection for only the fastest growing pollen tubes. Small pollen loads from the F₂plants, both the selected and the non-selected lines, were then deposited onto stigmas of different C. pepo flowers, and the vigor of the resulting seeds was compared under greenhouse and field conditions. The results showed that the seeds fertilized by pollen from the selected line had greater vegetative vigor as seedlings and greater flower and fruit production as mature plants than the seeds fertilized by pollen from the non-selected line. This study demonstrates that selection for fast pollen-tube growth (selection on the microgametophyte) leads to a correlated increase in sporophyte (progeny) vigor.     

Mavicyanin, a blue copper protein from Cucurbita pepo medullosa. Purification and characterization.

1. The copper protein mavicyanin has been isolated and purified from the green squash Cucurbita pepo medullosa. 2. Mavicyanin contains one type-1 copper/18000 Mr, which can be characterized by: intense absorption maximum at 600 nm (epsilon = 5000 M-1 cm-1/Cu, A280/A600 = 8.0 +/- 0.5, A600/A403 = 7.0 +/- 0.25, maximum of fluorescence emission at 335 nM. 3. In the oxidized state the copper of mavicyanin is 100% detectable by electron paramagnetic resonance (EPR). Computer simulation of the rhombic EPR signal gives gz = 2.287, gy = 2.077, gx = 2.025, Az = 3.5 mT, Ay = 2.9 mT and Ax = 5.7 mT. 4. Like other simple type-1 copper proteins, such as stellacyanin, azurin or plastocyanin, mavicyanin is readily reduced by hydroquinone or L-ascorbic acid. Its midpoint potential E'm was determined to be + 285 mV. The reduced protein reacts rather slowly with dioxygen, but is rapidly reoxidized by ferricyanide.     

Multigenerational effects of inbreeding in Cucurbita pepo ssp. texana (Cucurbitaceae)

The shape of the fitness function relating the decline in fitness with coefficient of inbreeding (f) can provide evidence concerning the genetic basis of inbreeding depression, but few studies have examined inbreeding depression across a range of f using noncultivated species. Futhermore, studies have rarely examined the effects of inbreeding depression in the maternal parent on offspring fitness. To estimate the shape of the fitness function, we examined the relationship between f and fitness across a range off from 0.000 to 0.875 for components of both male and female fitness in Cucurbita pepo ssp. texana. Each measure of female fitness declined with f, including pistillate flower number, fruit number, seed number per fruit, seed mass per fruit, and percentage seed germination. Several aspects of male fitness also declined with f, including staminate flower number, pollen number per flower, and the number of days of flowering, although cumulative inbreeding depression was less severe for male (0.34) than for female function (0.39). Fitness tended to decline linearly with f between f = 0.00 and f = 0.75 for most traits and across cumulative lifetime fitness (mean = 0.66), suggesting that individual genes causing inbreeding depression are additive and the result of many alleles of small effect. However, most traits also showed a small reduction in inbreeding depression between f = 0.75 and f = 0.875, and evidence of purging or diminishing epistasis was found for in vitro pollen-tube growth rate. To examine inbreeding depression as a maternal effect, we performed outcross pollinations on f = 0.0 and f = 0.5 mothers and found that depression due to maternal inbreeding was 0.07, compared to 0.10 for offspring produced through one generation of selfing. In at least some families, maternal inbreeding reduced fruit number, seed number and mass, staminate flower number, pollen diameter, and pollen-tube growth rate. Collectively these results suggest that, while the fitness function appears to be largely linear for most traits, maternal effects may compound the effects of inbreeding depression in multigenerational studies, though this may be partially offset by purging or diminishing epistasis.     

Inbreeding effects on blossom volatiles in Cucurbita pepo subsp. texana (Cucurbitaceae)

Self-pollination by plants gives rise to inbreeding depression. There is increasing recognition that plant inbreeding can have significant implications for interactions between plants and other organisms, including insects and pathogens. Many of these interactions are mediated by plant-derived volatiles, but the effects of inbreeding on volatile production have not previously been investigated. We examined variation in flower volatile production by the wild gourd Cucurbita pepo subsp. texana as a function of inbreeding, sex of the flower, and maternal line. We compared first-generation selfed progeny to outcrossed progeny to assess variation in blossom volatiles due to mating system. Our data indicate that self-pollination reduces total volatile production and changes the relative composition of individual compounds released by C. pepo subsp. texana blossoms. These findings have potentially important implications for interactions between C. pepo subsp. texana and its pollinators and herbivores-including diabroticite cucumber beetles, which vector the bacterial pathogen Erwinia tracheiphila-because previous studies have shown that a number of the individual compounds that vary with inbreeding level can influence insect behavior. We also found significant differences between the volatile profiles of male and female flowers and across maternal families.     

Ascorbate oxidase from Cucurbita pepo medullosa. New method of purification and reinvestigation of properties.

1. Ascorbate oxidase has been isolated from the green squash Cucurbita pepo medullosa by a new purification method. Furthermore a low-molecular-weight copper protein containing one type-1 copper/20000 Mr could be separated during the purification of the oxidase. The six-step procedure developed improved the yield of ascorbate oxidase by a factor of 2.5. The method is well reproducible and a constant value of 8 Cu (7.95 +/- 0.1/140000 Mr) has been established. By ultracentrifugal and electrophoretic criteria the enzyme preparations have been found to be homogeneous. They exhibited a specific activity of 3930 +/- 50 units/mg protein or 1088 +/- 15 units/microgram copper. 2. The pure enzyme is characterized by the following optical purity indices: A280/A610 = 25 +/- 0.5, A330/A610 = 0.65 +/- 0.05 and A610/A500 = 7.0 +/- 0.25. The molar absorption coeffient of the characteristic absorption maximum at 610 nm (oxidized minus reduced) amounts of 9700 M-1 cm-1 . 3. Computer simulations of the electron paramagnetic resonance (EPR) spectra of the oxidized enzyme reveal the following parameters: for the type-1 (blue) copper gz = 2.227, gy = 2.058, gx = 2.036; Az = 5.0 mT, Ay = Ax = 0.5 mT, for the type-2 (non-blue) copper g parallel to = 2.242, g perpendicular = 2.053; A parallel to = 19.0 mT, A perpendicular 0.5 mT. Out of the eight copper atoms present in the oxidase four are detectable by EPR. Of these, three belong to the type-1 class, and one to the type-2 class, as demonstrated by computer simulations of the EPR spectra. 4. To achieve full reduction of the enzyme, as measured by bleaching of the blue chromophore, four equivalents of L-ascorbate or reductase must be added in the absence of molecular oxygen. Upon reduction of the enzyme the fluorescence at 330 nm (lambda max ex = 295 nm) is enhanced by a factor of 1.5 to 1.75. The reduced enzyme is readily reoxidized by dioxygen, ferricyanide or hydrogen peroxide. It binds two molecules of hydrogen peroxide in the oxidized state (1/type-3 Cu pair), which can be monitored by a characteristic increase of the absorbance around 310 nm (delta epsilon = 1000 +/- 50 M-1 cm-1). Corresponding changes in EPR and fluorescence spectra have not been detected.     

Allozyme variation in endangered Castanea pumila var. pumila

Allozyme genetic variation in 12 populations of the endangered Castanea pumila var. pumila (Allegheny chinkapin), sampled across the natural range of the species in the United States, was evaluated using 11 loci from seven enzyme systems. At the species level, the percentage of polymorphic loci (Ps) was 72.7 %, the mean number of alleles per locus (As) was 1.9, the mean number of alleles per polymorphic locus (APs) was 2.3, the effective number of alleles per locus (Aes) was 1.5 and the genetic diversity (Hes) was 0.296. At the population level, Pp = 49.2 %, Ap = 1.5, Aep = 1.4, APp = 2.1 and Hep = 0.21. Most of the allozyme variation (70 %) in C. pumila var. pumila occurred within populations. Wright's gene flow rate [Nm(W)] was as low as 0.57. Population differentiation along the species range was not detected. Populations of C. pumila var. pumila in Florida had the most variable levels of genetic diversity, but populations in Virginia and Mississippi also showed high levels. Based on the results of this study, conservation management strategies are discussed.     

Environmental variation influences the magnitude of inbreeding depression in Cucurbita pepo ssp. texana (Cucurbitaceae)

We grew inbred and outcrossed Cucurbita pepo ssp. texana plants and measured inbreeding depression for several male and female fitness traits 4 years in a row in adjacent fields at the same field station under the same cultivation conditions. We found that the magnitude of inbreeding depression varied from 0.16 to 0.53 from year to year and that those traits which were most affected tended to vary with year. We also grew inbred and outcrossed C. pepo ssp. texana plants in two adjacent fields differing only in the presence of nitrogen fertilizer to examine the effect of nutrient limitation as a form of environmental stress on the magnitude of inbreeding depression. We found that inbreeding depression was more severe in the unfertilized field. Overall, this study illustrates the notion that any estimate of inbreeding depression represents a single point in a cluster of possible estimates that can vary (often dramatically) with growing conditions.     

A comparison of male and female responses to inbreeding in Cucurbita pepo subsp. texana (Cucurbitaceae)

Accurate estimates of inbreeding depression are necessary in order to predict the evolutionary dynamics of a population, but many studies estimate inbreeding depression based solely on components of female function such as fruit set, seed set, and seed quality. Because total fitness is achieved through both male and female functions in hermaphroditic plants, estimates of both male and female fitness are needed to estimate accurately the magnitude of inbreeding depression. Seedlings of a wild gourd, Cucurbita pepo subsp. texana, with coefficients of inbreeding of 0 and 0.75 were planted in an experimental garden, and several components of male and female fitness were measured over the course of the growing season. Fitness in inbred plants was confounded by both maternal and genetic inbreeding effects. Inbred individuals produced significantly fewer fruits than outcrossed individuals, and percentage germination of seeds from inbred individuals was significantly lower than seeds from outcrossed individuals. Inbred plants also produced significantly fewer staminate flowers and marginally fewer and smaller pollen grains per flower. Pollen from inbred plants also grew significantly more slowly in vitro than pollen from outcrossed plants. Multiplicative estimates of inbreeding depression revealed inbreeding depression for both male and female functions in wild gourd, but inbreeding depression through female function was stronger than inbreeding depression through male function.     

Genetic differentiation between Coffea liberica var. liberica and C. liberica var. Dewevrei and comparison with C. canephora

Coffea liberica Hiern includes C. liberica var. liberica (LIB) from western Africa and C. liberica var. dewevrei (DEW) from central Africa. This geographical distribution also includes cultivated C. canephora for which a within-species clustering in two interfertile groups is known. In this study, genetic differentiation between LIB and DEW was evaluated on the basis of morphological traits, molecular markers (AFLP) and male fertility of F1 hybrids. The results were also compared with the within-species differentiation in C. canephora. The morphological traits differed significantly but the distributions overlapped. By contrast, LIB and DEW constituted two distinct groups with high genetic differentiation (G_st=0.25) when using AFLP markers. In addition, the pollen viability of F1 hybrids between LIB and DEW was weak (44.2%) and similar to interspecific C. canephora x DEW F1 hybrids or C. canephora x LIB F1 hybrids, indicating that there are marked reproductive barriers between LIB and DEW.     

Leaf herbivory increases floral fragrance in male but not female Cucurbita pepo subsp. texana (Cucurbitaceae) flowers

Mutualisms are key interactions that affect population dynamics and structure communities, but the extent to which mutualists can attract potential partners may depend on community context. Many studies have shown that leaf herbivory reduces pollinator visitation and have focused on reduced floral visual display and rewards as potential mechanisms. However, olfactory display plays a critical role in mediating interactions between plants, herbivores, and pollinators. We simulated leaf damage in Cucurbita pepo subsp. texana and measured fragrance emission and other floral characters of both male and female flowers. Contrary to our expectations, damage increased fragrance production, but only in male flowers. Female flowers, which were bigger and produced more fragrance than males, were unaffected by leaf damage. The greatest increase in floral fragrance compounds was in the terpenoids, which we hypothesize could be byproducts of defensively induced cucurbitacins, or they may function defensively themselves. In summary, this study is the first to demonstrate changes in floral fragrance due to leaf damage. Such changes in floral fragrance following herbivory may be a critical and overlooked mechanism mediating interactions between plants, herbivores, and pollinators.     

Allozyme differentiation of bonito in the Mediterranean Sea

Bonito Sarda sarda samples collected in three areas from the Mediterranean Sea exhibited considerable genetic heterogeneity over all locations. This provided preliminary evidence for two different groups of bonito, one for the Ligurian and the Ionian Seas and the other for the Aegean Sea.     

光叶珙桐的等位酶分析及其生物地理学意义

采用水平切片淀粉凝胶电泳实验方法,对光叶珙桐(Davidia involucrata var．vilmoriniana)4个居群、78个个体、11种酶系统,21个位点进行了等位酶分析。各居群的多态位点百分比P＝28.6％-47．6％,实际杂合度Ho＝0．177—0.308,平均每个位点的等位基因数A=1．3-1．6。在变种水平上,多态位点百分比P＝52．4％,平均每个位点的等位基因数A＝1．8,实际杂合度Ho＝0．272,期望杂合度Ho＝0．216。基因分化系数FST＝0．1928,说明光叶珙桐居群问分化小。各项指标表明光叶珙桐的遗传多样性水平较高,比原变种珙桐高,外部环境可能是影响珙桐分布格局的重要因素。昭通与宝兴的遗传多样性明显高于其他两个居群,遗传多样性保存较为完整,而处于分布区东、西两侧边缘(云南西北部和湖北五峰)遗传多样性则相对较低,推测四川盆地边缘山地是该种的遗传多样化中心,可能是在地质灾难中(如第四纪冰期),光叶珙桐真正的避难所。分布区东西两侧的居群可能是从四川盆地边缘山地扩散而来。     

金瓜和白瓜花叶病毒病病原的初步鉴定

崇明是上海出口蔬菜生产基地之一,也是国家级的绿色食品园区之一,具有生产绿色蔬菜商品的生态环境和资源优势.     

金瓜和白瓜花叶病毒病病原的初步鉴定

崇明是上海出口蔬菜生产基地之一,也是国家级的绿色食品园区之一,具有生产绿色蔬菜商品的生态环境和资源优势。特色出口蔬菜金瓜(Cucurbita pepo L.var.ovifera)、白瓜(Cucumis melo L.var.conomon,又名盐渍菜瓜)1997～1999统计病毒病发病率为23％,被感染的金瓜、白瓜田     

Allozyme variation and differentiation in African and Indian rhinoceroses

We studied variation at 25 to 31 allozymic loci in African and Asian rhinoceroses. Four taxa in three genera were examined: African Ceratotherium simum simum (northern white rhinoceros), C. s. cottoni (southern white rhinoceros), Diceros bicornis (black rhinoceros), and Rhinoceros unicornis (Indian rhinoceros). Extremely small amounts of intraspecific variation were observed in sample sizes of 2 to 10 presumably unrelated individuals per taxon: P = .00-.10, H = 0.00-0.02. We examined demographic bottlenecks and sampling errors as possible reasons for the low levels of detectable variation. The very small intraspecific genetic distance (D = 0.005) between the two living white rhinoceros subspecies is far less than the distance that has been reported for other mammal subspecies. The mean D value of 0.32 +/- 0.11 between the two African genera was also less than expected given the divergence time of greater than 7 million years suggested by the fossil record. Rhinoceroses may be evolving more slowly at the structural gene loci than are some other mammal groups. The estimate of D = 1.05 +/- 0.24 for the African-Indian split supports this idea, as the lineage diverged at least 26 million years ago. Our results contribute to the currently available scientific information on which management decisions aimed toward saving endangered rhinoceroses should be based.     

Geographic isolation and climatic heterogeneity drive population differentiation of Rosa chinensis var. spontanea complex

• Global biodiversity is contracting rapidly due to potent anthropogenic activities and severe climate change. Wild populations of Rosa chinensis var. spontanea and Rosa lucidissima are rare species endemic to China, as well as important germplasm resources for rose breeding. However, these populations are at acute risk of extinction and require urgent action to ensure their preservation.
• We harnessed 16 microsatellite loci to 44 populations of these species and analysed population structure and differentiation, demographic history, gene flow and barrier effect. In addition, a niche overlap test and potential distribution modelling in different time periods were also carried out.
• The data indicate that: (1) R. lucidissima cannot be regarded as a separate species from R. chinensis var. spontanea; (2) the Yangtze River and the Wujiang River function as barriers in population structure and differentiation, and precipitation in the coldest quarter may be the key factor for niche divergence of R. chinensis var. spontanea complex; (3) historical gene flow showed a converse tendency to current gene flow, indicating that alternate migration events of R. chinensis var. spontanea complex between south and north were a response to climate oscillations; and (4) extreme climate change will decrease the distribution range of R. chinensis var. spontanea complex, whereas the opposite will occur under a moderate scenario for the future.
• Our results resolve the relationship between R. chinensis var. spontanea and R. lucidissima, highlight the pivotal roles of geographic isolation and climate heterogeneity in their population differentiation, and provide an important reference for comparable conservation studies on other endangered species.

     

Effect of tunicamycin on the activity and immunoreactivity of ascorbate oxidase (Cucurbita pepo medullosa) expressed in cultured green zucchini cells

Ascorbate oxidase activity and immunoreactivity were evaluated in crude tissue extracts obtained from callus cell cultures induced by green zucchini sarcocarp and grown in the presence of tunicamycin, a powerful N-glycosylation inhibitor. Tunicamycin at 2 or 4 g ml–1 blocked cell growth within a couple of weeks, although a sustained cell viability was observed in the same period. A significant inhibition of total protein synthesis was observed at 10 and 15 days of culture time, with a decrease of 30% and 43% respectively when cells were grown in the presence of 2 g ml–1 tunicamycin, and of 48% and 57% respectively when the tunicamycin concentration was 4 g ml–1. After the same culture times ascorbate oxidase specific activity assayed in crude tissue extracts showed increases of about 1.9-fold and 3.5-fold (10 days) and 1.7-fold and 3.1-fold (15 days) at 2 and 4 g ml–1 tunicamycin, respectively. Ascorbate oxidase mRNA levels, however, did not appreciably differ between control and treated samples, measured at the same growing times. Lectin-blot, based on the use of concanavalin A, indicated a marked decrease of glycosylated proteins in tunicamycin-treated cultures. As judged by immunoblot, anti-native ascorbate oxidase antibodies scarcely recognized the enzyme expressed in tunicamycin-treated cells; on the contrary, anti-deglycosylated ascorbate oxidase antibodies were more reactive to the enzyme expressed in tunicamycin-treated cultures.     

Purification and characterization of the trypsin inhibitor from Cucurbita pepo var. patissonina fruits

Three trypsin inhibitor fractions were found in white bush fruits (Cucurbita pepo L. var. patissonina). One of them, CPPTI-fIII, was purified to homogeneity by means of affinity and ion exchange chromatography. It is a cysteine-poor protein with an approximate Mr of 21 000. The inhibitor contains arginine at position P1 of the reactive site and inhibits bovine trypsin, hog pancreatic kallikrein and subtilisin. This inhibitor differs from the inhibitors of white bush dormant seeds, CPPTI-I and CPPTI-II, in its amino-acid composition, molecular mass, amino-acid residue at position P1 of the reactive site and inhibition spectrum.