Evidence of selection for egg crypsis in conspicuous nests

ABSTRACT The value of egg coloration as crypsis, once accepted as a general principle, has recently been questioned because most experiments have failed to show that egg coloration deters predation. The nest‐crypsis hypothesis postulates that, among species that build conspicuous nests, selection for egg crypsis is relaxed or absent because visually searching predators detect nests prior to eggs. I tested the nest‐crypsis hypothesis using the large, relatively conspicuous nests of American Robins (Turdus migratorius), and eggs that differed markedly in color that were collected from the nests of Red‐winged Blackbirds (Agelaius phoeniceus), Brewer's Blackbirds (Euphagus cyanocephalus), and Yellow‐headed Blackbirds (Xanthocephalus xanthocephalus). Each nest (N= 22) received a clutch of each species during three sequential predation trials that were 16 d in duration. The order of clutch presentation was randomized for each nest. Survival trends for Brewer's and Yellow‐headed Blackbirds were similar, and higher than those for clutches of Red‐winged Blackbirds. By the end of trials, overall survival of the three clutch types was roughly equivalent. However, clutches of Red‐winged Blackbird eggs, the most conspicuous egg type to the human eye, were discovered sooner by predators. Because the experimental design controlled for effects of nest crypsis, nest location, and nest size, this difference in egg survival can be attributed to differences in egg pigmentation. Thus, my results support a role for egg coloration as camouflage in conspicuous nests.     

Elicitation of Ethylene by Verticillium albo-atrum Phytotoxins in Potato

Petioles from a susceptible cultivar (Désirèe) of Solanum tuberosum treated with a low‐molecular mass toxin, separated from culture fluid of Verticillium albo‐atrum, produced greater quantities of ethylene than did petioles of a tolerant cultivar (Home Guard). Pretreatment of leaflets from cv. Désirèe with silver thiosulphite, which inhibits perception of ethylene, prevented the chlorosis and necrosis normally associated with exposure to the toxin. Similarly, application of aminoethoxyvinylglycine (AVG) an inhibitor of aminocyclopropane‐1‐carboxylic acid (ACC) synthase, to petioles of cv. Désirèe reduced toxin‐induced ethylene synthesis and symptom development. The data indicate that, in part, Verticillium‐toxin acts through induction of ethylene biosynthesis in the host tissues, and different responses of susceptible and tolerant potato cultivars to V. albo‐atrum are the result of differential production of ethylene.     

Response of Globodera rostochiensis to exogenously applied hatching factors in soil

The exogenous application of hatching factors (HFs) to soil in the field gave an approximately 50% reduction in the population size of Globodera rostochiensis. This control was found to be due to a combination of suicide hatch and increased in‐egg mortality caused presumably by incomplete hatch stimulation. The rates of hatch and emergence of J2s from cysts of G. rostochiensis were found to be dependent on hatching factor concentration in vitro and in the field. Encysted eggs of G. rostochiensis in the field during the first year of rotation after the previous year's potato crop were found to be more sensitive to HF concentration than those in the second year of rotation.     

Development of a molecular marker associated with Verticillium wilt resistance in diploid interspecific potato hybrids

Verticillium wilt (VW) is a widespread and serious potato (Solanum tuberosum) disease caused by the soilborne fungi Verticillium dahliae and V. albo-atrum. Breeding for VW resistance in potato is challenging due to ambiguous symptom expression, a lack of high throughput screening techniques, and variability in colonization by the fungus among and within plants. Genetic studies have identified major genes that confer resistance in diploid Solanum chacoense (V _c ) and interspecific hybrids (V _w and V _t ). However, to date, these genes have not been used to develop molecular markers for the identification of resistant clones. Tomato Ve1 and Ve2 gene sequence information was used to amplify candidate Ve gene orthologs from both resistant and susceptible diploid potato hybrids. A CAPS marker was generated to track VW resistance in a backcross population segregating for resistance. The marker was also tested for its usefulness in other breeding lines. Our results indicate that this marker is effective for selection of the V _w gene in segregating breeding populations.     

A convenient system for highly specific and sensitive detection of miRNA expression

Since the first miRNA was discovered in 1993, miRNAs have become a hotspot for biological research. In order to feed this demand, a robust method is required to detect miRNA gene expression. Development of a detection method is more difficult for miRNAs than for long RNAs, such as mRNA, owing to their small size. Existing methods have limitations; thus, new methods are required. We describe a new system for detecting miRNA expression, which can distinguish miRNA from its precursor and has single-nucleotide resolution. It has single molecule and multiplex detection potential. It may be performed as a polymerase chain reaction (PCR) method, a blotting method, or a macroarray method according to the analyst''s preference. This personalized system provides a convenient tool for the detection of miRNA gene expression.     

Pollination success in monochromic yellow populations of the rewardless orchid Dactylorhiza sambucina

Dactylorhiza sambucina is a European terrestrial orchid that lacks a pollinator reward. Throughout most of its range, populations contain yellow- and purple-flowering individuals, but in western Germany, monomorphic yellow populations predominate. As elsewhere, bumblebee queens are the most important pollinators in these populations, and mean fruit set over two years was 19%, well within the range reported from dimorphic populations. Multivariate analyses of plant and population traits, including plant height, leaf number, flower number and density on the spikes, flowering population density, and nearest neighbor distance, showed that only individual plant height and population density had a unique positive effect on pollen export; female function was unrelated to height or population density. The positive effects of dense spacing of flowering conspecifics and tall size appear due to greater visual attractiveness. Good visual exposure may also explain that flowers higher up on the spikes, in spite of opening late in the season, had higher male reproductive success than early flowers.     

基质供水状况对甜椒穴盘苗C、N代谢产物的影响及其与发育的关系

在基质供水状况分别为90％、75％、60％、45％、30％RWC供水下限处理条件下,对甜椒穴盘苗碳氮代谢产物的变化及其与发育的关系进行了探讨。结果表明：随着供水下限的降低,作为渗透调节物质和C代谢原料的可溶性糖迅速积累,这有利于提高逆境下幼苗的适应性。蔗糖与可溶性糖积累同步,是可溶性糖的主要成分。淀粉与总碳水化合物变化趋势基本一致,其变化趋势在一定程度上反映了碳水化合物的积累状况。供水状况对总N影响不太大,但显著改变蛋白氮和非蛋白氮的比例。非蛋白氮和游离氨基酸含量随供水下限降低显著上升,而蛋白氮却显著下降。水分变化主要通过改变N的源库关系,导致生长发育延迟。硝酸还原酶活性的升高并没有弥补缺水而致N素吸收的降低。C、N代谢问存在互为消长的关系,75％供水下限处理的甜椒C／N比最高,开花最早。综合生长发育及碳、氮代谢,认为75％基质相对含水量为甜椒穴盘苗适宜的供水下限。     

CDOM transport from the Bahamas Banks

The transport of colored dissolved organic matter (CDOM) between shallow banks and deep basins in the Bahamas was the focus of this study. Hydrographic and CDOM absorption measurements made on the Bahamas Banks and in Exuma Sound during the spring of 1999 and 2000 showed that values of salinity and CDOM absorption at 440 nm were higher on the banks (37.18 psu, 0.06 m^–1), compared to Exuma Sound (37.04 psu, 0.03 m^–1). Spatial patterns of CDOM absorption in Exuma Sound revealed that plumes of CDOM-rich water flow into Exuma Sound from the surrounding banks. These patterns were determined using Sea-viewing Wide Field-of-view Sensor (SeaWiFS) data processed using a Moderate Resolution Imaging Spectroradiometer (MODIS) algorithm to derive CDOM absorption estimates. These data, along with time-series data collected in a channel between the banks and sound, suggest that bank water rich in CDOM and salinity leaves the banks during ebb tide, whereas sound water, with lower levels of CDOM and salinity, extends onto the banks during flood tide. Because CDOM absorbs ultraviolet radiation, a causal factor of reef organism bleaching, we discuss the meaning of our findings in terms of susceptibility to coral bleaching in the Exuma region.     

The "resurrection method" for modification of specific proteins in higher plants

We describe a new method designated "the resurrection method" by which a modified protein is expressed in higher plants in place of the original protein. The modified gene constructed by introducing synonymous codon substitutions throughout the original gene to prevent the sequence-specific degradation of its mRNA during RNA silencing is expressed while the expression of the original gene is suppressed. Here, we report the successful alteration of the biochemical properties of green fluorescent protein expressed in transgenic Nicotiana benthamiana, suggesting that this method could be useful for gene control in living plants.     

BmStart1, a novel carotenoid-binding protein isoform from Bombyx mori, is orthologous to MLN64, a mammalian cholesterol transporter

Carotenoid-binding protein (CBP) from the silkworm Bombyx mori is an essential molecule for carotenoid dependent cocoon pigmentation. We identified a novel isoform of CBP, Start1 of B. mori (BmStart1). BmStart1 contains a membrane-spanning MENTAL domain in its N-terminus and a lipid-binding START domain in its C-terminus. This domain architecture is identical to the mammalian MLN64 and Start1 of Drosophila melanogaster (DmStart1), both of which have been implicated to function in cholesterol transport and regulation of steroidogenesis. BmStart1 is expressed in both white and yellow cocoon strains of B. mori, while CBP is only detected in the yellow cocoon strain. BmStart1 mRNA abundance in the prothoracic gland, the main ecdysteroidogenic tissue, positively correlates with changes in the hemolymph ecdysteroid level. Genomic sequence analysis revealed that BmStart1 and CBP are generated from the same gene locus by alternative splicing. Splice site comparison and homology search indicate that BmStart1 is orthologous to both MLN64 and DmStart1. This study implies that alternative splicing of the BmStart1/CBP gene generates unique protein isoforms whose endogenous ligands, sterol or carotenoid, are structurally different.