High toxin concentration in pollen may deter collection by bees in butterfly-pollinated Rhododendron molle.

BACKGROUNDS AND AIMS: The hypothesis that plants evolve features that protect accessible pollen from consumption by flower visitors remains poorly understood. METHODS: To explore potential chemical defenses against pollen consumption, we examined the pollinator assemblage, foraging behaviour, visitation frequency and pollen transfer efficiency in Rhododendron molle, a highly toxic shrub containing Rhodojaponin III. Nutrient (protein and lipid) and toxic components in pollen and other tissues were measured. KEY RESULTS: Overall in the five populations, floral visits by butterflies and bumblebees were relatively more frequent than visits by honeybees. All foraged for nectar but not pollen. Butterflies did not differ from bumblebees in the amount of pollen removed per visit, but deposited more pollen per visit. Pollination experiments indicated that R. molle was self-compatible, but both fruit and seed production were pollen limited. Our analysis indicated that the pollen was not protein-poor and had a higher concentration of the toxic compound Rhodojaponin III than petals and leaves, which compound was undetectable in nectar. CONCLUSION: Pollen toxicity in Rhododendron flowers may discourage pollen robbers (bees) from taking the freely accessible pollen grains, while the toxin-free nectar rewards effective pollinators, promoting pollen transfer. This preliminary study supports the hypothesis that chemical defense in pollen would be likely to evolve in species without physical protection from pollinivores.

[Simulation of PM2.5 Concentration Based on Optimized Indexes of 2D/3D Urban Form].

It is well known that urban forms can affect the source distribution and diffusion process of air pollution; however, practical quantitative methods and models on alleviating urban air pollution by optimizing urban form indexes are lacking. Using Chang Sha city as an example, we quantitatively analyzed the PM2.5 concentration distribution in terms of 2D/3D urban form indexes (e.g., land use functionality, landscape pattern, and development intensity). Based on this, the urban form regulation-aided air quality optimization model (UFR-AQOM) was proposed and consequently employed to simulate the scene-dependent PM2.5 concentrations under double constraints from both the index threshold and air quality objectives. The results showed that the high value area of PM2.5 concentration in Chang Sha featured a "one axis and four nodes" spatial pattern. PM2.5 concentrations in grids with commercial or road land applications, high patch density or high Shannon index, and high land plot ratio or low sky openness were shown to be relatively higher. The development intensity indexes had the greatest impact on the spatial variation in PM2.5 concentration, followed by landscape pattern and land use functionality, and the interaction of factor indexes could significantly strengthen their own single contributions. The UFR-AQOM model, taking into account the contribution differences and interactions among different factors, could effectively simulate the spatial variation in PM2.5 concentration in urban areas (R2=0.65,RMSE=1.40 µg·m-3). In order to meet the regulations of PM2.5 standards, the overall management of landscape pattern indexes, such as the integral dimension of the perimeter surface and patch density, should be strengthened in the main urban area of Changsha. Further, the zoned optimization of PM2.5 concentrations could be implemented by controlling the urban land use indexes, such as the industrial land use ratio and water area ratio, as well as the development intensity indexes such as the land use area ratio. These research results provided support for decisions in the optimization of national territory spatial planning indexes targeting air quality improvement.

Mitochondrial genome of Babesia orientalis, apicomplexan parasite of water buffalo (Bubalus babalis, Linnaeus, 1758) endemic in China.

BACKGROUND: Apicomplexan parasites of the genus Babesia, Theileria and Plasmodium are very closely related organisms. Interestingly, their mitochondrial (mt) genomes are highly divergent. Among Babesia, Babesia orientalis is a new species recently identified and specifically epidemic to the southern part of China, causing severe disease to water buffalo. However, no information on the mt genome of B. orientalis was available. METHODS: Four pairs of primers were designed based on the full genome sequence of B. orientalis (unpublished data) and by aligning reported mt genomes of B. bovis, B. bigemina, and T. parva. The entire mt genome was amplified by four sets of PCR. The obtained mt genome was annotated by aligning with published apicomplexan mt genomes and Artemis software v11. Phylogenetic analysis was performed by using cox1 and cob amino acid sequences. RESULTS: The complete mt genome of B. orientalis (Wuhan strain) was sequenced and characterized. The entire mt genome is 5996 bp in length with a linear form, containing three protein-coding genes including cytochrome c oxidase I (cox1), cytochrome b (cob) and cytochrome c oxidase III (cox3) and six rRNA large subunit gene fragments. The gene arrangement in B. orientalis mt genome is similar to those of B. bovis, B. gibsoni and Theileria parva, but different from those of T. orientalis, T. equi and Plasmodium falciparum. Comparative analysis indicated that cox1 and cob genes were more conserved than cox3. Phylogenetic analysis based on amino acid sequences of cox1, cob and cox1 + cob, respectively, revealed that B. orientalis fell into Babesia clade with the closest relationship to B. bovis. CONCLUSIONS: The availability of the entire mt genome sequences of B. orientalis provides valuable information for future phylogenetic, population genetics and molecular epidemiological studies of apicomplexan parasites.

Occurrence of Theileria and Babesia species in water buffalo (Bubalus babalis, Linnaeus, 1758) in the Hubei province, South China.

The presence and prevalence of tick-borne haemoparasites in water buffalo from the Hubei province, south China was investigated using the reverse line blot (RLB) hybridization assay and phylogenetic analysis of the parasite 18S rRNA gene. Theileria buffeli (19.1%) was the most frequently found species in all of the locations, followed by Babesia orientalis (8.9%), Babesia bovis (1.0%) and Babesia bigemina (0.7%). Only 12 (3.9%) of the samples had mixed infections. Eleven samples with single infections were selected for further characterization using 18S rRNA gene sequence analysis. Phylogenetic analysis showed that the eight T. buffeli 18S rRNA gene sequences obtained grouped into four clusters, of which three grouped with the known T. buffeli types B and D. The remaining five grouped separately from the previously describe T. buffeli types, constituting new T. buffeli types. The two B. bigemina 18S rRNA gene sequences obtained grouped closely with B. bigemina Kunming; this serves as the first report of B. bigemina in the Hubei province. The B. orientalis Daye 18S rRNA gene sequence obtained grouped closely with the previously reported B. orientalis Wuhan strain and with Babesia sp. Kashi 1 and Kashi 2.

Development and evaluation of real-time PCR assay for the detection of Babesia orientalis in water buffalo (Bubalus bubalis, Linnaeus, 1758).

Babesia orientalis is the causative agent of babesiosis in water buffalo (Bubalus babalis, Linnaeus, 1758). In this study, a TaqMan real-time PCR assay was developed for quantitative detection of B. orientalis in water buffalo. Hybridization probe and oligonucleotide primers were designed based on the v4 region of 18S rRNA gene. Detection limit was determined at 2 parasites. Blood samples were collected from experimentally infected water buffalo, as well as from 180 field samples, which were collected from 4 different geographical locations to the north and south of the Yangtse River. The parasite was detected by real-time PCR on day 2 until day 39 post-infection, while reverse line blot (RLB) was on day 6 until day 36 in experimentally infected water buffalo. For the results of 180 field samples, statistical analysis showed no significant difference in relative effectiveness of real-time PCR and RLB. The analysis also indicated that there was no difference in the prevalence of B. orientalis between the regions of south and north of the Yangtse River by both the real-time PCR assay and RLB detection. These results indicated that the parasite infection has spread to the north of the Yangtse River.