Interspecific pollen transfer between two coflowering species was minimized by bumblebee fidelity and differential pollen placement on the bumblebee body

Aims When sympatric flowering plant species in a natural community share pollinators,study of plant-plant interactions via interspecific pollen transfer(iPT)is essential for understanding species coexistence.However,little is known about the extent of iPT between interactive species and its causes.Methods To explore how sympatric flowering plants sharing pollinators mini-mize deleterious effects of iPT,we investigated the pollination ecol-ogy of two endemic species,Salvia przewalskii and Delphinium yuanum,in an alpine meadow in the Hengduan mountains,southwest China.We quantified conspecific and interspecific visits by shared bumblebee pollinators,amounts of pollen placed on different body sites of the pollinators and stigmatic pollen loads on open-pollinated flowers.To examine whether iPT affects female fitness,we measured pollen germination and seed production in the two species in an artificial pollination experiment.Important Findingsone bumblebee species,Bombus trifasciatus,was found to be the sole effective pollinator for the two coflowering species.Pollination experiments indicated that deposition of heterospecific pollen could significantly decrease seed set in both species.Experiments showed that S.przewalskii pollen could germinate well on stigmas of D.yuanum,inhibiting conspecific pollen germination in D.yuanum.However,seed set was not lower under open pollination than under cross-pollination within species,suggesting that no female fitness loss was caused by iPT.in foraging bouts with pollinator switches,switches from S.przewalskii to D.yuanum were relatively more fre-quent(8.27%)than the converse(1.72%).However,iPT from S.prze-walskii to D.yuanum accounted for only 1.82%of total stigmatic pollen loads while the reverse iPT to S.przewalskii was 8.70%,indi-cating that more switches of bumblebees to D.yuanum did not result in higher iPT.by contrast,selection for reduced iPT to S.przewalskii would limit pollinator switches from D.yuanum.We found that a bumblebee generally carried pollen grains from both species but the two species differed in the position of pollen placement on the bum-blebee’s body;S.przewalskii’s pollen was concentrated on the dorsal thorax while D.yuanum’s pollen was concentrated ventrally on the head.This differential pollen placement along with pollinator fidelity largely reduced iPT between the two species with a shared pollinator.

Enhancement of innate immune system in monocot rice by transferring the dicotyledonous elongation factor Tu receptor EFR

The elongation factor Tu （EF-Tu） receptor （EFR） in cruciferous plants specifically recognizes the N-terminal acetylated elf18 region of bacterial EF-Tu and thereby activates plant immunity. It has been demonstrated that Arabidopsis EFR confers broad-spectrum bacterial resistance in the EFR transgenic solanaceous plants. Here, the transgenic rice plants （Oryza sativa L. ssp. japonica cv. Zhonghua 17） and cell cultures with constitutive expression of AtEFR were developed to investigate whether AtEFR senses EF-Tu and thus enhances bacterial resistance in the monocot plants. We＇demonstrated that the Xanthomonas oryzae-derived elf18 peptide induced oxidative burst and mitogen-activated protein kinase activa- tion in the AtEFR transgenic rice cells and plants, respectively. Pathogenesis-related genes, such as OsPBZ1, were upregulated dramatically in transgenic rice plant and cell lines in response to elf18 stimulation. Importantly, pretreatment with elf18 trig- gered strong resistance to X. oryzae pv. oryzae in the transgenic plants, which was largely dependent on the AtEFR expressionlevel. These plants also exhibited enhanced resistance to rice bacterial brown stripe, but not to rice fungal blast. Collectively, the results indicate that the rice plants with heterologous expression of AtEFR recognize bacterial EF-Tu and exhibit enhanced broad-spectrum bacterial disease resistance and that pattern recognition receptor-mediated immunity may be manipulated across the two plant classes, dicots and monocots.

In vivo and in vitro development of Tibetan antelope(Pantholops hodgsonii)interspecific cloned embryos

The Tibetan antelope is endemic to the Tibetan Plateau,China,and is now considered an endangered species.As a possible rescue strategy,the development of embryos constructed by interspecies somatic cell nuclear transfer(iSCNT)was examined.Tibetan antelope fibroblast cells were transferred into enucleated bovine,ovine and caprine oocytes.These cloned embryos were then cultured in vitro or in the oviducts of intermediate animals.Less than 0.5%of the reconstructed antelope-bovine embryos cultured in vitro developed to the blastocyst stage.However,when the cloned antelope-bovine embryos were transferred to caprine oviducts,about 1.6%of the embryos developed to the blastocyst stage.In contrast,only 0.7%of the antelope-ovine embryos developed to the morula stage and none developed to blastocysts in ovine oviducts.The treatment of donor cells and bovine oocytes with trichostatin A did not improve the embryo development even when cultured in the oviducts of ovine and caprine.When the antelope-bovine embryos,constructed from oocytes treated with roscovitine or trichostatin A,were cultured in rabbit oviducts 2.3%and 14.3%developed to blastocysts,respectively.It is concluded that although some success was achieved with the protocols used,interspecies cloning of Tibetan antelope presents difficulties still to be overcome.The mechanisms resulting in the low embryo development need investigation and progress might require a deeper understanding of cellular reprogramming.