Dynamin, a 100-kD GTPase first found in animal cells, is essential for vesicle formation in receptor-mediated endocytosis, synaptic vesicle recycling, and possibly vesicle trafficking in and out of the Golgi apparatus...Dynamin, a 100-kD GTPase first found in animal cells, is essential for vesicle formation in receptor-mediated endocytosis, synaptic vesicle recycling, and possibly vesicle trafficking in and out of the Golgi apparatus. Recently, dynamin-like proteins were also found in some plant cells. We demonstrate here the presence of dynamin with molecular weight of 100 kD in day-lily ( Hemerocallis fulva) pollen based on molecular estimation and Western blotting. The highly purified pollen Dynamin had GTPase activity, which could be stimulated 1.64 fold by calf brain microtubules in vitro. The results from electron microscopic examination showed that the pollen dynamin readily self-assembled into ring-like structures.展开更多
Habitat fragmentation is a major threat for beneficial organisms and the ecosys- tem services they provide. Multiple-habitat users such as wild bees depend on both nesting and foraging habitat. Thus, they may be affec...Habitat fragmentation is a major threat for beneficial organisms and the ecosys- tem services they provide. Multiple-habitat users such as wild bees depend on both nesting and foraging habitat. Thus, they may be affected by the fragmentation of at least two habitat types. We investigated the effects of landscape-scale amount of and patch isolation from both nesting habitat （woody plants） and foraging habitat （specific pollen sources） on the abundance and diet of Osmia bicornis L. Trap-nests of O. bicornis were studied in 30 agricultural landscapes of the Swiss Plateau. Nesting and foraging habitats were mapped in a radius of 500 m around the sites. Pollen composition of larval diet changed as isolation to the main pollen source, Ranunculus, increased, suggesting that （9. bicornis adapted its foraging strategy in function of the nest proximity to main pollen sources. Abundance of O. bicornis was neither related to isolation or amount of nesting habitat nor to isolation or abundance of food plants. Surprisingly, nests ofO. bicornis contained fewer larvae in sites at forest edge compared to isolated sites, possibly due to higher parasitism risk. This study indicates that O. bicornis can nest in a variety of situations by compensating scarcity of its main larval food by exploiting alternative food sources.展开更多
Actin filaments (AFs) in un-fixed pollen tubes of Amaryllis vittata Ait were visualized after TRITC-phalloidin staining with DMSO as a permeabilising agent. Typically, strands or hundles of microfilaments (Mfs) were d...Actin filaments (AFs) in un-fixed pollen tubes of Amaryllis vittata Ait were visualized after TRITC-phalloidin staining with DMSO as a permeabilising agent. Typically, strands or hundles of microfilaments (Mfs) were distributed in the extreme tip as well as pollen tubes in a form of network.Fluorescent granules or circles of various sizes were frequently found that continued with the filamentous structures. In addition, a more brightly stained structure, possibly Mf organizing center, was observed. Treatment of pollen tubes with cytochalasin D(CD)for increasing time intervals (5-40 minutes) caused gradual reduction of strands until flurescent granules filled up the pollen tubes. Mcanwhile, cytoplasmie streaming was inhibited completely. Though closely associated with vegetative nuclei (VN) and generative cells (GC), AFs were not found in the cytoplasm of GC.Mg++concentration greatly affected the isolated Mfs.展开更多
文摘Dynamin, a 100-kD GTPase first found in animal cells, is essential for vesicle formation in receptor-mediated endocytosis, synaptic vesicle recycling, and possibly vesicle trafficking in and out of the Golgi apparatus. Recently, dynamin-like proteins were also found in some plant cells. We demonstrate here the presence of dynamin with molecular weight of 100 kD in day-lily ( Hemerocallis fulva) pollen based on molecular estimation and Western blotting. The highly purified pollen Dynamin had GTPase activity, which could be stimulated 1.64 fold by calf brain microtubules in vitro. The results from electron microscopic examination showed that the pollen dynamin readily self-assembled into ring-like structures.
文摘Habitat fragmentation is a major threat for beneficial organisms and the ecosys- tem services they provide. Multiple-habitat users such as wild bees depend on both nesting and foraging habitat. Thus, they may be affected by the fragmentation of at least two habitat types. We investigated the effects of landscape-scale amount of and patch isolation from both nesting habitat （woody plants） and foraging habitat （specific pollen sources） on the abundance and diet of Osmia bicornis L. Trap-nests of O. bicornis were studied in 30 agricultural landscapes of the Swiss Plateau. Nesting and foraging habitats were mapped in a radius of 500 m around the sites. Pollen composition of larval diet changed as isolation to the main pollen source, Ranunculus, increased, suggesting that （9. bicornis adapted its foraging strategy in function of the nest proximity to main pollen sources. Abundance of O. bicornis was neither related to isolation or amount of nesting habitat nor to isolation or abundance of food plants. Surprisingly, nests ofO. bicornis contained fewer larvae in sites at forest edge compared to isolated sites, possibly due to higher parasitism risk. This study indicates that O. bicornis can nest in a variety of situations by compensating scarcity of its main larval food by exploiting alternative food sources.
文摘Actin filaments (AFs) in un-fixed pollen tubes of Amaryllis vittata Ait were visualized after TRITC-phalloidin staining with DMSO as a permeabilising agent. Typically, strands or hundles of microfilaments (Mfs) were distributed in the extreme tip as well as pollen tubes in a form of network.Fluorescent granules or circles of various sizes were frequently found that continued with the filamentous structures. In addition, a more brightly stained structure, possibly Mf organizing center, was observed. Treatment of pollen tubes with cytochalasin D(CD)for increasing time intervals (5-40 minutes) caused gradual reduction of strands until flurescent granules filled up the pollen tubes. Mcanwhile, cytoplasmie streaming was inhibited completely. Though closely associated with vegetative nuclei (VN) and generative cells (GC), AFs were not found in the cytoplasm of GC.Mg++concentration greatly affected the isolated Mfs.
