tailieunhanh - báo cáo khoa học: " Mechanistic insights from a quantitative analysis of pollen tube guidance"

Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành y học dành cho các bạn tham khảo đề tài: Mechanistic insights from a quantitative analysis of pollen tube guidance | Stewman et al. BMC Plant Biology 2010 10 32 http 1471-2229 10 32 BMC Plant Biology RESEARCH ARTICLE Open Access Mechanistic insights from a quantitative analysis of pollen tube guidance Shannon F Stewman1 2 9 Matthew Jones-Rhoades7 Prabhakar Bhimalapuram8 Martin Tchernookov2 6 Daphne Preuss3 4 5 Aaron R Dinner1 2 5 Abstract Background Plant biologists have long speculated about the mechanisms that guide pollen tubes to ovules. Although there is now evidence that ovules emit a diffusible attractant little is known about how this attractant mediates interactions between the pollen tube and the ovules. Results We employ a semi-in vitro assay in which ovules dissected from Arabidopsis thaliana are arranged around a cut style on artificial medium to elucidate how ovules release the attractant and how pollen tubes respond to it. Analysis of microscopy images of the semi-in vitro system shows that pollen tubes are more attracted to ovules that are incubated on the medium for longer times before pollen tubes emerge from the cut style. The responses of tubes are consistent with their sensing a gradient of an attractant at 100-150 pm farther than previously reported. Our microscopy images also show that pollen tubes slow their growth near the micropyles of functional ovules with a spatial range that depends on ovule incubation time. Conclusions We propose a stochastic model that captures these dynamics. In the model a pollen tube senses a difference in the fraction of receptors bound to an attractant and changes its direction of growth in response the attractant is continuously released from ovules and spreads isotropically on the medium. The model suggests that the observed slowing greatly enhances the ability of pollen tubes to successfully target ovules. The relation of the results to guidance in vivo is discussed. Background In flowering plants unlike animals the male and female germ units are multicellular haploid structures that develop in .