AtMinD also contains a putative chloroplast transit peptide. To correlate FtsZ protein levels with the transgenic phenotypes and provide sensitive probes for expression and localization studies, antisera are being raised against peptides designed to mimic optimal FtsZ epitopes. This suggests that AtftsZ2-1 can interact with the bacterial division apparatus. Our data collectively imply that plastid and prokaryotic cell division are evolutionarily and mechanistically related, but that the processes mediating plastid division are inherently more complex. In many gravitropism experiments, the light came from above, a configuration that could exaggerate the effect of gravitropism if phototropism were not taken into account.
Many data indicate that starch-filled amyloplasts trigger gravitropic sensing.
These results demonstrate that starch is not necessary for some gravitropism but is required for full sensitivity. However, these data were obtained with light from above and thus it is possible that the contribution of root phototropism led to an overestimate of the gravitropic sensitivity of either or both genotypes. By accounting for the contribution of root phototropism, the pgm-1 mutant was found to be significantly less sensitive to gravity than the WT compared to previous estimates. These results provide additional support for the importance of amyloplasts in gravitropic sensing and also point to the need for consideration of light position in the design of gravitropism experiments. The presumptive gravity sensing cells of the root and stem were examined to determine whether the mutation altered gravitropism, amyloplast sedimentation and starch content.