About the Cover
On the Cover: In this issue, Hicks et al. (pp. 1227Ð1239) demonstrate that the tonoplast is extremely active during the biogenesis of vacuoles in germinating Arabidopsis pollen. They have also found that the vcl1 defect, which is required for vacuole formation and viability in embryos, affects the haploid gametophytes; however, the defect is not fully expressive. Surprisingly, vacuole morphology appears to be normal in vcl1 pollen indicating that the mechanism of vacuole biogenesis may differ from that in the sporophyte. It also indicates that pollen could be useful for examining pathways in which mutations are lethal to the sporophyte. The cover is an image montage of germinating pollen grains arranged in the form of a running man to convey the astonishing activity of the tonoplast. All of the images are of Arabidopsis pollen expressing the tonoplast marker δ-TIP::GFP (colored green) and viewed by laser scanning confocal microscopy. The individual images are not at an equivalent scale. Head: Transmitted image of a mature pollen grain overlaid with several features. The eyes (false-colored red) are sperm cells stained with the dye 4´,6-diamidino-2-phenylindole, whereas the mouth is tonoplast tagged with δ-TIP::GFP. Body: A mature pollen grain showing dispersed vacuoles. Arms, legs, and scarf: Germinating pollen grains with associated pollen tubes showing a range of vacuole morphology from dispersed vacuoles in the grain and tube (upper legs) to more extensive vacuolation (arms, lower legs), including a stage in which vacuoles appear intermediate in size (scarf). Bottom: The pollen man is running on lower magnification images of mature pollen grains. Cover design and preparation by Glenn Hicks and Jocelyn Brimo (University of California, Riverside).
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Copyright © 2007 by the American Society of Plant Biologists
