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Regulation of membrane trafficking and organ separation by the NEVERSHED ARF-GAP protein
Sarah J. Liljegren, Michelle E. Leslie, Lalitree Darnielle, Michael W. Lewis, Sarah M. Taylor, Ruibai Luo, Niko Geldner, Joanne Chory, Paul A. Randazzo, Martin F. Yanofsky, Joseph R. Ecker


Cell separation, or abscission, is a highly specialized process in plants that facilitates remodeling of their architecture and reproductive success. Because few genes are known to be essential for organ abscission, we conducted a screen for mutations that alter floral organ shedding in Arabidopsis. Nine recessive mutations that block shedding were found to disrupt the function of an ADP-ribosylation factor-GTPase-activating protein (ARF-GAP) we have named NEVERSHED (NEV). As predicted by its homology to the yeast Age2 ARF-GAP and transcriptional profile, NEV influences other aspects of plant development, including fruit growth. Co-localization experiments carried out with NEV-specific antiserum and a set of plant endomembrane markers revealed that NEV localizes to the trans-Golgi network and endosomes in Arabidopsis root epidermal cells. Interestingly, transmission electron micrographs of abscission zone regions from wild-type and nev flowers reveal defects in the structure of the Golgi apparatus and extensive accumulation of vesicles adjacent to the cell walls. Our results suggest that NEV ARF-GAP activity at the trans-Golgi network and distinct endosomal compartments is required for the proper trafficking of cargo molecules required for cell separation.


  • We thank M. Peifer, J. Reed, J. Kieber, M. Duncan, V. Bautch, S. Patterson, V. Bankaitis and C. Jones for helpful discussions; V. Madden (UNC Microscopy Services) and T. Perdue (UNC Biology Microscopy) for assistance with TEM, SEM and confocal microscopy; S. Guimil, C. Habbersett, A. Imler, D. Reyes and R. Weaver for assistance with mutant screens and mapping; P. Pinyopich for the nev-3 allele; T. Jack, Y. Eshed and J. Bowman for enhancer trap lines; and Monsanto for access to Ler polymorphisms. This research was primarily supported by an NSF grant and UNC startup funds to S.J.L.; the early stages of the project were funded by grants from USDA to S.J.L., NSF and DOE to J.R.E., and NSF to M.F.Y.; generation of the Wave markers was supported by funding from NSF, USDA and HHMI to J.C. M.E.L. was supported by a William R. Kenan Fellowship and the UNC Curriculum in Genetics and Molecular Biology, and M.W.L. by the NIH-funded UNC Developmental Biology training program. P.A.R. and R.L. are supported by the Intramural Program of the National Cancer Institute, NIH, Department of Health and Human Services. Deposited in PMC for release after 6 months.

    • Accepted March 25, 2009.
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