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A cell-specific, prenylation-independent mechanism regulates targeting of type II RACs

Meirav Lavy1, Keren Bracha-Drori, Hasana Sternberg

  • 1Department of Plant Sciences, Tel Aviv University, Ramat Aviv, Tel Aviv 69978, Israel.

The Plant Cell
|October 9, 2002
PubMed

Insights

Prenylation is not essential for all RHO proteins in Arabidopsis. Three RHO proteins (AtRAC7, AtRAC8, AtRAC10) target membranes via palmitoylation, suggesting unique functions in plant cell growth.

Area of Science:

  • Plant molecular biology
  • Cell signaling
  • Protein prenylation

Background:

  • RHO proteins regulate signaling cascades and are typically prenylated for membrane association.
  • Prenylation is considered crucial for RHO protein function.
  • Eleven RHO-related proteins exist in Arabidopsis, with eight known to be prenylated.

Purpose of the Study:

  • To investigate the targeting mechanisms of prenylation-independent RHO proteins in Arabidopsis.
  • To determine the role of palmitoylation in the membrane association of AtRAC7, AtRAC8, and AtRAC10.
  • To explore the functional significance of these proteins in plant development, particularly root hair elongation.

Main Methods:

  • Identification of RHO-related proteins in Arabidopsis.
  • Enzyme assays to test prenylation of AtRAC7, AtRAC8, and AtRAC10 by farnesyltransferase and geranylgeranyltransferase I.
  • In vitro palmitoylation assays for AtRAC8.
  • Analysis of protein localization in plant cells, including root hair cells.
  • Assessment of root hair deformation in response to protein activity.

Main Results:

  • AtRAC7, AtRAC8, and AtRAC10 exhibit prenylation-independent membrane targeting.
  • Palmitoylation is essential for the plasma membrane association of these three RHO proteins.
  • AtRAC8 and AtRAC10 are not prenylated by common prenyltransferases, while AtRAC7 can be prenylated in yeast.
  • Localization of AtRAC8 and a constitutively active AtRAC7 mutant is impaired in root hair cells, affecting root hair elongation.

Conclusions:

  • AtRAC7, AtRAC8, and AtRAC10 represent a distinct class of RHO proteins in Arabidopsis.
  • Their membrane association relies on palmitoylation, not prenylation, indicating a cell-specific targeting mechanism.
  • These proteins likely possess unique functions distinct from prenylation-dependent RHO proteins, potentially impacting plant development.

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