Journal article
GFP Tagging of Sieve Element Occlusion (SEO) Proteins Results in Green Fluorescent Forisomes
Plant and cell physiology, Vol.49(11), pp.1699-1710
11/2008
Handle:
https://hdl.handle.net/2376/110875
PMCID: PMC2582178
PMID: 18784195
Abstract
Forisomes are Ca
2+
-driven, ATP-independent contractile protein bodies that reversibly occlude sieve elements in faboid legumes. They apparently consist of at least three proteins; potential candidates have been described previously as ‘FOR’ proteins. We isolated three genes from
Medicago truncatula
that correspond to the putative forisome proteins and expressed their green fluorescent protein (GFP) fusion products in
Vicia faba
and
Glycine max
using the composite plant methodology. In both species, expression of any of the constructs resulted in homogenously fluorescent forisomes that formed sieve tube plugs upon stimulation; no GFP fluorescence occurred elsewhere. Isolated fluorescent forisomes reacted to Ca
2+
and chelators by contraction and expansion, respectively, and did not lose fluorescence in the process. Wild-type forisomes showed no affinity for free GFP in vitro. The three proteins shared numerous conserved motifs between themselves and with hypothetical proteins derived from the genomes of
M. truncatula, Vitis vinifera
and
Arabidopsis thaliana
. However, they showed neither significant similarities to proteins of known function nor canonical metal-binding motifs. We conclude that ‘FOR’-like proteins are components of forisomes that are encoded by a well-defined gene family with relatives in taxa that lack forisomes. Since the mnemonic
FOR
is already registered and in use for unrelated genes, we suggest the acronym
SEO
(sieve element occlusion) for this family. The absence of binding sites for divalent cations suggests that the Ca
2+
binding responsible for forisome contraction is achieved either by as yet unidentified additional proteins, or by SEO proteins through a novel, uncharacterized mechanism.
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Details
- Title
- GFP Tagging of Sieve Element Occlusion (SEO) Proteins Results in Green Fluorescent Forisomes
- Creators
- Hélène C Pélissier - School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USAWinfried S Peters - Indiana/Purdue University Fort Wayne, Department of Biology, 2101 East Coliseum Boulevard, Fort Wayne, IN 46805-1499, USARay Collier - School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USAAart J. E van Bel - Institut für Allgemeine Botanik, Justus-Liebig-Universität, Senckenbergstr. 17–21, D-35390 Gießen, GermanyMichael Knoblauch - School of Biological Sciences, Washington State University, Pullman, WA 99164-4236, USA
- Publication Details
- Plant and cell physiology, Vol.49(11), pp.1699-1710
- Academic Unit
- Biological Sciences, School of
- Publisher
- Oxford University Press
- Identifiers
- 99900547184901842
- Language
- English
- Resource Type
- Journal article