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Auxin-binding proteins without KDEL sequence in the moss Funaria hygrometrica
Kishore C S Panigrahi1, Madhusmita Panigrahy, Marco Vervliet-Scheebaum
1Max-Plank Institute for Plant Breeding Research, Cologne, Germany. panigrah@mpiz-koeln.mpg.de
Plant Cell Reports
|October 3, 2009
Summary
This study investigated auxin-binding proteins (ABPs) in the moss Funaria hygrometrica, finding proteins that bind auxin but differ from classical ABP1 found in maize. These moss ABPs lack the KDEL ER retention sequence.
Area of Science:
- Plant biology
- Molecular plant physiology
- Plant hormone signaling
Background:
- Auxin is a crucial plant growth regulator with diverse roles in flowering plants.
- In moss protonema, auxin specifically induces cell differentiation.
- The classical auxin-binding protein 1 (ABP1) is well-characterized in maize.
Purpose of the Study:
- To analyze the presence and characteristics of auxin-binding protein (ABP) homologues in the moss Funaria hygrometrica.
- To compare moss ABPs with the canonical ABP1 from maize.
- To investigate the localization and structural features of potential ABPs in F. hygrometrica.
Main Methods:
- Isolation and characterization of microsomal membranes from F. hygrometrica protonemata.
- Indole acetic acid binding assays to quantify binding sites and affinity.
- Western blot analysis using anti-ABP1 antiserum.
- Photo-affinity labeling with a labeled auxin analog.
- Bioinformatic analysis of ABP1 homologues in Physcomitrella patens.
Main Results:
- Specific indole acetic acid-binding sites were detected in F. hygrometrica microsomal membranes.
- Western blot analysis revealed 31-33 kDa and 46 kDa polypeptides in moss, distinct from maize ABP1.
- These moss polypeptides were confirmed as ABPs via photo-affinity labeling.
- Moss ABPs lacked the KDEL ER retention sequence, unlike maize ABP1.
- Genomic analysis of Physcomitrella patens confirmed ABP1 homologues without KDEL sequences.
Conclusions:
- Funaria hygrometrica possesses putative auxin-binding proteins (ABPs) that bind auxin.
- These moss ABPs share immunological epitopes with canonical ABP1 but differ structurally, notably lacking the KDEL ER retention sequence.
- The findings suggest divergent evolution of ABP1 homologues in plants, with distinct characteristics in mosses compared to flowering plants like maize.
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