Auxin-binding proteins without KDEL sequence in the moss Funaria hygrometrica.
Whereas the important plant growth regulator auxin has multiple effects in flowering plants, it induces a specific cell differentiation step in the filamentous moss protonema. Here, we analyse the presence of classical auxin-binding protein (ABP1) homologues in the moss Funaria hygrometrica. Microsomal membranes isolated from protonemata of F. hygrometrica have specific indole acetic acid-binding sites, estimated to be about 3-5 pmol/mg protein with an apparent dissociation constant (K (d)) between 3 and 5 microM. Western analyses with anti-ABP1 antiserum detected the canonical endoplasmic reticulum (ER)-localised 22-24 kDa ABP1 in Zea mays, but not in F. hygrometrica. Instead, polypeptides of 31-33 and 46 kDa were labelled in the moss as well as in maize. In F. hygrometrica these proteins were found exclusively in microsomal membrane fractions and were confirmed as ABPs by photo-affinity labelling with 5-azido-[7-(3)H]-indole-3-acetic acid. Unlike the classical corn ABP1, these moss ABPs did not contain the KDEL ER retention sequence. Consistently, the fully sequenced genome of the moss Physcomitrella patens, a close relative of F. hygrometrica, encodes an ABP1-homologue without KDEL sequence. Our study suggests the presence of putative ABPs in F. hygrometrica that share immunological epitopes with ABP1 and bind auxin but are different from the classical corn ABP1.
Panigrahi
Kishore C S
KC
Max-Plank Institute for Plant Breeding Research, Cologne, Germany. panigrah@mpiz-koeln.mpg.de
Panigrahy
Madhusmita
M
Vervliet-Scheebaum
Marco
M
Lang
Daniel
D
Reski
Ralf
R
Johri
Man Mohan
MM
D000595:Amino Acid Sequence; D019068:Bryopsida / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D007210:Indoleacetic Acids / Q000378:metabolism*; D008861:Microsomes / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D010936:Plant Extracts; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
D007210:Indoleacetic Acids; D010936:Plant Extracts; D010940:Plant Proteins; D011956:Receptors, Cell Surface