Plant Cell Rep (2009) 28:1747–1758 DOI 10.1007/s00299-009-0775-2 O R I G I N A L P A P E R Auxin-binding proteins without KDEL sequence in the moss Funaria hygrometrica Kishore C. S. Panigrahi • Madhusmita Panigrahy • Marco Vervliet-Scheebaum • Daniel Lang • Ralf Reski • Man Mohan Johri Received: 22 July 2009 / Revised: 4 September 2009 / Accepted: 16 September 2009 / Published online: 2 October 2009 The Author(s) 2009. This article is published with open access at Springerlink.com Abstract 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 (Kd) between 3 and 5 lM. 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. hy- grometrica these proteins were found exclusively in Communicated by P. Kumar. K. C. S. Panigrahi (&) Max-Plank Institute for Plant Breeding Research, Carl-von-Linne-Weg 10, 50829 Cologne, Germany e-mail: panigrah@mpiz-koeln.mpg.de M. Panigrahy Directorate of Rice Research, Rajendranagar, Hyderabad, Andhra Pradesh 500028, India M. Vervliet-Scheebaum D. Lang R. Reski Plant Biotechnology, Faculty of Biology, University of Freiburg, Schaenzlestrasse 1, 79104 Freiburg, Germany R. Reski Centre for Biological Signalling Studies (bioss), University of Freiburg, Albertstrasse 19, 79104 Freiburg, Germany M. M. Johri 32 New Cosmos, Juhu-Versova Link Road, Andheri (W), Mumbai 400053, India microsomal membrane fractions and were conﬁrmed as ABPs by photo-afﬁnity labelling with 5-azido-[7-3H]- 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. hy- grometrica, encodes an ABP1-homologue without KDEL sequence. Our study suggests the presence of putative ABPs in F. hygrometrica that share immunological epi- topes with ABP1 and bind auxin but are different from the classical corn ABP1. Keywords ABP1 Photo-afﬁnity labelling Phytohormone Physcomitrella patens Signalling Zea mays Abbreviations IAA Indole-3-acetic acid ER Endoplasmic reticulum Introduction Changes in the development of land plants are usually reg- ulated by phytohormones (Davies 1995). Auxin, as the most prominent one, acts as growth regulator thus being involved in a variety of developmental and physiological processes in a tissue speciﬁc manner such as speciﬁcation of root and shoot, cell elongation and cell division (Weijers and Jurgens 2005; Willemsen and Scheres 2004). Auxin is ubiquitous in heterotrophic and photoautotrophic organisms; besides from seed plants, its presence has been conﬁrmed in algae, bryo- phytes and ferns (Evans and Trewavas 1991). In algae and 123