Plant Science 149 (1999) 125–137 Expression of genes encoding PR10 class pathogenesis-related proteins is inhibited in yellow lupine root nodules  Michal M. Sikorski a, *, Jacek Biesiadka a , Alina E. Kasperska a , Joanna Kopcin ´ ska b , Barbara Lotocka b , Wladyslaw Golinowski b , Andrzej B. Legocki a a Institute of Bioorganic Chemistry, Polish Academy of Sciences, Noskowskiego 12 /14, 61 -704 Poznan ´ , Poland b Department of Botany, Agriculture Uniersity, Rakowiecka 26 /30, 02 -528 Warsaw, Poland Received 17 May 1999; received in revised form 1 July 1999; accepted 21 July 1999 Abstract Pathogenesis-related proteins of the PR10 class have been found in many plant species, are induced under various stress conditions and act as common allergens. Here we demonstrate the presence of two PR10 proteins in yellow lupine (Lupinus luteus L. cv. Ventus). Both 17 kDa proteins, referred to as LlPR10.1A and LlPR10.1B, are composed of 156 amino acids, and have 76% parities identity (91% similarity). Identity to homologues from other plants ranges from 25 to 67% (46 – 82% similarity). Patterns of their expression in lupine organs and tissues were investigated using Western blotting and immunocytochemistry. Both proteins are constitutively expressed in roots, but expression is significantly decreased in young and mature root nodules (9 – 26 days post infection (dpi)), but not in senescent nodules (36 dpi). Immunocytochemical staining localised the proteins in the parenchymatous tissues of the root and senescent nodule, primarily in the cortex. The PR10 proteins were not detected in nodule bacteroid tissue. Expression in aerial parts of the plant is generally lower and only one of the proteins, LlPR10.1B, is expressed constitutively in the stem, leaf and petiole, while the other, LlPR10.1A, is only present in the stem and is induced in senescent leaves. © 1999 Elsevier Science Ireland Ltd. All rights reserved. Keywords: Differential expression; Immunocytochemistry; Lupinus luteus ; PR10 proteins; Protein purification; Symbiosis www.elsevier.com/locate/plantsci 1. Introduction One of the important features of plant response to stress is the increased expression of distinct proteins, including chitinases, glucanases, enzymes of phenylpropanoid pathway, thionins, osmotines, peroxidases, protease inhibitors, proteases, pro- line-rich glycoproteins and proteins of unknown function. The stress-induced proteins, described as ‘pathogenesis-related’ (PR) have been classified into 12 groups according to their properties or sequence homology [1]. Proteins of the PR10 class seem to be ubiquitous in the plant kingdom, their homologues found in various species belonging to both dicotyledonous and monocotyledonous plants [2]. Also, based on sequence homology, common allergens present in birch pollen grains [3], celery [4] and apple [5] are included in this group. The PR10 proteins are small (around 17 kDa), slightly acidic and resistant to proteases. Although a precise cellular localisation of PR10 proteins has not been determined, the absence of an apparent signal peptide and their structural properties indicate that they are cytosolic [6,7]. Tertiary structure of the birch pollen allergen Betv1 was recently determined by X-ray crystal- lography [8]. The protein contains a long C-termi- nal -helix, surrounded by a seven-stranded -sheet. Additionally, two shorter -helices are located near the N-terminus. The amino acid se-  The nucleotide sequences of the full-length cDNA clones Llpr10.1a and Llpr10.1b were registered in the EMBL GenBank under accession numbers X79974 and X79975. * Corresponding author. Tel.: +48-61-8528503; fax: +48-61- 8520532. E-mail address: mmsik@ibch.poznan.pl (M. Sikorski) 0168-9452/99/$ - see front matter © 1999 Elsevier Science Ireland Ltd. All rights reserved. PII:S0168-9452(99)00148-X