SUMMARY The expression analysis of the four polygalactur- onase-inhibiting protein (Pgip) genes composing the bean (Phaseolus vulgaris L.) Pgip family showed a pat- tern of transcriptional variation in young leaves, hypocotyls, roots and pods with Pvpgip1 not expressed, Pvpgip2 expressed in all organs, Pvpgip3 and Pvpgip4 poorly expressed in roots. We compared also transcript accumulation of the four Pvpgip genes during infection of bean plants with the fungal pathogens Botrytis cinerea, Sclerotinia sclerotiorum and Colletotrichum lin- demuthianum. qRT-PCR analyses showed that the tran- script level of Pvpgip1, Pvpgip2 and Pvpgip3 increases significantly following fungal infection, whereas Pvpgip4 remains unchanged. The level of induction was different between the three genes, Pvpgip2 exhibiting the strongest transcript accumulation. The induction pat- tern was similar in the pathosystems bean-S. sclerotio- rum, bean-B. cinerea, and in the compatible interaction bean-C. lindemuthianum, with a maximum of transcript accumulation in the late stage of infection. Instead, in the incompatible interaction bean-C. lindemuthianum, Pvpgip1, Pvpgip2 and Pvpgip3 showed an early and tran- sient transcript accumulation, with Pvpgip2 exhibiting an earlier and higher induction. These results extend previous analyses of the whole Pvpgip transcript and provide additional evidences of the relevant role of PvPGIP2 in plant defence. Key words: polygalacturonase-inhibiting protein (PGIP), gene family, quantitative real-time polymerase chain reaction, Phaseolus vulgaris, fungal pathogens. INTRODUCTION During infection and colonization of the plant tissue, pathogens produce a number of molecules to surmount Corresponding author: R. D’Ovidio Fax: +39.0761.357238 E-mail: dovidio@unitus.it the host barriers. Among these, cell wall degrading en- zymes (CWDEs) represent important pathogenicity fac- tors for several pathogens. Endopolygalacturonases (PGs; EC 3.2.1.15) are some of the first CWDEs secreted during the infection process. They cleave the α-(1->4) linkages between D-galacturonic acid residues in homo- galacturonan causing cell separation and maceration of host tissue. The importance of PG in pathogenesis has been demonstrated for some fungal pathogens, including Botrytis cinerea (ten Have et al., 1998), Alternaria citri (Is- shiki et al., 2001) and Claviceps purpurea (Oeser et al., 2002). The activity of this enzyme is inhibited by the polygalacturonase-inhibiting protein (PGIP) and the overexpression of this inhibitor in transgenic plants showed a significant reduction of disease symptom devel- opment caused by several fungal pathogens (Powell et al., 2000; Ferrari et al., 2003; Aguero et al., 2005; Manfre- dini et al., 2006; Joubert et al., 2006; Janni et al., 2008). PGIPs are plant cell wall glycoproteins that belong to the superfamily of leucine-rich repeat proteins (LRRs) of the extracytoplasmic type (Jones and Jones, 1997). The genes encoding these proteins have been characterized in a number of plants, including both monocot and dicot species, and in all these species the deduced encoded product is composed by 9-10 imperfect LRRs of 24 residues each (D’Ovidio et al., 2004a). These analyses showed also inter-specific variation in the number of Pgip genes per genome, ranging from 2 in Arabidopsis thaliana (Ferrari et al., 2003) to 16 in Brassica napus (Hegedus et al., 2008). Furthermore, the Pgip genes showed inter- and intra-specific variation in the transcriptional regulation and inhibition properties against fungal and insect PGs (De Lorenzo et al., 2001; D’Ovidio et al., 2004a; Federici et al., 2006; Protsenko et al., 2008). The Pgip family of common bean (Phaseolus vulgaris) is one of the best studied such families. The full comple- ment comprises four clustered genes of about 1 kbp each (Pvpgip1, Pvpgip2, Pvpgip3, Pvpgip4) oriented in the same direction and spanning a 50 kbp region (D’O- vidio et al., 2004b) on the linkage group B2 (Geffroy et al., 2000). Genomic arrangement and sequence similari- ties (>80% at nucleotide level) between the four bean Pgip genes suggested that they derive from a common ancestor through a sequence of duplication-divergence- Journal of Plant Pathology (2011), 93 (1), 141-148 Edizioni ETS Pisa, 2011 141 TRANSCRIPT ANALYSIS OF THE BEAN POLYGALACTURONASE INHIBITING PROTEIN GENE FAMILY REVEALS THAT PVPGIP2 IS EXPRESSED IN THE WHOLE PLANT AND IS STRONGLY INDUCED BY PATHOGEN INFECTION R.M. Kalunke 1 , M. Janni 1 , L. Sella 2 , P. David 3 , V. Geffroy 3,4 , F. Favaron 2 and R. D’Ovidio 1 1 Dipartimento di Agrobiologia e Agrochimica, Università della Tuscia, 01100 Viterbo, Italy 2 Dipartimento Territorio e Sistemi Agro-Forestali, Sezione Patologia Vegetale, Università degli Studi di Padova, 35020 Legnaro (PD), Italy 3 Institut de Biologie des Plantes, UMR-CNRS 8618, bât. 630, Université Paris-Sud, 91405 Orsay, France 4 Unité Mixte de Recherche de Génétique Végétale, Institut National de la Recherche Agronomique, 91190 Gif-sur-Yvette, France