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

The expression analysis of the four polygalacturonase-inhibiting protein (Pgip) genes composing the bean (Phaseolus vulgaris L.) Pgip family showed a pattern 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 demuthianum. qRT-PCR analyses showed that the transcript 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 pattern was similar in the pathosystems bean-S. sclerotiorum, 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 transient transcript accumulation, with Pvpgip2 exhibiting an earlier and higher induction. These results extend previous analyses of the whole Pup gip transcript and provide additional evidences of the relevant role of PvPGIP2 in plant defence.