The promoter of a gene encoding a polygalacturonase-inhibiting protein of Phaseolus vulgaris L. is activated by wounding but not by elicitors or pathogen infection.

Abstract

Polygalacturonase-inhibiting proteins (PGIPs), leucine-rich repeat (LRR) proteins evolutionarily related to several plant resistance genes, bind to and regulate the action of fungal endopolygalacturonases. In Phaseolus vulgaris L., PGIPs are encoded by a gene family comprising at least five members. As a start for a systematic analysis of the regulation of the pgip family, we have analysed the ability of the promoter of the bean gene pgip-1 to direct expression of beta-glucuronidase (GUS) in transfected tobacco protoplasts, microbombarded bean and tobacco leaves, and transgenic tobacco plants. In protoplasts, the pgip-1 gene region from nucleotide (nt) -2004 to nt +27 directed a level of expression that was as high as that directed by the cauliflower mosaic virus (CaMV) 35S promoter and could not be further induced by elicitor treatment; alteration of the region immediately following the TATAA sequence at nt -29 abolished expression. Upon stable integration into tobacco plants of the pgip-1 promoter-GUS construct, as well as of a -394 deletion, expression was detected for both constructs mainly in the stigma and, to a lesser extent, in the anthers and in the conductive vascular tissue. The promoter responded to wounding but not to oligogalacturonides, fungal glucan, salicylic acid, cryptogein, or pathogen infection. This expression pattern does not mirror that of the whole pgip gene family.