Polygalacturonase-inhibiting proteins (PGIPs) are extracellular plant inhibitors of fungal endopolygalacturonases (PGs) that\ud belong to the superfamily of Leu-rich repeat proteins. We have characterized the full complement of pgip genes in the bean\ud (Phaseolus vulgaris) genotype BAT93. This comprises four clustered members that span a 50-kb region and, based on their\ud similarity, form two pairs (Pvpgip1/Pvpgip2 and Pvpgip3/Pvpgip4). Characterization of the encoded products revealed both\ud partial redundancy and subfunctionalization against fungal-derived PGs. Notably, the pair PvPGIP3/PvPGIP4 also inhibited\ud PGs of two mirid bugs (Lygus rugulipennis and Adelphocoris lineolatus). Characterization of Pvpgip genes of Pinto bean showed\ud variations limited to single synonymous substitutions or small deletions. A three-amino acid deletion encompassing a residue\ud previously identified as crucial for recognition of PG of Fusarium moniliforme was responsible for the inability of BAT93\ud PvPGIP2 to inhibit this enzyme. Consistent with the large variations observed in the promoter sequences, reverse\ud transcription-PCR expression analysis revealed that the different family members differentially respond to elicitors, wounding,\ud and salicylic acid. We conclude that both biochemical and regulatory redundancy and subfunctionalization of pgip genes are\ud important for the adaptation of plants to pathogenic fungi and phytophagous insects

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Polygalacturonase-inhibiting proteins (PGIPs) are leucine-rich repeat (LRR) proteins that inhibit fungal endopolygalacturonases (PGs). They are encoded by multigene families whose members show functional redundancy and subfunctionalization for recognition of fungal PGs. In order to expand the information on the structure and functional features of legume PGIP, we have isolated and characterized four members of the soybean Pgip gene family and determined the properties of the encoded protein products. Sequence analysis showed that these genes form two clusters: one cluster of about 5 kbp containing Gmpgip1 and Gmpgip2, and the other containing Gmpgip3 and Gmpgip4 within a 60 kb fragment of a separate BAC clone. Sequence diversification of the four members resides mainly in the xxLxLxx region that includes residues forming the beta-sheet B1. When compared with other legume Pgip genes, Gmpgip3 groups with the bean genes Pvpgip1 and Pvpgip2, suggesting that these genes are closer to the ancestral gene. At the protein level, only GmPGIP3 shows the capability to inhibit fungal PGs. The spectrum of inhibition of GmPGIP3 against eight different fungal PGs mirrors that of the PGIP purified from soybean tissues and is similar to that of the bean PvPGIP2, one of the most efficient inhibitors so far characterized. We also report that the four Gmpgip genes are differentially regulated after wounding or during infection with the fungal pathogen Sclerotinia sclerotiorum. Following fungal infection Gmpgip3 is up regulated promptly, while Gmpgip2 is delayed.

Polygalacturonase-inhibiting proteins (PGIPs) are leucine-rich repeat (LRR) proteins involved in plant defence. A number of PGIPs have been characterized from dicot species, whereas only a few data are available from monocots. Database searches and genome-specific cloning strategies allowed the identification of four rice (Oryza sativa L.) and two wheat (Triticum aestivum L.) Pgip genes. The rice Pgip genes (Ospgip1, Ospgip2, Ospgip3 and Ospgip4) are distributed over a 30 kbp region of the short arm of chromosome 5, whereas the wheat Pgip genes, Tapgip1 and Tapgip2, are localized on the short arm of chromosome 7B and 7D, respectively. Deduced amino acid sequences show the typical LRR modular organization and a conserved distribution of the eight cysteines at the N- and C-terminal regions. Sequence comparison suggests that monocot and dicot PGIPs form two separate clusters sharing about 40% identity and shows that this value is close to the extent of variability observed within each cluster. Gene-specific RT-PCR and biochemical analyses demonstrate that both Ospgips and Tapgips are expressed in the whole plant or in a tissue-specific manner, and that OsPGIP1, lacking an entire LRR repeat, is an active inhibitor of fungal polygalacturonases. This last finding can contribute to define the molecular features of PG-PGIP interactions and highlights that the genetic events that can generate variability at the Pgip locus are not only limited to substitutions or small insertions/deletions, as so far reported, but can also involve variation in the number of LRRs.

Polygalacturonase-inhibiting proteins (PGIPs) are plant defence molecules inhibiting the activity of fungal endo-polygalacturonases (endo-PGs). We found that soybean and bean PGIPs inhibited the endo-PG activity produced by the isolate FC-10 of Fusarium moniliforme but not the enzyme activity produced by the isolate PD of F. moniliforme. The bean PGIP proved to be ineffective against all the PG isoforms produced by the PD isolate. Deduced amino acid sequence comparison between PGs from PD, FC-10 and 62264 isolates identified the structural regions of the enzyme possibly related to its resistance to PGIP inhibition. These include one region at the N-terminal portion of the enzyme and a few single amino acid substitutions along the entire sequence, two of which surrounding the active site.