Multiple Copies of Genes Encoding XEGIPs are Harbored in an 85-kB Region of the Potato Genome

Proteinaceous inhibitors of plant cell wall degrading enzymes can provide a first level of defense from invasive phytopathogens. One recently discovered inhibitor is the xyloglucans-specific endoglucanase inhibitor protein (XEGIP) originally found in tomato. This inhibitor protein has since been found in many solanaceous plants as well as other dicots. As xyloglucans play a major role in maintaining cell wall structure in dicots, protection of xyloglucan is critical. Thus far, only a single potato XEGIP had been identified (AY321357), even though a major pathogen of potato, Phytophthora infestans, has multiple copies of xyloglucan-specific endoglucanase. We now report that potato has nine additional copies of XEGIP, clustered together on a small region of chromosome one. They are located adjacent to the previously described potato XEGIP and represent one of the highest degrees of gene duplication relative to any other potato inhibitor. Synteny with tomato indicates this duplication may have occurred before speciation of Solanum.