Isolation and characterization of the proteinase inhibitor-inducing factor from tomato leaves. Identity and activity of poly- and oligogalacturonide fragments.
Mild acid hydrolysis of a small (Mr = 6 kDa) pectic polysaccharide isolated from tomato leaves, an inducer of the synthesis and accumulation of two proteinase inhibitors in excised tomato plants, yielded a alpha-D-polygalacturonic acid polymer with degree of polymerization = 20 that retained proteinase inhibitor-inducing activity. Enzymic and acid hydrolysis of this polygalacturonan yielded a series of alpha-1,4-D-galacturonic acid oligomers with degrees of polymerization from 2 to 6 which were purified to homogeneity and assayed for proteinase inhibitor-inducing activity in young excised tomato plants. All of the oligomers exhibited activity. The hexagalacturonide possessed the highest activity and the trimer the lowest. The evidence supports a possible role for plant cell wall fragments as systemic messengers that regulate the expression of proteinase inhibitor genes in plant leaves in response to pest attacks.
D002241:Carbohydrates / Q000032:analysis; D002848:Chromatography, DEAE-Cellulose; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D006603:Hexuronic Acids; D009844:Oligosaccharides / Q000032:analysis; D010368:Pectins / Q000302:isolation & purification*; D010944:Plants / Q000032:analysis*; D014574:Uronic Acids / Q000032:analysis*
D002241:Carbohydrates; D006603:Hexuronic Acids; D009844:Oligosaccharides; D014574:Uronic Acids; C043411:proteinase inhibitor-inducing factor (tomato); C007819:galacturonic acid; D010368:Pectins; C003181:polygalacturonic acid