Effect of Auxin on Autolysis of Cell Walls in Azuki Bean Epicotyls

Native cell walls of azuki bean epicotyls incubated in bufferautolytically released neutral sugars, abundant in galactose,and uronic acids. Treatment with 10^–5 M IAA of subapicalor basal epicotyl segments for 3 h did not influence the amountof total neutral sugars released from the cell walls duringautolysis. However, the amount of glucose and xylose releasedfrom subapical cell walls was increased by IAA. Pretreatmentwith IAA of subapical epicotyl segments enhanced the solubilizationof neutral sugars from pectinase-treated cell walls during incubationin buffer at pH 5 to 6. The amount of fucose, xylose, and glucosereleased was specifically increased by IAA. Of the sugar fractionsreleased from pectinase-treated cell walls during autolysisand subsequently separated by gel filtration on a ToyopearlHW-40S column, IAA promoted the release of oligosaccharides,consisting mainly of glucose and xylose. These results suggestthat autolytic degradation of xyloglucans is closely relatedto IAA-induced growth of azuki bean epicotyls. (Received May 19, 1989; Accepted January 5, 1990)