Effect of 2,4‐dichlorophenoxyacetic acid on polysomal profiles and polyadenylated RNA in excised tuber tissue of Jerusalem artichoke (Helianthus tuberosus)

Abstract

Dormant tuber tissue of Jerusalem artichoke (Helianthus tuberosus L.) can be stimulated by wounding to initiate RNA and protein synthesis. No DNA synthesis or cell divisions occur unless an auxin is provided. Changes in polysomal profiles and levels of Poly(A)+‐RNA in response to wounding and auxin treatment were studied. Polysomes were isolated at various times after excision and incubation of tissue in the presence or absence of 10−5M 2,4‐dichlorophenoxyacetic acid. Polysomal profiles were studied by sucrose density gradient centrifugation. Dormant tissue contained ribosomes mainly in monosome form. Within 4 h of excision, a significant increase in the polysomal fraction was observed both in control and auxin‐treated tissue. Increases in polysomes continued during the next 20 h. Poly(A)+‐RNA was isolated from total polysomal RNA by oligo(dT)‐cellulose column chromatography. There was a large increase in the amount of poly(A)+‐RNA within 4 h of excision. During the first 43 h of incubation, levels of total polysomal RNA as well as poly(A)+‐RNA in tissue treated with 2,4‐dichlorophenoxyacetic acid were significantly higher than those in controls.