Invertase Activity and the Kinetin-Stimulated Enlargement of Detached Radish Cotyledons

Abstract

Cytokinin treatment is known to promote expansion of light-grown excised radish (Raphanus sativus L. cv Crimson Giant) cotyledons. This expansion, at least in part, seems to be related to an increased accumulation of osmotically active reducing sugars. Kinetin treatment did not cause increased levels of isocitrate lyase activity over the controls, but stimulated increased levels of two invertase forms, designated types I and II. Type I was soluble and type II was insoluble after homogenization in 10 millimolar tris(hydroxymethyl)aminomethane-HCl (pH 7.0). Both types were soluble after homogenization in 300 millimolar NaCI. At low salt concentration, type II was retained on a diethylamioethyl-cellulose column and type I was not. Type II was then eluted from the column at high salt concentration. Types I and II exhibited pH optima of 53 and 43, Michaelis constants of 4.96 and 1.23 millimolar sucrose, and molecular weights of 65,000 and 57,000 daltons, respectively. The kinetin promotion of reducing sugar accumulation may be related to increased levels of the two invertase forms, but is probably not a result of direct cytokinin-stimulated glyoxysomal activity.

Antisense Acid Invertase (TIV1) Gene Alters Soluble Sugar Composition and Size in Transgenic Tomato Fruit

“…As cell enlargement declines, the concentration of hexose decreases and Suc increases. It is not clear in these studies whether acid invertase promotes cell expansion energetically (Ricardo and ap Rees, 1970) or through increased osmotically active sugars (Howard and Witham, 1983).…”

Invertase activity in sinks undergoing cell expansion

“…Cytokinins also inhibited invertase synthesis in sugar cane stem segments, but its effects were unspecific [7] . Cytokinins promote expansion in excised, light-grown radish cotyledons [27] and this expansion is associated with an increase in the concentration of reducing sugars [20] and a rise in acid invertase activity [ 19] .…”

“…In a number of systems the stimulation of growth and acid invertase activity by exogenous growth regulators is prevented by prior or simultaneous treatment with inhibitors of mRNA or protein synthesis [11,46,23,24,40 ;Morris and Arthur,unpublished] . Several authors have suggested that de novo synthesis of invertase may occur in response to growth regulator treatments [46,24,19] . Detailed studies of acid invertase synthesis in sugar cane stem tissues led to the conclusion that both GA 3 and auxins (IAA and NAA) stimulated synthesis of the enzyme by stabilizing pre-formed invertase mRNA [7, 111 . However, other claims for de novo initiation of invertase synthesis by growth regulators require more rigorous examination .…”

EFFECT OF GROWTH REGULATORS ON THE IN VITRO GERMINATION AND TUBE GROWTH OF MAIZE (ZEA MA YS L.) POLLEN FROM PLANTS RAISED UNDER SODIUM CHLORIDE SALINITY

“…This adduces support to the ohservation of Levitt (1980) that stressed plants respond more to BAP than unstressed plants. The enhancement of pollen germination and tube growth by BAP is possibly due to its effect on the enhanced incorporation of amino acids into proteins under saline conditions (Kahane & Poljakoff-Mayber, 1968;Singh & Singh, 1980) or to the increased invertase activity in pollen which would provide precursors for pollen tube wall synthesis as reported for chicory roots (Rutherford & Bard, 1971) and radish cotyledons (Howard & Witham, 1983).…”