Interaction of [3H]gibberellin A1 with a sub-cellular fraction from lettuce (Lactuca sativa L.) hypocotyls

The relationship between protein synthesis and the incorporation of ³H]gibberellin A₁ (³H]GA₁) into a 2,000xg pelletable (2KP) fraction from lettuce (Lactuca sativa L.) hypocotyl sections has been investigated. Concentrations of D-2-(4-methyl-2,6-dinitroanilino)-N-methylpropionamide (MDMP) between 10^-7 M and 10^-4 M caused increasing inhibition of growth, 2KP labelling and incorporation of ¹⁴C]leucine into soluble protein. Growth and 2KP radioactivity were highly correlated (r=0.996). Transfer to MDMP early or late in the course of GA response caused reductions in both growth and incorporation into the 2KP fraction. Exposure to the inhibitor had more effect at 4 h than at 20 h. The proportions of alkali-soluble and insoluble radioactivity in the 2KP fraction were also altered by this treatment. The implications of these findings are discussed.Abbreviations GA₁ gibberellin A₁ - MDMP D-2-(4-methyl-2,6-dinitroanilino)-N-methylpropionamide - 2KP a2,000xg pelletable fraction