Bot. Bull. Acad. Sin. (1995) 36: 73-79

Liu and Lee — In vitro binding of gibberellin A4 in epicotyls of dwarf pea

In vitro binding of gibberellin A4 in epicotyls of dwarf pea

Zin-Huang Liu1 and Bor-Heng Lee

Department of Biology, Institute of Life Sciences, National Sun Yat-sen University, Kaohsiung, Taiwan, ROC

(Received June 30, 1994; Accepted December 16, 1994)

Abstract. In vitro gibberellin (GA) binding properties of a cytosol fraction from epicotyls of dwarf pea (Pisum sativum L. cv. Progress No. 9) were investigated using [3H]GA4 in a DEAE filter paper assay at 4°C. The binding obtained is saturable, reversible, and temperature labile in dwarf pea, and has a half-life of dissociation of 5-6 min. By varying the concentration of [3H]GA4 in the incubation medium, the Kd was estimated to be 130 nM. The number of binding sites (n) was estimated to be 0.66 pmole mg-1 soluble protein. In competition binding assays, biologically active GAs, such as GA3 and GA4, could compete with [3H]GA4 for binding sites more successfully than could the biologically inactive GA4 methyl ester or epi-GA4. The influence of light on gibberellin-binding proteins in dwarf pea was also studied. The Kd and n of the GA-binding proteins for [3H]GA4 in light-treated tissues were close to the values for Kd and n in the dark grown tissues—light has little influence on gibberellin A4-binding proteins.

Keywords: GA-binding proteins; Gibberellin; Pisum sativum.

1Corresponding authors.