Hormonal regulation of barley nuclease: investigation using a monoclonal antibody

Abstract. A monoclonal antibody prepared against barley (Hordeum vulgare L., cv. Himalaya) nuclease (EC 3.1.30.2) was characterized with solid‐state enzyme‐linked immunosorbent assays and immuno‐blotting. The antibody was specific for intracellular and secreted nuclease. Hormonal regulation of the synthesis and secretion of nuclease in isolated aleurone layers was investigated by immunoprecipitation of biosynthetically‐labelled nuclease using polyclonal antibodies and by immunoblot analyses using the monoclonal antibody, respectively. Gibberellic acid (GA₃) induced the de novo synthesis and secretion of nuclease in a time‐and concentration‐dependent manner. Nuclease was detected in aleurone layers incubated in 1 mmol m⁻³ GA₃, after 24 h. The maximum rates of nuclease synthesis and secretion occurred 36–48 h after hormone treatment. A minimum concentration of 10⁻⁶ mol m⁻³ GA₃ was required for nuclease synthesis and secretion, whereas the maximum rate of nuclease secretion occurred at concentrations of 10⁻⁵ mol m⁻³ and higher. In the presence of abscisic acid, the synthesis and secretion of nuclease from GA₃‐treated aleurone layers was almost completely inhibited. Based on these findings, the authors conclude that all nuclease within and secreted from aleurone layers treated with GA₃ is the result of its de novo synthesis.