Monoclonal antibodies for the detection and quantitation of the endogenous plant growth regulator, abscisic acid

Abstract

Monoclonal antibodies (mAB) have been produced which recognize the physiologically active 2‐ cis ‐( S ‐form of the endogenous plant growth regulator, abscisic acid (ABA). Cross‐reaction with the ABA‐catabolites, phaseic and dihydrophaseic acid, is negligible, and ( R )‐ABA, 2‐ trans ‐ABA, the ABA‐conjugate, ABA‐β‐D‐glucopyranosyl ester, as well as the putative ABA precursor, xanthoxin, are totally unreactive. In addition to being very specific, the mAB exhibit high affinites for 2‐ cis ‐( S )‐ABA: the K values were 7.9 × 10 9 l/mol and 3.7 × 10 9 l/mol for antibodies from two different clones. By mAB‐radioimmunoassay (RIA), 4 pg 2‐ cis ‐( S )‐ABA (99.5% confidence level) can be detected. mAB‐RIA can be used to quantitate ABA directly in unprocessed plant extracts.