Characterization and use in ELISA of a new monoclonal antibody for quantitation of abscisic acid in senescing rice leaves

A new monoclonal antibody (mAb) was generated against abscisic acid (ABA), and an indirect enzyme-linked immunosorbent assay (ELISA) using this mAb was developed for convenient quantitative analysis of ABA levels in rice leaf extracts. The mAb, raised against (+-)-ABA conjugated to bovine serum albumin (BSA) through its carboxyl group (C₁), reacted preferentially with the (+)-ABA enantiomer, and equally well with both free and methyl-ester (+-)-ABA. Cross-reactivity with several ABA-related compounds was negligible. Linearity was obtained between 3 and 1000 pmo1 of (+)-ABA. The ABA-mAb was further used to quantitate pmol quantities of (+)-ABA in attached and detached rice leaves. Results obtained with such ELISA quantitation showed an increase in the free ABA content of detached rice leaves at progressive stages of senescence, which was regarded as a senescence-related response. This quantitation compared favorably with other presently used techniques for ABA determination, with regard to their detection limits, cost and assay time. The results suggest that the combination of a specific mAb with a sensitive ELISA technique is quite promising for quantitation of ABA.