Ethylene-dependent effects on generative organ abscission of Lupinus luteus

The abscission of certain organs from the plant is part of the fulfilment of its developmental programs. The separation process occurs in a specialized abscission zone usually formed at the base of detached organ. The changing level of phytohormones, particularly ethylene, is the element responsible for coordinating anatomical and physiological transformation that accompanies organ abscission. The application of ethylene (ET) on Lupinus luteus stimulates flower abortion. However, the treatment with 1-aminocyclopropane-1-carboxylic acid (ACC) – direct ET precursor – does not cause such a strong physiological response. In turn, when applied on the pedicels both ET biosynthesis (2-aminoethoxyvinylglycine; AVG) and action (norbornadiene; NBD) inhibitors reversed the stimulatory effect of ET on generative organ separation. In order to determine ET role in the flower abscission process in L. luteus, we identified the sequences coding for synthase (LlACS) and oxidase (LlACO) of ACC and measured their expression levels. Abscission zone activation is accompanied by a considerable increase both in LlACS and LlACO cDNAs and also ACC content, which is specifically localized in the dividing cells at the base of the flower being detached. Obtained results suggest that ET is a strong stimulator of flower abortion in L. luteus.