Binyamin, L., Faculty of Biology, Technion, Israel Institute of Technology, Haifa, 32000, Israel
Falah, M., Faculty of Biology, Technion, Israel Institute of Technology, Haifa, 32000, Israel
Portnoy, V., Faculty of Biology, Technion, Israel Institute of Technology, Haifa, 32000, Israel
Soudry, E., Faculty of Biology, Technion, Israel Institute of Technology, Haifa, 32000, Israel
Gepstein, S., Faculty of Biology, Technion, Israel Institute of Technology, Haifa, 32000, Israel

To better understand the genetic controls of leaf senescence, a tobacco (Nicotiana tabacum L. cv. SR1) mRNA that is up-regulated during senescence was isolated by the cDNA-amplified restriction fragment polymorphism method and the cDNA was cloned. The mRNA coded for the early light-induced protein (ELIP), a member of the chlorophyll a/b-binding protein family that has been implicated in assembly or repair of the photosynthetic machinery during early chloroplast development and abiotic stress. A protein antigenically recognized by antibodies to ELIP appeared during senescence with kinetics similar to those of its mRNA. The mRNA, designated ELIP-TOB, was detected earlier when senescence was enhanced by leaf detachment and treatment with 1-amino -cyclopropane-1-carboxylic acid, and was detected later when senescence was retarded by benzyladenine. However, no ELIP-TOB mRNA was seen in the dark even though senescence was accelerated under these conditions. Furthermore, water stress and anaerobiosis stimulated the appearance of ELIP-TOB mRNA before losses of chlorophyll could be detected. We discuss the conditions that may lead to the up-regulation of ELIP-TOB during senescence and speculate as to the role of the gene product in this terminal phase of leaf development.