RESUMEN
Biotechnological advances in coffee research (in vitro manipulation, multiplication, generation and development of transgenic coffee plants with specific traits like high yield and good quality) have contributed to description of the metabolic pathways involved in the response mechanisms to environmental factors like abiotic stress. Coffea arabica L. plants grow in acidic soils, and therefore aluminium (Al) toxicity is a major negative impact on crop productivity. To understand Al toxicity mechanisms in cells via the Al absorption kinetic, we isolated protoplasts from two C. arabica L. suspension cell lines: Al-sensitive (L2) and Al-tolerant (LAMt). Protoplasts of LAMt line exhibited lower Al absorption levels than protoplasts of the L2 line. Use of two fluorescent tracers (morin and calcofluor white) indicated that Al interacts with internal cell structures, such as the plasma membrane and nucleus, with differences in both cell lines. Al-tolerance in the LAMt is probably associated with the cell wall as well as intracellular structures. These data will help to better understand Al toxicity in C. arabica, and Al toxicity mechanisms in plant cells.
Asunto(s)
Aluminio/metabolismo , Coffea/metabolismo , Protoplastos/metabolismo , Aluminio/análisis , Aluminio/toxicidad , Células Cultivadas , Coffea/citología , Coffea/efectos de los fármacos , Protoplastos/efectos de los fármacosRESUMEN
The primary Al-tolerance mechanism in plants involves exudation and/or accumulation of specific organic acid species, which form non-phytotoxic complexes with Al(3+) under physiological conditions. An evaluation was done of the role of organic acids in the tolerance mechanism of a cell suspension line of coffee Coffea arabica that exhibits Al-tolerance (LAMt) but for which the metabolic tolerance mechanism remains unknown. Significant differences existed in malate dehydrogenase and citrate synthase activities (key enzymes in organic acids metabolism) between protein extracts (day 7 of culture cycle) of the L2 (Al-sensitive) and LAMt (Al-tolerant) cells when cell suspensions were treated with 100 microM AlCl(3). HPLC analysis showed that the suspension cells of both lines exudate malate when incubated in a minimal solution but that exudation was not enhanced by treatment with AlCl(3) (100 microM). This is the first study demonstrating that plant Al-tolerance may be associated with down-regulation of malate dehydrogenase and citrate synthase activities.