fusicoccin and ethylene

The phytohormone ethylene is involved in many physiological and developmental processes of plants, as well as in stress responses and in the development of disease resistance. Fusicoccin (FC) is a well-known phytotoxin, that in sycamore (Acer pseudoplatanus L.) cultured cells, induces a set of stress responses, including synthesis of ethylene. In this study, we investigated the possible involvement of ethylene in the FC-induced stress responses of sycamore cells by means of Co(2+), a well-known specific inhibitor of ethylene biosynthesis. Co(2+) inhibited the accumulation of dead cells in the culture, the production of nitric oxide (NO) and of the molecular chaperone Binding Protein (BiP) in the endoplasmic reticulum induced by FC. By contrast, Co(2+) was ineffective on the FC-induced accumulation of cells with fragmented DNA, production of H(2)O(2) and release of cytochrome c from the mitochondrion, and only partially reduced the accumulation of regulative 14-3-3 proteins in the cytosol. In addition, we compared the effect of FC on the above parameters with that of the ethylene-releasing compound ethephon (2-chloroethane phosphonic acid). The results suggest that ethylene is involved in several stress responses induced by FC in sycamore cells, including a form of cell death that does not show apoptotic features and possibly involves NO as a signaling molecule.

Topics: 14-3-3 Proteins; Acer; Cell Death; Cell Nucleus; Cells, Cultured; Cobalt; Culture Media; Cytochromes c; Cytosol; DNA Fragmentation; Ethylenes; Glycosides; Hydrogen Peroxide; Mitochondria; Nitric Oxide; Organophosphorus Compounds; Plant Proteins; Stress, Physiological

Endogenous embryo factors, which act mainly in the radicle, prevent germination in Tagetes minuta at high temperatures. These factors act to prevent cell elongation, which is critical for radicle protrusion under optimal conditions. Once the radicle has emerged both cell elongation and cell division are required for post-germination growth. Germination can be induced at high temperatures by fusicoccin, which rapidly stimulates cell elongation. In addition, priming seeds at 25 degrees C on polyethylene glycol (PEG) 6000 and mannitol could also induce germination on water at 36 degrees C, indicating that priming prevents radicle protrusion at a point subsequent to the point of control in thermoinhibited achenes. Flow cytometry studies revealed that DNA synthesis occurs during thermoinhibition and the inhibition of DNA synthesis during this process inhibits subsequent germination on water under optimal conditions, suggesting a protective role for DNA synthesis in thermoinhibited achenes of T. minuta.

Topics: Cell Division; Cell Nucleus; Cell Size; DNA, Plant; Ethylenes; Germination; Glycosides; Plant Roots; Proton-Translocating ATPases; Pyridones; Seeds; Tagetes; Temperature

The ability of several auxins to induce C2H4 production was examined. There is an ability scale among the various products in which IAA is the more efficient compound while 2,4-D seems to be the less efficient one. As well as other general phenomena, e.g. enlargement or weight increase, even in this case a biphasic action seems to exist, with an activation at the lower concentrations and an inhibition at the higher ones. The dose corresponding to the critical point, in which one can observe the inversion of the response, seems to be common to all the substances and to be 1 X 10(-4)M. Subsequently we verified the FC influence on the C2H4 production in the presence of the optimal dose of different auxins. The inhibiting action exerted by the toxine is a function of the concentration and does not depend on the inducing substance. The FC determines a drastic reduction in C2H4 production, nearly 60%, for the entire range of the concentrations studied. The described data give evidence of a strong FC interference on ethilene production of etiolated pea internodes.

Topics: 2,4-Dichlorophenoxyacetic Acid; Ethylenes; Glycosides; Indoleacetic Acids; Naphthaleneacetic Acids; Plants; Thiazoles