Hk. Abbas et al., FUMONISIN-INDUCED AND AAL-TOXIN-INDUCED DISRUPTION OF SPHINGOLIPID METABOLISM WITH ACCUMULATION OF FREE SPHINGOID BASES, Plant physiology, 106(3), 1994, pp. 1085-1093
Fumonisins (FB) and AAL-toxin are sphingoid-like compounds produced by
several species of fungi associated with plant diseases. In animal ce
lls, both fumonisins produced by Fusarium moniliforme and AAL-toxin pr
oduced by Alternaria alternate f. sp. lycopersici inhibit ceramide syn
thesis, an early biochemical event in the animal diseases associated w
ith consumption of F. moniliforme-contaminated corn. In duckweed (Lemn
a pausicostata Heglem. 6746), tomato plants (Lycopersicon esculentum M
ill), and tobacco callus (Nicotiana tabacum cv Wisconsin), pure FB1 or
AAL-toxin caused a marked elevation of phytosphingosine and sphingani
ne, sphingoid bases normally present in low concentrations. The relati
ve increases were quite different in the three plant systems. Nonethel
ess, disruption of sphingolipid metabolism was clearly a common featur
e in plants exposed to FB1 or AAL-toxin. Resistant varieties of tomato
(Asc/Asc) were much less sensitive to toxin-induced increases in free
sphinganine. Because free sphingoid bases are precursors to plant ''c
eramides,'' their accumulation suggests that the primary biochemical l
esion is inhibition of de novo ceramide synthesis and reacylation of f
ree sphingoid bases. Thus, in plants the disease symptoms associated w
ith A. alternate and F. moniliforme infection may be due to disruption
of sphingolipid metabolism.