Abscisic acid biosynthesis in Cercospora rosicola: Sensitivity to inhibitors of sterol biosynthesis.

Norman, Shirley M.; Poling, Stephen M.; Maier, V. P.; Pon, Darryl L.

doi:10.1271/bbb1961.52.1309

Cited by 7 publications

(4 citation statements)

References 2 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Comparison of the effects of many inhibitors of ABA biosynthesis tested in our laboratory (Al-Nimri and Coolbaugh, 1990) as well as those tested by Norman et al (1983Norman et al ( ,1986Norman et al ( ,1988 suggests that triarimol is the most effective inhibitor of ABA biosynthesis reported to date.…”

Section: Discussionmentioning

confidence: 86%

“…The EDgg of ancymidol and triarimol in C. rosicola liquid cultures were 5 x 10"^ and 10"^ M, respectively. Norman et al (1988) studied the effect of many sterol inhibitors on the ABA biosynthetic pathway and found that 10'^ M fenarimol, a triarimol analog, caused 92% inhibition of ABA production. An EDgQ of fenarimol was found to be approximately 5 x 10'^ M.…”

Section: Discussionmentioning

confidence: 99%

“…Norman et al (1986) also found that ancymidol and paclobutrazol inhibited ABA production in C. rosicola. Testing the effects of fenarimol, a close triarimol analog, and several sterol inhibitors on the ABA biosynthetic pathway in C. rosicola led Norman et al (1988) to conclude that a mixed function oxidase is probably involved in one or more steps of the pathway. These data, taken together with those presented here, suggest that triarimol's site of action is on one or more of the oxidative reactions prior to 1'deoxy-ABA, and that the last step in ABA biosynthetic pathway, the hydroxylation of I'-deoxy-ABA into ABA, may not be a Cyt P-450 catalyzed reaction, as it is not inhibited significantly by triarimol.…”

Section: Discussionmentioning

confidence: 99%

“…Ancymidol and some cytokinins also inhibit gibberellin biosynthesis in cell-free preparations from wild cucumber liquid endosperm and other similar systems (Coolbaugh et al, 1982a;Coolbaugh, 1984). Norman et al (1986Norman et al ( ,1988 compared the effects of ancymidol, paclobutrazol, and fenarimol on ABA biosynthesis in C. rosicola. Fenarimol, which is a close analog of triarimol, was shown to have an ED^q (concentration at which ABA accumulation was inhibited by 50%; ED = effective dose) of approximately 5 X 10"^ M. Triarimol was tested for its effects on ABA accumulation in growing cultures of C. rosicola.…”

Section: The Direct Biosynthetic Pathwaymentioning

confidence: 99%

See 3 more Smart Citations

Abscisic acid biosynthesis in Cercospora rosicola and related fungi

Al-Nimri

View full text Add to dashboard Cite

Abscisic acid (ABA) is an important plant hormone involved in controlling normal growth and development in higher plants. The fungus Cercospora rosicola synthesizes large quantities of ABA (Assante et al., 1977), which has made it a useful organism for studies of ABA biosynthesis. The purpose of this study is to examine the ABA biosynthetic pathway in C. rosicola. Feeding experiments with labeled mevalonic acid (MVA), farnesyl pyrophosphate (FPP), and I'-deoxy-ABA have confirmed the conversion of these intermediates into ABA. This conversion was inhibited in the fungicide triarimoltreated cultures fed with MVA and FPP, but not I'-deoxy-ABA. The development of a cell-free enzyme system from fungal extracts capable of converting any of these intermediates into ABA has not been previously reported. A cell-free enzyme system has been developed in our laboratory to convert 1'deoxy-^H-ABA into ^H-ABA. The reaction products were chromatographed by reverse phase HPLC. Tlie presumptive ABA fractions were collected and ^H-ABA was quantified by GC-MS using a ^H-ABA standard curve. I'-deoxy-^H-ABA was converted to an average of 1.47 pmol ^H-ABA mg"^ protein min"^. Most of the enzymatic activity was found in the microsomal fraction. The reaction required NADPH and was enhanced by FAD; it was not inhibited by triarimol. These data, taken together, suggest that cytochrome P-450 may be involved in some oxidative reactions prior to I'-deo^-ABA in the ABA biosynthetic pathway. The phytopathogenic fungi Gnomonia veneta and Cercospora mori infect sycamore and mulberry leaves, respectively. These fungi do not appear to produce ABA in liquid cultures. However, infected leaves with these fungi contain elevated levels of ABA and abscise prematurely.

show abstract