Southern Plains Agricultural Research Center, Agricultural Research Service, US Department of Agriculture, College Station, Texas 77845, United States.
J Agric Food Chem. 2011 May 25;59(10):5351-6. doi: 10.1021/jf200628r. Epub 2011 Apr 27.
Fusarium oxysporum is a fungal pathogen that attacks many important plants. Uniquely pathogenic strains of F. oxysporum f. sp. vasinfectum were inadvertently imported into the United States on live cottonseed for dairy cattle feed. These strains produce exceptionally high concentrations of the phytotoxin fusaric acid. Thus, fusaric acid may be a critical component in the pathogenicity of these biotypes. This study investigated the biosynthesis of fusaric acid using (13)C-labeled substrates including [1,2-(13)C(2)]acetate as well as (13)C- and (15)N-labeled aspartate and [(15)N]glutamine. The incorporation of labeled substrates is consistent with the biosynthesis of fusaric acid from three acetate units at C5-C6, C7-C8, and C9-C10, with the remaining carbons being derived from aspartate via oxaloacetate and the TCA cycle; the oxaloacetate originates in part by transamination of aspartate, but most of the oxaloacetate is derived by deamination of aspartate to fumarate by aspartase. The nitrogen from glutamine is more readily incorporated into fusaric acid than that from aspartate.
尖孢镰刀菌是一种攻击许多重要植物的真菌病原体。独特的致病菌株尖孢镰刀菌 f. sp. vasinfectum 无意中被进口到美国，用于奶牛的活体棉籽饲料。这些菌株产生极高浓度的植物毒素镰刀菌酸。因此，镰刀菌酸可能是这些生物型致病的关键成分。本研究使用 (13)C 标记的底物（包括 [1,2-(13)C(2)] 乙酸盐）以及 (13)C 和 (15)N 标记的天冬氨酸和 [(15)N] 谷氨酰胺来研究镰刀菌酸的生物合成。标记底物的掺入与从 C5-C6、C7-C8 和 C9-C10 的三个乙酸单元合成镰刀菌酸一致，其余的碳通过草酰乙酸和 TCA 循环来自天冬氨酸；草酰乙酸部分来源于天冬氨酸的转氨基作用，但大部分草酰乙酸是由天冬氨酸通过天冬氨酸酶脱氨作用生成富马酸产生的。谷氨酰胺中的氮比天冬氨酸更容易掺入到镰刀菌酸中。
