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通过基因回复和突变体互补使玉米赤霉Tri5缺失突变体恢复野生型毒力。

Restoration of wild-type virulence to Tri5 disruption mutants of Gibberella zeae via gene reversion and mutant complementation.

作者信息

Proctor Robert H, Hohn Thomas M, McCormick Susan P

机构信息

Bioactive Agents Unit, National Center for Agricultural Utilization Research, United States Department of Agriculture, Agricultural Research Service, Peoria, IL 61604, USA.

Mycotoxin Research Unit, National Center for Agricultural Utilization Research, United States Department of Agriculture, Agricultural Research Service, Peoria, IL 61604, USA.

出版信息

Microbiology (Reading). 1997 Aug;143 ( Pt 8):2583-2591. doi: 10.1099/00221287-143-8-2583.

Abstract

Gibberella zeae is a pathogen of small grain crops and produces trichothecene mycotoxins in infected host tissue. The role of trichothecenes in the virulence of G. zeae was previously investigated using trichothecene-non-producing mutants that were generated via transformation-mediated disruption of a gene (Tri5) that encodes the first enzyme in the trichothecene biosynthetic pathway. The mutants were less virulent on some hosts than the wild-type strain from which they were derived. Here, we used two approaches to determine whether the reduced virulence of mutants was due specifically to Tri5 disruption or to non-target effects caused by the transformation process. First, we generated a revertant from a Tri5 disruption mutant by allowing the mutant to pass through the sexual phase of its life cycle. In approximately 2% of the resulting progeny the disrupted Tri5 had reverted to wild-type; however, only one of three revertant progeny also regained the ability to produce trichothecenes. In the second approach, we complemented the Tri5 mutation in a disruption mutant by transforming the mutant with a plasmid carrying a functional copy of Tri5. In all transformants examined, the ability to produce trichothecenes was restored. The restoration of trichothecene production in the revertant progeny and in the complemented mutant was accompanied by restoration of wild-type or near wild-type levels of virulence on wheat seedlings (cultivar Wheaton). The results indicate that the reduced virulence of the mutants was caused by disruption of Tri5 rather than non-target effects resulting from the transformation process. The results also provide further evidence that trichothecenes contribute to the virulence of plant-pathogenic fungi.

摘要

禾谷镰刀菌是小粒谷物作物的一种病原体,可在受感染的宿主组织中产生单端孢霉烯族毒素。先前利用通过转化介导破坏编码单端孢霉烯族毒素生物合成途径中第一种酶的基因(Tri5)而产生的不产生单端孢霉烯族毒素的突变体,研究了单端孢霉烯族毒素在禾谷镰刀菌毒力中的作用。这些突变体在某些宿主上的毒力低于其来源的野生型菌株。在此,我们采用两种方法来确定突变体毒力降低是具体由于Tri5破坏还是转化过程引起的非靶向效应。首先,我们让一个Tri5破坏突变体经历其生命周期的有性阶段,从而产生了一个回复突变体。在大约2%的后代中,被破坏的Tri5恢复为野生型;然而,三个回复突变体后代中只有一个也重新获得了产生单端孢霉烯族毒素的能力。在第二种方法中,我们用携带Tri5功能拷贝的质粒转化一个破坏突变体,对其中的Tri5突变进行互补。在所检测的所有转化体中,产生单端孢霉烯族毒素的能力都得到了恢复。回复突变体后代和互补突变体中恢复单端孢霉烯族毒素产生的同时,在小麦幼苗(品种惠顿)上的毒力也恢复到了野生型或接近野生型水平。结果表明,突变体毒力降低是由Tri5破坏引起的,而非转化过程产生的非靶向效应。这些结果还进一步证明了单端孢霉烯族毒素有助于植物病原真菌的毒力。

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