坏死效应物ToxA是由几种真菌坏死因子产生的经过充分研究的毒力因子。ToxA最初于1996年从小麦棕褐色斑点病原体pyrenophoratritici-repectis中克隆,近十年后在另一种真菌病原体Parastagonosporanodorum及其姐妹物种Parastagonsporapseudonodorum中被发现。2018年,在第三种小麦真菌病原物种中检测到ToxA:导致斑点斑点病的Biparlissorokiniana。然而,与Tritici-Repentis和Nodorum的情况不同,近年来,仅对B.srookiniana中的ToxA进行了研究。在这份报告中,评估了五个澳大利亚B.srookiniana分离株是否存在ToxA。发现四个分离物含有ToxA。虽然一种分离株具有先前报道的ToxA单倍型序列(ToxA19),三个分离株含有不同的单倍型,在本文中指定为ToxA25,其具有导致在位置168处甘氨酸至精氨酸的氨基酸改变的非同义突变。两种索罗基芽孢杆菌ToxA亚型,当在大肠杆菌中异源表达时,在ToxA敏感的Tsn1品种上表现出经典的ToxA坏死诱导活性。对澳大利亚小麦品种上的B.sorokiniana分离株的初步分析表明,具有ToxA19,ToxA25或ToxA缺陷的分离株表现出不同程度的毒力,对那些产生ToxA的人观察到最具侵略性的分离株。观察到Tsn1和tsn1品种之间斑点病严重程度的差异,然而,这并不限于产生ToxA的分离株.总体结果表明,澳大利亚B.srookiniana分离株的毒力是多种多样的,其毒性A-Tsn1相互作用的重要性取决于单个分离株。
The necrotrophic effector ToxA is a well-studied virulence factor produced by several fungal necrotrophs. Initially cloned from the wheat tan spot pathogen Pyrenophora tritici-repentis in 1996, ToxA was found almost a decade later in another fungal pathogen, Parastagonospora nodorum, and its sister species, Parastagonospora pseudonodorum. In 2018, ToxA was detected in a third wheat fungal pathogenic species,
Bipolaris sorokiniana, which causes spot blotch disease. However, unlike the case with P. tritici-repentis and P. nodorum, the ToxA in B. sorokiniana has only been investigated in recent years. In this report, five Australian B. sorokiniana isolates were assessed for the presence of ToxA. Four isolates were found to contain ToxA. While one isolate harbored the previously reported ToxA haplotype sequence (ToxA19), three isolates contain a different haplotype, designated herein as ToxA25, which has a nonsynonymous mutation resulting in an amino acid change of glycine to arginine at position 168. Both B. sorokiniana ToxA isoforms, when heterologously expressed in Escherichia coli, exhibited the classic ToxA necrosis-inducing activity on ToxA-sensitive Tsn1 cultivars. Preliminary analysis of the B. sorokiniana isolates in Australian wheat cultivars showed that isolates with ToxA19, ToxA25, or ToxA-deficient displayed various degrees of virulence, with the most aggressive isolates observed for those producing ToxA. Differences in spot blotch disease severity between Tsn1 and tsn1 cultivars were observed; however, this was not limited to the ToxA-producing isolates. The overall results suggest that the virulence of the Australian B. sorokiniana isolates is diverse, with the significance of ToxA-Tsn1 interactions depending on individual isolates.