Mol Plant Microbe Interact. 2013 Dec;26(12):1464-72. doi: 10.1094/MPMI-04-13-0121-R.
Cereals contain xylanase inhibitor (XI) proteins which inhibit microbial xylanases and are considered part of the defense mechanisms to counteract microbial pathogens. Nevertheless, in planta evidence for this role has not been reported yet. Therefore, we produced a number of transgenic plants constitutively overexpressing TAXI-III, a member of the TAXI type XI that is induced by pathogen infection. Results showed that TAXI-III endows the transgenic wheat with new inhibition capacities. We also showed that TAXI-III is correctly secreted into the apoplast and possesses the expected inhibition parameters against microbial xylanases. The new inhibition properties of the transgenic plants correlate with a significant delay of Fusarium head blight disease symptoms caused by Fusarium graminearum but do not significantly influence leaf spot symptoms caused by Bipolaris sorokiniana. We showed that this contrasting result can be due to the different capacity of TAXI-III to inhibit the xylanase activity of these two fungal pathogens. These results provide, for the first time, clear evidence in planta that XI are involved in plant defense against fungal pathogens and show the potential to manipulate TAXI-III accumulation to improve wheat resistance against F. graminearum.
谷物含有木聚糖酶抑制剂（XI）蛋白，它可以抑制微生物木聚糖酶，被认为是抵御微生物病原体的防御机制的一部分。然而，目前还没有关于这种作用的体内证据。因此，我们生产了一些组成型过表达 TAXI-III 的转基因植物，TAXI-III 是一种被病原体感染诱导的 TAXI 型 XI 的成员。结果表明，TAXI-III 赋予了转基因小麦新的抑制能力。我们还表明，TAXI-III 被正确地分泌到质外体中，并具有针对微生物木聚糖酶的预期抑制参数。转基因植物的新抑制特性与由禾谷镰刀菌引起的赤霉病症状的显著延迟相关，但不会显著影响由双极镰刀菌引起的叶斑症状。我们表明，这种对比的结果可能是由于 TAXI-III 对这两种真菌病原体的木聚糖酶活性的抑制能力不同。这些结果首次在体内提供了明确的证据，表明 XI 参与了植物对真菌病原体的防御，并显示了操纵 TAXI-III 积累以提高小麦对禾谷镰刀菌抗性的潜力。
