Department of Ecology, Environment and Plant Sciences, Stockholm University, Stockholm, Sweden.
Cell and Molecular Science, James Hutton Institute, Invergowrie, Dundee, United Kingdom.
PLoS One. 2018 Mar 19;13(3):e0193816. doi: 10.1371/journal.pone.0193816. eCollection 2018.
Aphids are serious pests in crop plants. In an effort to identify plant genes controlling resistance against aphids, we have here studied a protease inhibitor, CI2c in barley (Hordeum vulgare L.). The CI2c gene was earlier shown to be upregulated by herbivory of the bird cherry-oat aphid (Rhopalosiphum padi L.) in barley genotypes with moderate resistance against this aphid, but not in susceptible lines. We hypothesized that CI2c contributes to the resistance. To test this idea, cDNA encoding CI2c was overexpressed in barley and bioassays were carried out with R. padi. For comparison, tests were carried out with the green peach aphid (Myzus persicae Sulzer), for which barley is a poor host. The performance of R. padi was not different on the CI2c-overexpressing lines in comparison to controls in test monitoring behavior and fecundity. M. persicae preference was affected as shown in the choice test, this species moved away from control plants, but remained on the CI2c-overexpressing lines. R. padi-induced responses related to defense were repressed in the overexpressing lines as compared to in control plants or the moderately resistant genotypes. A putative susceptibility gene, coding for a β-1,3-glucanase was more strongly induced by aphids in one of the CI2c-overexpressing lines. The results indicate that the CI2c inhibitor in overexpressing lines affects aphid-induced responses by suppressing defense. This is of little consequence to the specialist R.padi, but causes lower non-host resistance towards the generalist M. persicae in barley.
蚜虫是农作物的严重害虫。为了鉴定控制抗蚜虫的植物基因，我们研究了大麦（Hordeum vulgare L.）中的一种蛋白酶抑制剂 CI2c。先前的研究表明，该 CI2c 基因在中度抗这种蚜虫的大麦基因型中受到鸟樱桃燕麦蚜虫（Rhopalosiphum padi L.）的取食而上调，但在易感系中没有上调。我们假设 CI2c 有助于抵抗。为了验证这一想法，我们在大麦中过表达了编码 CI2c 的 cDNA，并进行了 R. padi 的生物测定。为了进行比较，还对桃蚜（Myzus persicae Sulzer）进行了测试，桃蚜对大麦是不良宿主。与对照相比，在监测行为和繁殖力的测试中，R. padi 在过表达 CI2c 的系中表现没有差异。选择试验表明，桃蚜的偏好受到影响，这种蚜虫远离对照植物，但仍停留在过表达 CI2c 的系上。与对照植物或中度抗性基因型相比，过表达系中与防御相关的 R. padi 诱导反应受到抑制。一个假定的易感性基因，编码β-1,3-葡聚糖酶，在过表达系中比在对照植物或中度抗性基因型中受蚜虫诱导的程度更强。结果表明，过表达系中的 CI2c 抑制剂通过抑制防御来影响蚜虫诱导的反应。这对专食性的 R. padi 影响不大，但会导致大麦中针对一般性的 M. persicae 的非专化抗性降低。
