Max Planck Institute for Chemical Ecology, Jena, Germany.
PLoS One. 2010 Jan 15;5(1):e8735. doi: 10.1371/journal.pone.0008735.
Herbivore feeding elicits dramatic increases in defenses, most of which require jasmonate (JA) signaling, and against which specialist herbivores are thought to be better adapted than generalist herbivores. Unbiased transcriptional analyses of how neonate larvae cope with these induced plant defenses are lacking.
METHODOLOGY/PRINCIPAL FINDINGS: We created cDNA microarrays for Manduca sexta and Heliothis virescens separately, by spotting normalized midgut-specific cDNA libraries created from larvae that fed for 24 hours on MeJA-elicited wild-type (WT) Nicotiana attenuata plants. These microarrays were hybridized with labeled probes from neonates that fed for 24 hours on WT and isogenic plants progressively silenced in JA-mediated defenses (N: nicotine; N/PI: N and trypsin protease inhibitors; JA: all JA-mediated defenses). H. virescens neonates regulated 16 times more genes than did M. sexta neonates when they fed on plants silenced in JA-mediated defenses, and for both species, the greater the number of defenses silenced in the host plant (JA > N/PI > N), the greater were the number of transcripts regulated in the larvae. M. sexta larvae tended to down-regulate while H. virescens larvae up- and down-regulated transcripts from the same functional categories of genes. M. sexta larvae regulated transcripts in a diet-specific manner, while H. virescens larvae regulated a similar suite of transcripts across all diet types.
CONCLUSIONS/SIGNIFICANCE: The observations are consistent with the expectation that specialists are better adapted than generalist herbivores to the defense responses elicited in their host plants by their feeding. While M. sexta larvae appear to be better adapted to N. attenuata's defenses, some of the elicited responses remain effective defenses against both herbivore species. The regulated genes provide novel insights into larval adaptations to N. attenuata's induced defenses, and represent potential targets for plant-mediated RNAi to falsify hypotheses about the process of adaptation.
食草动物的进食会引发防御反应的显著增加，其中大多数防御反应需要茉莉酸（JA）信号，而专门的食草动物被认为比一般性食草动物更能适应这些防御反应。缺乏对新孵化幼虫如何应对这些诱导植物防御的无偏转录分析。
方法/主要发现：我们分别为曼陀罗和烟夜蛾创建了 cDNA 微阵列，方法是将从幼虫喂食 24 小时的 MeJA 诱导的野生型（WT）烟草上的中肠特异性 cDNA 文库进行归一化，然后将其点样到微阵列上。这些微阵列与来自新孵化幼虫的标记探针杂交，幼虫喂食 24 小时的 WT 和逐渐沉默 JA 介导的防御的同基因植物（N：尼古丁；N/PI：N 和胰蛋白酶蛋白酶抑制剂；JA：所有 JA 介导的防御）。与在 JA 介导的防御中沉默的宿主植物上进食的 M. sexta 幼虫相比，H. virescens 幼虫调节的基因多 16 倍，对于这两个物种，宿主植物中沉默的防御越多（JA>N/PI>N），幼虫中调节的转录本数量就越多。M. sexta 幼虫往往下调，而 H. virescens 幼虫则上调和下调来自相同功能基因类别的转录本。M. sexta 幼虫以饮食特异性的方式调节转录本，而 H. virescens 幼虫则在所有饮食类型中调节类似的转录本。
结论/意义：这些观察结果与预期一致，即专门的食草动物比一般性食草动物更能适应其进食引起的宿主植物的防御反应。虽然 M. sexta 幼虫似乎更适应 N. attenuata 的防御，但一些诱导的反应仍然是针对这两种食草动物的有效防御。调节的基因提供了幼虫对 N. attenuata 诱导防御的适应的新见解，并代表了植物介导的 RNAi 的潜在靶点，以验证关于适应过程的假设。
