Data from: Transcriptional variation associated with cactus host plant adaptation in Drosophila mettleri

Although the importance of host plant chemistry in plant–insect interactions is widely accepted, the genetic basis of adaptation to host plants is not well understood. Here, we investigate transcriptional changes associated with a host plant shift in Drosophila mettleri. While D. mettleri is distributed mainly throughout the Sonoran Desert where it specializes on columnar cacti (Carnegiea gigantea and Pachycereus pringleii), a population on Santa Catalina Island has shifted to chemically divergent coastal prickly pear cactus (Opuntia littoralis). We compared gene expression of larvae from the Sonoran Desert and Santa Catalina Island when reared on saguaro (C. gigantea), coastal prickly pear and laboratory food. Consistent with expectations based on the complexity and toxicity of cactus relative to laboratory food, within-population comparisons between larvae reared on these food sources revealed transcriptional differences in detoxification and other metabolic pathways. The majority of transcriptional differences between populations on the cactus hosts were independent of the rearing environment and included a disproportionate number of genes involved in processes relevant to host plant adaptation (e.g. detoxification, central metabolism and chemosensory pathways). Comparisons of transcriptional reaction norms between the two populations revealed extensive shared plasticity that likely allowed colonization of coastal prickly pear on Santa Catalina Island. We also found that while plasticity may have facilitated subsequent adaptive divergence in gene expression between populations, the majority of genes that differed in expression on the novel host were not transcriptionally plastic in the presumed ancestral state.

尽管宿主植物化学物质在植物-昆虫互作中的重要性已得到广泛认可，但学界对昆虫适应宿主植物的遗传基础仍知之甚少。本研究以梅特勒果蝇（Drosophila mettleri）为研究对象，探究其在宿主植物转换过程中的转录表达变化。梅特勒果蝇主要分布于索诺兰沙漠，该区域种群特化寄生于柱状仙人掌（包括巨人柱仙人掌Carnegiea gigantea与Pachycereus pringleii）；而圣卡塔利娜岛的种群已转向取食化学组成迥异的沿海梨果仙人掌（Opuntia littoralis）。本研究比较了索诺兰沙漠种群与圣卡塔利娜岛种群的幼虫，在分别取食巨人柱仙人掌、沿海梨果仙人掌以及实验室饲料时的基因表达水平。相较于实验室饲料，仙人掌成分复杂且具有毒性，据此预期，同一种群内取食不同食物来源的幼虫间存在转录表达差异，且这些差异涉及解毒代谢及其他代谢通路，本研究结果与此预期相符。两个仙人掌寄主种群间的绝大多数转录表达差异不受饲养环境影响，且其中显著富集了与宿主植物适应相关的基因（如解毒代谢、中心代谢以及化学感应通路相关基因）。对两个种群的转录反应规范进行比较后发现，二者存在广泛的共享可塑性，这可能助力圣卡塔利娜岛种群成功定殖沿海梨果仙人掌。本研究同时发现，尽管可塑性可能推动了后续种群间基因表达的适应性分化，但在新型寄主上表达存在差异的绝大多数基因，在推测的祖先种群状态下并未表现出转录可塑性。