Donze-Reiner Teresa, Palmer Nathan A, Scully Erin D, Prochaska Travis J, Koch Kyle G, Heng-Moss Tiffany, Bradshaw Jeffrey D, Twigg Paul, Amundsen Keenan, Sattler Scott E, Sarath Gautam
Department of Biology, West Chester University of Pennsylvania, West Chester, PA, 19383, USA.
Wheat, Sorghum, and Forage Research Unit, USDA-ARS, 251 Filley Hall, East Campus, UNL, Lincoln, NE, 68583-0937, USA.
BMC Plant Biol. 2017 Feb 16;17(1):46. doi: 10.1186/s12870-017-0998-2.
Aphid infestation of switchgrass (Panicum virgatum) has the potential to reduce yields and biomass quality. Although switchgrass-greenbug (Schizaphis graminum; GB) interactions have been studied at the whole plant level, little information is available on plant defense responses at the molecular level.
The global transcriptomic response of switchgrass cv Summer to GB was monitored by RNA-Seq in infested and control (uninfested) plants harvested at 5, 10, and 15 days after infestation (DAI). Differentially expressed genes (DEGs) in infested plants were analyzed relative to control uninfested plants at each time point. DEGs in GB-infested plants induced by 5-DAI included an upregulation of reactive burst oxidases and several cell wall receptors. Expression changes in genes linked to redox metabolism, cell wall structure, and hormone biosynthesis were also observed by 5-DAI. At 10-DAI, network analysis indicated a massive upregulation of defense-associated genes, including NAC, WRKY, and MYB classes of transcription factors and potential ancillary signaling molecules such as leucine aminopeptidases. Molecular evidence for loss of chloroplastic functions was also detected at this time point. Supporting these molecular changes, chlorophyll content was significantly decreased, and ROS levels were elevated in infested plants 10-DAI. Total peroxidase and laccase activities were elevated in infested plants at 10-DAI relative to control uninfested plants. The net result appeared to be a broad scale defensive response that led to an apparent reduction in C and N assimilation and a potential redirection of nutrients away from GB and towards the production of defensive compounds, such as pipecolic acid, chlorogenic acid, and trehalose by 10-DAI. By 15-DAI, evidence of recovery in primary metabolism was noted based on transcript abundances for genes associated with carbon, nitrogen, and nutrient assimilation.
Extensive remodeling of the plant transcriptome and the production of ROS and several defensive metabolites in an upland switchgrass cultivar were observed in response to GB feeding. The early loss and apparent recovery in primary metabolism by 15-DAI would suggest that these transcriptional changes in later stages of GB infestation could underlie the recovery response categorized for this switchgrass cultivar. These results can be exploited to develop switchgrass lines with more durable resistance to GB and potentially other aphids.
蚜虫侵害柳枝稷（Panicum virgatum）有可能降低产量和生物质质量。尽管已在整株植物水平上研究了柳枝稷 - 麦二叉蚜（Schizaphis graminum；GB）的相互作用，但关于分子水平上的植物防御反应的信息却很少。
通过RNA测序监测了柳枝稷品种Summer在侵染后5、10和15天收获的受侵染和对照（未受侵染）植株中对GB的全局转录组反应。在每个时间点，将受侵染植株中的差异表达基因（DEG）与未受侵染的对照植株进行分析。5天侵染诱导的GB侵染植株中的DEG包括活性爆发氧化酶和几种细胞壁受体的上调。到5天侵染时，还观察到与氧化还原代谢、细胞壁结构和激素生物合成相关基因的表达变化。在10天侵染时，网络分析表明与防御相关的基因大量上调，包括NAC、WRKY和MYB类转录因子以及潜在的辅助信号分子如亮氨酸氨肽酶。此时也检测到叶绿体功能丧失的分子证据。支持这些分子变化的是，10天侵染时受侵染植株中的叶绿素含量显著降低，ROS水平升高。相对于未受侵染的对照植株，10天侵染时受侵染植株中的总过氧化物酶和漆酶活性升高。最终结果似乎是一种广泛的防御反应，导致碳和氮同化明显减少，并且到10天侵染时营养物质可能从GB重新导向防御化合物如哌啶酸、绿原酸和海藻糖的产生。到15天侵染时，基于与碳、氮和营养同化相关基因的转录丰度，注意到初级代谢恢复的证据。
观察到高地柳枝稷品种中植物转录组的广泛重塑以及ROS和几种防御性代谢物的产生以响应GB取食。到15天侵染时初级代谢的早期丧失和明显恢复表明，GB侵染后期的这些转录变化可能是该柳枝稷品种恢复反应的基础。这些结果可用于培育对GB以及潜在的其他蚜虫具有更强抗性的柳枝稷品系。
