Zhang Chao, Peng Xi, Guo Xiaofeng, Tang Gaijuan, Sun Fengli, Liu Shudong, Xi Yajun
1College of Agronomy, Northwest A&F University, Yangling, 712100 Shaanxi China.
2State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest A&F University, Yangling, 712100 Shaanxi China.
Biotechnol Biofuels. 2018 Apr 2;11:91. doi: 10.1186/s13068-018-1088-x. eCollection 2018.
Switchgrass ( L.) is a model biofuel plant because of its high biomass, cellulose-richness, easy degradation to ethanol, and the availability of extensive genomic information. However, a little is currently known about the molecular responses of switchgrass plants to dehydration stress, especially multiple dehydration stresses.
Studies on the transcriptional profiles of 35-day-old tissue culture plants revealed 741 dehydration memory genes. Gene Ontology and pathway analysis showed that these genes were enriched in phenylpropanoid biosynthesis, starch and sucrose metabolism, and plant hormone signal transduction. Further analysis of specific pathways combined with physiological data suggested that switchgrass improved its dehydration resistance by changing various aspects of its responses to secondary dehydration stress (D2), including the regulation of abscisic acid (ABA) and jasmonic acid (JA) biosynthesis and signal transduction, the biosynthesis of osmolytes (l-proline, stachyose and trehalose), energy metabolism (i.e., metabolic process relating to photosynthetic systems, glycolysis, and the TCA cycle), and lignin biosynthesis. The transcriptional data and chemical substance assays showed that ABA was significantly accumulated during both primary (D1) and secondary (D2) dehydration stresses, whereas JA accumulated during D1 but became significantly less abundant during D2. This suggests the existence of a complicated signaling network of plant hormones in response to repeated dehydration stresses. A homology analysis focusing on switchgrass, maize, and revealed the conservation and species-specific distribution of dehydration memory genes.
The molecular responses of switchgrass plants to successive dehydration stresses have been systematically characterized, revealing a previously unknown transcriptional memory behavior. These results provide new insights into the mechanisms of dehydration stress responses in plants. The genes and pathways identified in this study will be useful for the genetic improvement of switchgrass and other crops.
柳枝稷因其生物量高、富含纤维素、易于降解为乙醇以及拥有丰富的基因组信息，是一种典型的生物燃料植物。然而，目前对于柳枝稷植株对脱水胁迫，尤其是多重脱水胁迫的分子反应了解甚少。
对35日龄组织培养植株的转录谱研究发现了741个脱水记忆基因。基因本体论和通路分析表明，这些基因在苯丙烷生物合成、淀粉和蔗糖代谢以及植物激素信号转导中富集。结合生理数据对特定通路的进一步分析表明，柳枝稷通过改变其对二次脱水胁迫（D2）反应的各个方面来提高其脱水抗性，包括脱落酸（ABA）和茉莉酸（JA）生物合成及信号转导的调控、渗透调节物质（L-脯氨酸、水苏糖和海藻糖）的生物合成、能量代谢（即与光合系统、糖酵解和三羧酸循环相关的代谢过程）以及木质素生物合成。转录数据和化学物质分析表明，ABA在初次（D1）和二次（D2）脱水胁迫期间均显著积累，而JA在D1期间积累，但在D2期间显著减少。这表明存在一个复杂的植物激素信号网络以应对反复的脱水胁迫。对柳枝稷、玉米和[此处原文缺失相关内容]的同源性分析揭示了脱水记忆基因的保守性和物种特异性分布。
柳枝稷植株对连续脱水胁迫的分子反应已得到系统表征，揭示了一种此前未知的转录记忆行为。这些结果为植物脱水胁迫反应机制提供了新的见解。本研究中鉴定出的基因和通路将有助于柳枝稷及其他作物的遗传改良。
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