DataSheet_2_Combined analyses of transcriptome and metabolome reveal the mechanism of exogenous strigolactone regulating the response of elephant grass to drought stress.xlsx

Elephant grass is widely used in feed production and ecological restoration because of its huge biomass and low occurrence of diseases and insect pets. However, drought seriously affects growth and development of this grass. Strigolactone (SL), a small molecular phytohormone, reportedly participates in improving resilience to cope with arid environment. But the mechanism of SL regulating elephant grass to response to drought stress remains unknown and needs further investigation. We conducted RNA-seq experiments and identified 84,296 genes including 765 and 2325 upregulated differential expression genes (DEGs) and 622 and 1826 downregulated DEGs, compared drought rehydration with spraying SL in roots and leaves, respectively. Combined with targeted phytohormones metabolite analysis, five hormones including 6-BA, ABA, MeSA, NAA, and JA had significant changes under re-watering and spraying SL stages. Moreover, a total of 17 co-expression modules were identified, of which eight modules had the most significant correlation with all physiological indicators with weighted gene co-expression network analysis. The venn analysis revealed the common genes between Kyoto Encyclopedia of Genes and Genomes enriched functional DEGs and the top 30 hub genes of higher weights in eight modules, respectively. Finally, 44 DEGs had been identified as key genes which played a major role in SL response to drought stress. After verification of its expression level by qPCR, six key genes in elephant grass including PpPEPCK, PpRuBPC, PpPGK, PpGAPDH, PpFBA, and PpSBPase genes regulated photosynthetic capacity under the SL treatment to respond to drought stress. Meanwhile, PpACAT, PpMFP2, PpAGT2, PpIVD, PpMCCA, and PpMCCB regulated root development and phytohormone crosstalk to respond to water deficit conditions. Our research led to a more comprehensive understanding about exogenous SL that plays a role in elephant grass response to drought stress and revealed insights into the SL regulating molecular mechanism in plants to adapt to the arid environment.

象草（Elephant grass）因生物量庞大、病虫害发生率极低，被广泛应用于饲料生产与生态修复领域。然而，干旱会严重抑制该牧草的生长发育。独脚金内酯（Strigolactone, SL）作为一种小分子植物激素，据报道可参与增强植物应对干旱环境的抗逆能力。但SL调控象草响应干旱胁迫的分子机制仍未明确，有待进一步探究。本研究开展了RNA测序（RNA-seq）实验，共鉴定得到84296个基因；分别以根部与叶片为研究对象，对比干旱复水处理与SL喷施处理，分别筛选出765、2325个上调差异表达基因（differential expression genes, DEGs），以及622、1826个下调差异表达基因。结合靶向植物激素代谢组分析，结果显示在复水与SL喷施阶段，6-BA、ABA、MeSA、NAA、JA这5种激素均出现显著变化。此外，通过加权基因共表达网络分析（weighted gene co-expression network analysis, WGCNA），本研究共鉴定得到17个共表达模块，其中8个模块与所有生理指标呈现极显著相关性。通过韦恩分析（venn analysis），分别获取了京都基因与基因组百科全书（Kyoto Encyclopedia of Genes and Genomes, KEGG）富集的功能差异表达基因，与8个模块中权重排名前30的核心基因（hub genes）之间的共有基因。最终，共筛选得到44个关键差异表达基因，它们在象草响应干旱胁迫的SL调控通路中发挥核心作用。经实时荧光定量PCR（qPCR）验证其表达水平后发现，象草中的PpPEPCK、PpRuBPC、PpPGK、PpGAPDH、PpFBA及PpSBPase这6个关键基因，可通过调控SL处理下的光合能力以响应干旱胁迫；同时，PpACAT、PpMFP2、PpAGT2、PpIVD、PpMCCA及PpMCCB这6个关键基因，则可通过调控根系发育与植物激素交叉串扰，以响应水分亏缺条件。本研究使我们对外源SL在象草响应干旱胁迫中的作用有了更为全面的认知，并为解析植物通过SL调控通路适应干旱环境的分子机制提供了全新的研究视角。