Growth and physiological response of Yulu <i>Hippophae rhamnoides</i> to drought stress and its omics analysis

<i>Hippophae rhamnoides (H. rhamnoides</i>) is the primary tree species known for its ecological and economic benefits in arid and semi-arid regions. Understanding the response of <i>H. rhamnoides</i> roots to drought stress is essential for promoting the development of varieties. One-year-old Yulu <i>H. rhamnoides</i> was utilized as the experimental material, and three water gradients were established: control (CK), moderate (T1) and severe (T2), over a period of 120 days. The phenotypic traits and physiological indies were assessed and analyzed, while the roots were subjected by RNA-Seq transcriptome and Tandem Mass Tags (TMT) proteome analysis. Drought stress significantly reduced the plant height, ground diameter, root biomass and superoxide dismutase activity; however, the main root length increased. In comparison with CK, a total of 5789 and 5594 differential genes, as well as 63 and 1012 differential proteins, were identified in T1 and T2, respectively. The combined analysis of transcriptome and proteome showed that the number of differentially expressed genes (DEGs) and differentially expressed proteins (DEPs) associated with T1, T2 and CK was 28 and 126, respectively, with 7 and 36 genes achieving effective KEGG annotation. In T1 and T2, the differential genes were significantly enriched in the plant hormone signal transduction pathway, but there was no significant enrichment in the protein expression profile. In T2, 38 plant hormone signal transduction function genes and 10 peroxisome related genes were identified. With the increase of drought stress, the combined expression of DEGs and DEPs increased. Yulu <i>H. rhamnoides</i> may allocate more resources toward CAT while simultaneously decreasing SOD and POD to mitigate the oxidative stress induced by drought. Furthermore, the molecular mechanisms underlying plant hormone signal transduction and peroxisome-related genes in the roots of <i>H. rhamnoides</i> were discussed in greater detail.

沙棘（Hippophae rhamnoides，简称H. rhamnoides）是干旱半干旱地区兼具生态与经济价值的核心树种。解析沙棘根系对干旱胁迫的响应机制，对其品种培育研发具有重要意义。本研究以1年生玉露沙棘为实验材料，设置对照组（CK）、中度干旱组（T1）与重度干旱组（T2）三个水分梯度，处理周期为120天。期间对植株的表型性状与生理指标进行测定分析，并对根系开展RNA测序（RNA-Seq）转录组与串联质量标签（Tandem Mass Tags, TMT）蛋白质组学分析。结果显示，干旱胁迫显著降低了植株株高、地径、根系生物量以及超氧化物歧化酶（SOD）活性，但主根长度有所提升。相较于CK组，T1与T2组分别鉴定得到5789个和5594个差异基因，以及63个和1012个差异蛋白。转录组与蛋白质组联合分析表明，T1、T2与CK间的差异表达基因（differentially expressed genes, DEGs）与差异表达蛋白（differentially expressed proteins, DEPs）的数量分别为28和126，其中7个与36个基因获得了有效的KEGG注释。在T1与T2组中，差异基因显著富集于植物激素信号转导通路，但蛋白质表达谱未出现显著富集现象。在T2组中，共鉴定到38个植物激素信号转导功能基因与10个过氧化物酶体相关基因。随着干旱胁迫程度加剧，差异表达基因与差异表达蛋白的联合表达水平呈上升趋势。玉露沙棘可能会将更多资源分配给过氧化氢酶（CAT），同时下调超氧化物歧化酶（SOD）与过氧化物酶（POD）的表达，以缓解干旱诱导的氧化胁迫。此外，本研究还深入探讨了沙棘根系中植物激素信号转导及过氧化物酶体相关基因所介导的分子调控机制。