Phlomoides rotata is a traditional Chinese herbal medicine that grows in the Qinghai–Tibet Plateau region at a 3100–5000 m altitude. Iridoid compounds are the main active compounds of the P. rotata used as medical ingredients and display anti-inflammatory, analgesic, and hepatoprotective properties. To better understand the biological mechanisms of iridoid compounds in this species, we performed a comprehensive analysis of the transcriptome and metabolome of P. rotata leaves from four different regions (3540–4270 m). Global metabolome profiling detected 575 metabolites, and 455 differentially accumulated metabolites (DAMs) were detected in P. rotata leaves from the four regions. Eight major DAMs related to iridoid metabolism in P. rotata leaves were investigated: shanzhiside methyl ester, 8-epideoxyloganic acid, barlerin, shanzhiside, geniposide, agnuside, feretoside, and catalpin. In addition, five soil physical and chemical indicators in P. rotata rhizosphere soils were analyzed. Four significant positive correlations were observed between alkaline nitrogen and geniposide, exchangeable calcium and geniposide, available potassium and shanzhiside, and available phosphorus and shanzhiside methyl ester. The transcriptome data showed 12 P. rotata cDNA libraries with 74.46 Gb of clean data, which formed 29,833 unigenes. Moreover, 78.91% of the unigenes were annotated using the eight public databases. Forty-one candidate genes representing 23 enzymes involved in the biosynthesis of iridoid compounds were identified in P. rotata leaves. Moreover, the DXS1, IDI1, 8-HGO1, and G10H2 genes associated with iridoid biosynthesis were specifically expressed in P. rotata. The integration of transcriptome and metabolome analyses highlights the crucial role of soil physical and chemical indicators and major gene expression related to iridoid metabolism pathways in P. rotata from different areas. Our findings provide a theoretical foundation for exploring the molecular mechanisms underlying iridoid compound accumulation in P. rotata.

Hairgrass (Deschampsia caespitosa), a widely distributed grass species considered promising in the ecological restoration of degraded grassland in the Qinghai-Xizang Plateau, is likely to be subjected to frequent drought and waterlogging stress due to ongoing climate change, further aggravating the degradation of grassland in this region. However, whether it would acclimate to water stresses resulting from extreme climates remains unknown. Proline accumulation is a crucial metabolic response of plants to challenging environmental conditions. This study aims to investigate the changes in proline accumulation and key enzymes in hairgrass shoot and root tissues in response to distinct climate extremes including moderate drought, moderate waterlogging, and dry–wet variations over 28 days using a completely randomized block design. The proline accumulation, contribution of the glutamate and ornithine pathways, and key enzyme activities related to proline metabolism in shoot and root tissues were examined. The results showed that water stress led to proline accumulation in both shoot and root tissues of hairgrass, highlighting the importance of this osmoprotectant in mitigating the effects of environmental challenges. The differential accumulation of proline in shoots compared to roots suggests a strategic allocation of resources by the plant to cope with osmotic stress. Enzymatic activities related to proline metabolism, such as Δ¹-pyrroline-5-carboxylate synthetase, ornithine aminotransferase, Δ¹-pyrroline-5-carboxylate reductase, Δ¹-pyrroline-5-carboxylate dehydrogenase, and proline dehydrogenase, further emphasize the dynamic regulation of proline levels in hairgrass under water stress conditions. These findings support the potential for enhancing the stress resistance of hairgrass through the genetic manipulation of proline biosynthesis and catabolism pathways.

Desertification severely impacts soil environments, necessitating effective control measures to improve sandy soil. On the alpine sandy land of Gonghe Basin, taking bare land containing mobile sand dunes (LD) as a reference, surface soil undergoing four afforestation measures, namely Salix cheilophila + Populus simonii (WLYY), Salix psammophila + Salix cheilophila (SLWL), Artemisia ordosica + Caragana korshinskii (SHNT), and Caragana korshinskii (NT80), was studied, with soil physicochemical properties and enzyme activity measured and the bacterial community structure analyzed using Illumina high-throughput sequencing. Compared to LD, all four afforestation measures significantly reduced the sand content, while increasing soil total carbon, total nitrogen, organic matter, alkali-hydrolyzable nitrogen, and available potassium. WLYY, SLWL, and SHNT significantly increased the surface soil total phosphorus and total potassium. Catalase, sucrase, urease, and alkaline phosphatase activities significantly increased under all four measures. Among them, the highest improvements were observed under SLWL, followed by WLYY. All treatments increased soil bacterial community richness, exhibiting significantly different bacterial community compositions to those in LD. Total phosphorus was the key physicochemical factor affecting the soil bacterial community structure, while enzyme activity was significantly correlated with the relative abundance of most major bacterial phyla. All measures improved the surface soil environment, with SLWL demonstrating the best improvement. The results provide valuable reference for sand prevention and control strategies in alpine sandy areas and offer a theoretical basis for the ecological restoration of sandy soil microenvironments.