Iris lactea var. chinensis plant drought tolerance depends on the response of proline metabolism, transcription factors, transporters and the ROS-scavenging system.

BACKGROUND: Iris lactea var. chinensis, a perennial herbaceous species, is widely distributed and has good drought tolerance traits. However, there is little information in public databases concerning this herb, so it is difficult to understand the mechanism underlying its drought tolerance. RESULTS: In this study, we used Illumina sequencing technology to conduct an RNA sequencing (RNA-seq) analysis of I. lactea var. chinensis plants under water-stressed conditions and rehydration to explore the potential mechanisms involved in plant drought tolerance. The resulting de novo assembled transcriptome revealed 126,979 unigenes, of which 44,247 were successfully annotated. Among these, 1187 differentially expressed genes (DEGs) were identified from a comparison of the water-stressed treatment and the control (CK) treatment (T/CK); there were 481 upregulated genes and 706 downregulated genes. Additionally, 275 DEGs were identified in the comparison of the rehydration treatment and the water-stressed treatment (R/T). Based on Quantitative Real-time Polymerase Chain Reaction (qRT-PCR) analysis, the expression levels of eight randomly selected unigenes were consistent with the transcriptomic data under water-stressed and rehydration treatment, as well as in the CK. According to Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, proline metabolism-related DEGs, including those involved in the 'proline catabolic process', the 'proline metabolic process', and 'arginine and proline metabolism', may play important roles in plant drought tolerance. Additionally, these DEGs encoded 43 transcription factors (TFs), 46 transporters, and 22 reactive oxygen species (ROS)-scavenging system-related proteins. Biochemical analysis and histochemical detection showed that proline and ROS were accumulated under water-stressed conditions, which is consistent with the result of the transcriptomic analysis. CONCLUSIONS: In summary, our transcriptomic data revealed that the drought tolerance of I. lactea var. chinensis depends on proline metabolism, the action of TFs and transporters, and a strong ROS-scavenging system. The related genes found in this study could help us understand the mechanisms underlying the drought tolerance of I. lactea var. chinensis.

Single-cell transcriptome profiling reveals the spatiotemporal distribution of triterpenoid saponin biosynthesis and transposable element activity in Gynostemma pentaphyllum shoot apexes and leaves.

Gynostemma pentaphyllum (Thunb.) Makino is an important producer of dammarene-type triterpenoid saponins. These saponins (gypenosides) exhibit diverse pharmacological benefits such as anticancer, antidiabetic, and immunomodulatory effects, and have major potential in the pharmaceutical and health care industries. Here, we employed single-cell RNA sequencing (scRNA-seq) to profile the transcriptomes of more than 50,000 cells derived from G. pentaphyllum shoot apexes and leaves. Following cell clustering and annotation, we identified five major cell types in shoot apexes and four in leaves. Each cell type displayed substantial transcriptomic heterogeneity both within and between tissues. Examining gene expression patterns across various cell types revealed that gypenoside biosynthesis predominantly occurred in mesophyll cells, with heightened activity observed in shoot apexes compared to leaves. Furthermore, we explored the impact of transposable elements (TEs) on G. pentaphyllum transcriptomic landscapes. Our findings the highlighted the unbalanced expression of certain TE families across different cell types in shoot apexes and leaves, marking the first investigation of TE expression at the single-cell level in plants. Additionally, we observed dynamic expression of genes involved in gypenoside biosynthesis and specific TE families during epidermal and vascular cell development. The involvement of TE expression in regulating cell differentiation and gypenoside biosynthesis warrant further exploration. Overall, this study not only provides new insights into the spatiotemporal organization of gypenoside biosynthesis and TE activity in G. pentaphyllum shoot apexes and leaves but also offers valuable cellular and genetic resources for a deeper understanding of developmental and physiological processes at single-cell resolution in this species.

[Effects of Vegetation Restoration on the Structure and Function of the Rhizosphere Soil Bacterial Community of Solanum rostratum].

Invasive plants can change soil microbial communities and therefore promote invasion. While vegetation restoration has been adopted in certain infested lands to curb the invasion of Solanum rostratum, changes in the composition and function of rhizosphere soil bacterial communities of the species before and after the restoration has not yet been reported. In this study, two vegetation combinations used in previous studies were selected as candidates:Astragalus adsurgens+Elymus dahuricus+Bromus inermis (T1) and A. adsurgens+Festuca arundinacea+Agropyron cristatum+Leymus chinensis (T2). Rhizosphere soil samples were collected from each combination (T1 and T2), a S. rostratum invaded area (SR), and the native plant (NP) control to analyze the bacterial community structure and diversity using 16S rDNA gene sequencing on the Illumina MiSeq platform. PICRUSt was further used to predict the functional abilities of soil bacterial communities. Results of 16S rDNA gene sequencing showed that both the Simpson and Chao1 indices were higher in the SR treatment than in the NP treatment, but neither reached a significant level, although both indices decreased significantly after vegetation restoration (T1 and T2; P<0.05). The relative abundance of Microvirga, Skermanella, and Sphingomonas from phylum Proteobacteria and Bryobacter from the phylum Acidobacteria were significantly lower in the SR treatment (P<0.05) when compared with the NP treatment and higher in restoration treatments (T1 and T2). The RDA analysis showed that soil organic matter (OM), total nitrogen (TN), total phosphorus (TP), total potassium (TK), and available potassium (AK) were important factors affecting the composition of the bacterial community. Based on the PICRUSt analysis of soil bacterial community functions, the relative abundance of gene families related to biosynthesis of amino acids, purine metabolism, pyrimidine metabolism, ribosome, and aminoacyl-tRNA biosynthesis were higher in the rhizosphere samples of the SR treatment than those of the NP treatment and reduced significantly after vegetation restoration (T1 and T2; P<0.05). The structure and function of rhizosphere soil bacterial community of S. rostratum and vegetation restoration were analyzed and provided a theoretical basis for the invasion mechanism and ecological restoration of S. rostratum.