Free proline has multiple functions in plant cells, such as regulating osmotic potential and protecting both proteins and cell membranes. The expression of Δ1-Pyrroline-5-carboxylate synthase (P5CS), a key enzyme in the proline biosynthetic pathway, increases under drought, salt and cold stress conditions, causing plant cells to accumulate large amounts of proline. In this study, we cloned and identified the P5CS gene from Stipa purpurea, which has a full-length of 2196 bp and encodes 731 amino acids. A subcellular localization analysis indicated that SpP5CS localized to the cytoplasm. The ectopic overexpression of SpP5CS in Arabidopsis thaliana resulted in higher proline contents, longer roots, higher survival rates and less membrane damage under drought stress conditions compared with wild-type controls. SpP5CS-overexpressing A. thaliana was more resistant to drought stress than the wild type, whereas the deletion mutant sp5cs was less resistant to drought stress. Thus, SpP5CS may be a potential candidate target gene for increasing plant resistance to drought stress.

(1) Background: Hippophae gyantsensis, a drought-tolerant plant native to the Tibetan Plateau, plays a crucial ecological and economic role. While its drought tolerance mechanisms have been extensively studied, the role of alternative splicing (AS) in drought resistance remains insufficiently explored. This study aims to elucidate how AS events regulate gene expression to enhance drought tolerance in H. gyantsensis under water-deficit conditions. (2) Methods: H. gyantsensis plants were subjected to progressive drought stress followed by rehydration. Physiological responses, transcriptomic data, and hormonal profiles were analyzed to investigate the plant’s adaptive mechanisms to drought stress, with a particular focus on abscisic acid (ABA) signaling-related genes. (3) Results: The results showed that H. gyantsensis maintained high leaf water content even under severe drought stress, emphasizing its strong drought resistance. A transcriptomic analysis revealed 11,962 differentially expressed genes, primarily enriched in hormone signaling and metabolic pathways. Notably, the accumulation of ABA was closely associated with AS events in ABA-related genes, such as ZEPs, ABCG, and PP2C. These genes produced multiple splice variants, indicating their role in modulating the ABA signaling pathway and enhancing drought tolerance. (4) Conclusions: This study highlights the pivotal role of AS in ABA signaling and drought tolerance in H. gyantsensis. It provides new insights into how AS contributes to plant adaptation to drought stress, bridging the knowledge gap in drought resistance mechanisms and emphasizing the importance of AS in plant stress responses.

Hippophae neurocarpa (H. neurocarpa) is a deciduous shrub from the Elaeagnaceae family, widely distributed in the Qinghai-Tibet Plateau. It possesses significant ecological and economic value, while also being rich in nutrients and offering various health benefits. In this study, we successfully assembled the chromosome-level genome of H. neurocarpa utilizing Illumina sequencing, Nanopore sequencing, and chromosome conformation capture techniques. The total genome size is 682.80 Mb, with an N50 length of 62.17 Mb. We successfully anchored 669.20 Mb to 12 chromosomes, achieving a mapping rate of 98.0%. Furthermore, using RepeatMasker, we annotated repetitive sequences, revealing that 56.27% of the genome consists of repetitive elements, with long terminal repeats (LTRs) accounting for 36.26% of the total genome. We also annotated gene structures using de novo, homology, and transcriptome assembly strategies, predicting 36844 protein-coding genes, of which 32952 genes had successful functional annotations. Lastly, we employed various strategies for quality evaluation, with a Benchmarking Universal Single-Copy Orthologs (BUSCO) completeness score reaching 97.6% and a Long Terminal Repeat (LTR) Retrotransposon Assembly Index (LAI) of 11.61, the mapping rate further indicating high assembly quality. This study provides valuable genomic data for future research on H. neurocarpa and the broader sea buckthorn genus.