Unigene-based RNA-seq provides insights on drought stress responses in Marsdenia tenacissima

Differential Gene Expression and Metabolic Pathway Analysis of Cladophora rupestris under Pb Stress Conditions

This study aimed to analyze the transcriptome of C. rupestris under Pb²⁺ stress by using high-throughput sequencing technology, observe the changes of gene expression and metabolic pathway after three and five days under 1.0 and 5.0 mg/L of Pb²⁺ treatment, and analyze the differentially expressed genes (DEGs) and related functional genes after Pb²⁺ treatment. Metabolic pathways were revealed through Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. Results show that DEGs increased significantly with the increase of Pb²⁺ concentration and stress time. A total of 32 genes were closely related to Pb²⁺ stress response. GO analysis identified two major transporter proteins, namely, ATP-binding transport protein-related (ABC transporters) and zinc finger CCHC domain containing protein (Zfp) in C. rupestris. Pthr19248, pthr19211, Zfp pthr23002, Zfp p48znf pthr12681, Zfp 294 pthr12389, and Zfp pthr23067 played important roles against Pb²⁺ toxicity and its absorption in C. rupestris. KEGG pathway analysis suggested that ABCA1, ATM, and ABCD3 were closely related to Pb²⁺ absorption. Pb²⁺ stress was mainly involved in metallothionein (MT), plant hormone signal transduction, ABC transporters, and glutathione (GSH) metabolism.

Plant adaptability in karst regions

Karst ecosystems are formed by dissolution of soluble rocks, usually with conspicuous landscape features, such as sharp peaks, steep slopes and deep valleys. The plants in karst regions develop special adaptability. Here, we reviewed the research progresses on plant adaptability in karst regions, including drought, high temperature and light, high-calcium stresses responses and the strategies of water utilization for plants, soil nutrients impact, human interference and geographical traits on karst plants. Drought, high temperature and light change their physiological and morphological structures to adapt to karst environments. High-calcium and soil nutrients can transfer surplus nutrients to special parts of plants to avoid damage of high nutrient concentration. Therefore, karst plants can make better use of limited water. Human interference also affects geographical distribution of karst plants and their growing environment. All of these aspects may be analyzed to provide guidance and suggestions for related research on plant adaptability mechanisms.

Gaining Insight into Exclusive and Common Transcriptomic Features Linked to Drought and Salinity Responses across Fruit Tree Crops

The present study aimed at identifying and mapping key genes expressed in root tissues involved in drought and salinity tolerance/resistance conserved among different fruit tree species. Twenty-six RNA-Seq samples were analyzed from six published studies in five plant species (Olea europaea, Vitis riparia Michx, Prunus mahaleb, Prunus persica, Phoenix dactylifera). This meta-analysis used a bioinformatic pipeline identifying 750 genes that were commonly modulated in three salinity studies and 683 genes that were commonly regulated among three drought studies, implying their conserved role in resistance/tolerance/response to these environmental stresses. A comparison was done on the genes that were in common among both salinity and drought resulted in 82 genes, of which 39 were commonly regulated with the same trend of expression (23 were upregulated and 16 were downregulated). Gene set enrichment and pathway analysis pointed out that pathways encoding regulation of defense response, drug transmembrane transport, and metal ion binding are general key molecular responses to these two abiotic stress responses. Furthermore, hormonal molecular crosstalk plays an essential role in the fine-tuning of plant responses to drought and salinity. Drought and salinity induced a different molecular "hormonal fingerprint". Dehydration stress specifically enhanced multiple genes responsive to abscisic acid, gibberellin, brassinosteroids, and the ethylene-activated signaling pathway. Salt stress mostly repressed genes encoding for key enzymes in signaling proteins in auxin-, gibberellin-(gibberellin 2 oxidase 8), and abscisic acid-related pathways (aldehyde oxidase 4, abscisic acid-responsive element-binding protein 3). Abiotic stress-related genes were mapped into the chromosome to identify molecular markers usable for the improvement of these complex quantitative traits. This meta-analysis identified genes that serve as potential targets to develop cultivars with enhanced drought and salinity resistance and/or tolerance across different fruit tree crops in a biotechnological sustainable way.

Transcriptomic response to cold of thermophilous medicinal plant Marsdenia tenacissima

Extracts from Marsdenia tenacissima, involving tenacissoside H, I and G, have been used as remedies of cancer, inflammation and asthma. Low temperature serves as one of the main factors constrain the planting expansion and quality of M. tenacissima, but its functional mechanism has been known scarcely for the lack of genomic information and transcriptional profile. Here we investigated the transcriptomic responses of M. tenacissima under cold stress to gain insight into the molecular mechanism of low temperature sensitivity. Total RNAs were collected from samples obtained at 4-time points (after 0, 3, 6 and 48 h cold treatments with 4 °C, respectively), then used for library construction and sequenced on the Illumina Hiseq™ 4000 platform. Passing quality assessments, 500794 transcripts, and 206137 unigenes were de novo assembly out in Trinity v2.4.0, holding contig N50 of 2566 bp and unigene mean length of 754 bp. 44.20% of assembled unigenes were annotated to the well-known public protein database on a basis of sequence similarity. Using statistical comparison of the fragments per kilo base of transcript per million reads mapped (FPKM) values between conditions, 6082 group-specific differentially expressed genes (DEGs) were identified and considered as cold-responsive genes, which contained copious transcription factors and active secondary metabolism. Among them, 43 unigenes were constantly up-regulated expression along with cold time, which mainly implicated in the biosynthesis of secondary metabolites, carbon metabolism, RNA and DNA metabolism. Conversely, 21 unigenes involved in photosynthesis, cell wall, protein degradation, and transporters were downregulated continually with cold timescale. Experimentally, MtEF1α was chosen as the best housekeeping gene. Functional enrichments found that damaging of cold stress on M. tenacissima may be ascribed to inability of photosynthesis, ribsome processing, flavonoid biosynthesis and terpenoids degradation. Correlation analysis between cold induced transcription factors and tenacissoside biosynthesis-related genes indicated that 3β-HSD significant positively correlated with bHLH51, and 4-MSO with NF-YB, GRAS3, Trihelix, FAR1, MYB60, MYBS1, bZIP43. Further promoter clone found MYB-binding site in the promoter of 4-MSO. In view of the reported cold tolerance of MYB60, it is recommended as a potential candidate suitable for future molecular design of exaptation cultivation with high bioactive constituents.