Background: Melatonin, a multifunctional signal molecule, has been reported to play crucial roles in growth and development and stress responses in various plant species. Okra (Abelmoschus esculentus L.) is a food crop with extremely high values of nutrition and healthcare. Recent reports have revealed the protective role of melatonin in alleviating salt stress. However, little is known about its regulatory mechanisms in response to salt stress in okra. Results: In this study, we explored whether exogenous melatonin pretreatment could alleviate salt stress (300 mM NaCl) of okra plants. Results showed that exogenous application of melatonin (50 μM) significantly enhanced plant tolerance to salt stress, as demonstrated by the plant resistant phenotype, as well as by the higher levels of the net photosynthetic rate, chlorophyll fluorescence and chlorophyll content in comparison with nontreated salt-stressed plants. Additionally, melatonin pretreatment remarkably decreased the levels of lipid peroxidation and H₂O₂ content and scavenged O₂^•- in melatonin-pretreated plants, which may be attributed to the higher levels of enzyme activities including POD and GR. Moreover, a combination of third- (PacBio) and second-generation (Illumina) sequencing technologies was applied to sequence full-length transcriptomes of okra. A total of 121,360 unigenes was obtained, and the size of transcript lengths ranged from 500 to 6000 bp. Illumina RNA-seq analysis showed that: Comparing with control, 1776, 1063 and 1074 differential expression genes (DEGs) were identified from the three treatments (NaCl, MT50 and MT + NaCl, respectively). These genes were enriched in more than 10 GO terms and 34 KEGG pathways. Nitrogen metabolism, sulfur metabolism, and alanine, aspartate and glutamate metabolism were significantly enriched in all three treatments. Many transcription factors including MYB, WRKY, NAC etc., were also identified as DEGs. Conclusions: Our preliminary results suggested that melatonin pretreatment enhanced salt tolerance of okra plants for the first time. These data provide the first set of full-length isoforms in okra and more comprehensive insights into the molecular mechanism of melatonin responses to salt stress.

Salinization seriously threatens land use efficiency and crop yields across the world. Understanding the mechanisms plants use to protect against salt stress will help breeders develop salt-tolerant vegetable crops. Okra (Abelmoschus esculentus L.) is an important vegetable crop of the mallow family, which is now cultivated in warm regions worldwide. To understand the effects of salt stress on the protein level of okra, a comparative proteomic analysis of okra seedlings grown in the presence of 0 or 300 mmol L− 1 NaCl treatment was performed using an integrated approach of Tandem Mass Tag labeling and LC-MS/MS integrated approach. A total of 7179 proteins were identified in this study, for which quantitative information was available for 5774 proteins. In the NaCl/control comparison group, there were 317 differentially expressed proteins (DEPs), of which 165 proteins were upregulated and 152 proteins downregulated in the presence of NaCl. Based on the above data, we carried out a systematic bioinformatics analysis of proteins with information, including protein annotation, domain characteristics, functional classification, and pathway enrichment. Enriched gene ontology and Kyoto Encyclopedia of Genes and Genomes pathway analysis showed that the DEPs were most strongly associated with “response to stress” and “protein processing in endoplasmic reticulum”. Furthermore, several heat shock proteins were identified as DEPs. This information provides a reference direction for further research on the okra proteome in the downstream of the salt stress response, with our data revealing that the responses of okra to salt stress involves by various pathways.

The chaperonin 60 (Cpn60) protein is of great importance to plants due to its involvement in modulating the folding of numerous chloroplast protein polypeptides. In chloroplasts, Cpn60 is differentiated into two subunit types—Cpn60α and Cpn60β and the rice genome encodes three α and three β plastid chaperonin subunits. However, the functions of Cpn60 family members in rice were poorly understood. In order to investigate the molecular mechanism of OsCpn60β1, we attempted to disrupt the OsCpn60β1 gene by CRISPR/Cas9-mediated targeted mutagenesis in this study. We succeeded in the production of homozygous OsCpn60β1 knockout rice plants. The OsCpn60β1 mutant displayed a striking albino leaf phenotype and was seedling lethal. Electron microscopy observation demonstrated that chloroplasts were severely disrupted in the OsCpn60β1 mutant. In addition, OsCpn60β1 was located in the chloroplast and OsCpn60β1 is constitutively expressed in various tissues particularly in the green tissues. The label-free qualitative proteomics showed that photosynthesis-related pathways and ribosomal pathways were significantly inhibited in OsCpn60β1 mutants. These results indicate that OsCpn60β1 is essential for chloroplast development in rice.

The feasibility of using the fourier transform infrared (FTIR) spectroscopic technique with a stacked sparse auto-encoder (SSAE) to identify orchid varieties was studied. Spectral data of 13 orchids varieties covering the spectral range of 4000–550 cm⁻¹ were acquired to establish discriminant models and to select optimal spectral variables. K nearest neighbors (KNN), support vector machine (SVM), and SSAE models were built using full spectra. The SSAE model performed better than the KNN and SVM models and obtained a classification accuracy 99.4% in the calibration set and 97.9% in the prediction set. Then, three algorithms, principal component analysis loading (PCA-loading), competitive adaptive reweighted sampling (CARS), and stacked sparse auto-encoder guided backward (SSAE-GB), were used to select 39, 300, and 38 optimal wavenumbers, respectively. The KNN and SVM models were built based on optimal wavenumbers. Most of the optimal wavenumbers-based models performed slightly better than the all wavenumbers-based models. The performance of the SSAE-GB was better than the other two from the perspective of the accuracy of the discriminant models and the number of optimal wavenumbers. The results of this study showed that the FTIR spectroscopic technique combined with the SSAE algorithm could be adopted in the identification of the orchid varieties.

Background: The orchid is one of the top ten Chinese flowers and has high ornamental value and elegant color. However, orchids are vulnerable to abiotic stresses during their growth and development, and the molecular mechanism of the abiotic stress response in orchids is unclear. WRKY proteins belong to a transcription factor family that plays important roles in biotic stress, abiotic stress, growth and development in plants, but little is known about the WRKY family in Cymbidium goeringii. Methods: The specific fragment of the CgWRKY57 gene of C. goeringii was analyzed by bioinformatics. The expression of the CgWRKY57 gene of C. goeringii under 4 °C, 42 °C water and ABA stress as well as different tissues was detected by real-time fluorescence quantitative PCR. CgWRKY57 gene was overexpressed in wild type Arabidopsis thaliana by inflorescence infection method, and the function of transgenic lines under ABA stress was analyzed. Results: CgWRKY57 was cloned from C. goeringii and found to encode 303 amino acids. The CgWRKY57 protein is an acidic, nonsecreted hydrophilic protein without a signal peptide or transmembrane domain. The CgWRKY57 protein is located to the nucleus and may function intracellularly according to its predicted subcellular localization. A domain analysis and homology comparison showed that the CgWRKY57 protein has a “WRKYGQK” domain and belongs to Group III of the WRKY family, and a phylogenetic analysis demonstrated that CgWRKY57 is closely related to OsWRKY47. CgWRKY57 was expressed in the roots, stems, leaves and floral organs of C. goeringii, and its expression level was highest in the roots according to real-time qPCR analysis. There were significant differences in CgWRKY57 expression under 4 °C, 42 °C ABA and water stress treatments, and its expression changed greatly under ABA stress. The expression of CgWRKY57 in transgenic plants was significantly higher than that in wild type plants under ABA stress, and the root length and germination rate were reduced in transgenic plants compared to wild type plants. Conclusions: These results indicate that CgWRKY57 overexpression is responsive to ABA stress, and they provide a foundation for future analyses of the biological functions of the WRKY family in C. goeringii.

Background: The water-soluble Grifola frondosa polysaccharides (GFPs) are the primary bioactive component of the edible and medicinal fungus Grifola frondosa. However, the digestive behavior of GFPs in the human gastrointestinal (GI) tract and their subsequent interaction with gut microbiota (GM) to exert health effects remain unclear. Methods: In this study, GFPs were extracted based on a traditional hot water decoction. An in vitro simulated GI digestion model and a human fecal microbiota fermentation model were established to systematically investigate the digestive stability of GFPs, GM modulation, and metabolite changes. Results: Results showed that GFPs remained structurally stable during in vitro oral, gastric, and small intestinal digestion, allowing them to reach the colon intact for microbial fermentation. During colonic fermentation, GFPs were efficiently degraded by GM, and significantly increased the relative abundance of beneficial bacteria such as Akkermansia, Bacteroides, Parabacteroides, and Lactobacillus while reducing the abundance of pathogenic Escherichia-Shigella. Meanwhile, GFPs enriched metabolites beneficial for intestinal health, among which γ-aminobutyric acid (GABA) was the most significantly upregulated. Single-strain fermentation confirmed that Lactobacillus (L. plantarum) was the core GABA-producing genus. Conclusions: This study highlights the potential of GFPs as prebiotics for GM modulation, expands the understanding of the health-promoting effects of fungal polysaccharides, and provides a theoretical basis for the development of GFP-based functional foods.