Proteomic profiling uncovered the cytosolic superoxide dismutase BsSOD1 associated with plant defence in the herbal orchid Bletilla striata

Phosphorylation of 399S at CsHsp70 of Cymbidium sinense is essential to maintain chlorophyll stability

The Chinese orchids symbolise nobility and gentility in China, and the variation of leaf color makes Cymbidium sinense more diversified and valuable. However, its color variations especially at the protein level still remain largely unexplored. In this study, the proteomics and phosphoproteomics of Cymbidium sinense leaf color variation mutants were studied. A total of 1059 differentially abundant proteins (DAPs) and 1127 differentially abundant phosphorylation sites belonging to 644 phosphoproteins (DAPPs) were identified in the yellow section of leaf variegation mutant of Cymbidium sinense (MY) compared with the green section (MG). Moreover, 349 co-expressing proteins were found in both omics' datasets, while only 26 proteins showed the same expression patterns in the two omics. The interaction network analysis of kinases and phosphatases showed that DAPs and DAPPs in photosynthesis, response to hormones, pigment metabolic process, phosphorylation, glucose metabolic process, and dephosphorylation might contribute to leaf color variation. The abundance of 28 Hsps and 28 phosphorylation sites belonging to 10 Hsps showed significant differences between MG and MY. CsHsp70 was selected to explore the function in Cymbidium sinense leaf variegation. The results showed CsHsp70 is essential for maintaining photosynthetic pigment content and the 399S phosphorylation site is crucial to the function of CsHsp70. Collectively, our findings construct a comprehensive coverage of protein and protein phosphorylation in leaf variegation of C. sinense, providing valuable insights into its formation mechanisms.

Cytochemical localization and synthesis mechanism of the glucomannan in pseudobulbs of Bletilla striata Reichb. f

The dried pseudobulbs of Bletilla striata, an important traditional Chinese medicine named BaiJi, have an extraordinary polysaccharide content and excellent prospects for medicinal effects. However, the distribution and molecular mechanism underlying biosynthesis are poorly understood. In this study, chemical and immunologic analyses were performed in representative tissues of B. striata, and the results showed that what are conventionally termed Bletilla striata polysaccharides (BSPs) are water-soluble polysaccharides deposited only in pseudobulbs. The structural component of BSPs is glucomannan, with a mannose:glucose mass ratio of ~3:2. BSPs are present in the parenchyma of the pseudobulbs in cells known as glucomannan idioblasts and distributed in the cytoplasm within cellular membranes, but are not contained in the vacuole. Comparative transcriptomics and bioinformatics analyses mapped the pathway from sucrose to BSP and identified BsGPI, BsmanA, and BsCSLAs as the key genes of BSP biosynthesis, suggesting that the functional differentiation of the cellulose synthase-like family A (CSLA) may be critical for the flow of glucomannan to the BSP or cell wall. Subsequently, virus-mediated gene silencing showed that silencing of two CSLAs (Bs03G11846 and Bs03G11849) led to a decrease in BSP content, and yeast two-hybrid and luciferase complementation experiments confirmed that four CSLAs (Bs03G11846, Bs03G11847, Bs03G11848, and Bs03G11849) can form homo- or heterodimers, suggesting that multiple CSLAs may form a large complex that functions in BSP synthesis. Our results provide cytological evidence of BSP and describe the isolation and characterization of candidate genes involved in BSP synthesis, laying a solid foundation for further research on its regulation mechanisms and the genetic engineering breeding of B. striata.

Proteomic Analysis of Apple Response to Penicillium expansum Infection Based on Label-Free and Parallel Reaction Monitoring Techniques

Blue mold, caused by Penicillium expansum, is the most destructive fungal disease of apples and causes great losses during the post-harvest storage of the fruit. Although some apple cultivars are resistant to P. expansum, there has been little information on the molecular mechanism of resistance. In this study, differential proteomic analysis was performed on apple samples infected and uninfected with P. expansum. Parallel reaction monitoring (PRM) technology was used to target and verify the expression of candidate proteins. The label-free technique identified 343 differentially expressed proteins, which were mainly associated with defense responses, metal ion binding, stress responses, and oxidative phosphorylation. The differential expression of enzymes related to reactive oxygen species (ROS) synthesis and scavenging, the activation of defense-related metabolic pathways, and the further production of pathogenesis-related proteins (PR proteins) during P. expansum infection in apples, and direct resistance to pathogen invasion were determined. This study reveals the mechanisms of apple response at the proteomic level with 9 h of P. expansum infection.

Haplotype-resolved genome assembly of Bletilla striata (Thunb.) Reichb.f. to elucidate medicinal value

Bletilla striata, commonly known as baiji, is a species used in traditional Chinese medicine; it is highly regarded for its medicinal applications and therefore has high economic value. Here, we report a high-quality haplotype-resolved genome of B. striata, haplotype A (2.37 Gb, with a scaffold N50 of 146.39 Mb and a contig N50 of 1.65 Mb) and haplotype B (2.43 Gb, with a scaffold N50 of 150.22 Mb and a contig N50 of 1.66 Mb), assembled from high-fidelity (HiFi) reads and chromosome conformation capture (Hi-C) reads. We find evidence that B. striata has undergone two whole-genome duplication (WGD) events: an ancient WGD event shared by most monocots and a recent WGD event unique to all orchids. We also reconstructed the ancestral orchid karyotype (AOK) of 18 ancient chromosomes and the evolutionary trajectories of 16 modern B. striata chromosomes. Comparative genomic analysis suggests that the expanded gene families of B. striata might play important roles in secondary metabolite biosynthesis and environmental adaptation. By combining genomic and transcriptomic data, we identified the 10 core members from nine gene families that were probably involved in B. striata polysaccharide (BSP) biosynthesis. Based on virus-induced gene silencing (VIGS) and yeast two-hybrid experiments, we present an MYB transcription factor (TF), BsMYB2, that can regulate BSP biosynthesis by directly interacting with eight key BSP-related genes: sacA1, HK1, scrK1, scrK2, GPI1, manA1, GMPP1 and UGP2_1. Our study will enhance the understanding of orchid evolution and accelerate the molecular-assisted breeding of B. striata for improving traits of medicinal value.

Organ-specific, integrated omics data-based study on the metabolic pathways of the medicinal plant Bletilla striata (Orchidaceae)

BACKGROUND

Bletilla striata is one of the important species belonging to the Bletilla genus of Orchidaceae. Since its extracts have an astringent effect on human tissues, B. striata is widely used for hemostasis and healing. Recently, some other beneficial effects have also been uncovered, such as antioxidation, antiinflammation, antifibrotic, and immunomodulatory activities. As a key step towards a thorough understanding on the medicinal ingredient production in B. striata, deciphering the regulatory codes of the metabolic pathways becomes a major task.

RESULTS

In this study, three organs (roots, tubers and leaves) of B. striata were analyzed by integrating transcriptome sequencing and untargeted metabolic profiling data. Five different metabolic pathways, involved in polysaccharide, sterol, flavonoid, terpenoid and alkaloid biosynthesis, were investigated respectively. For each pathway, the expression patterns of the enzyme-coding genes and the accumulation levels of the metabolic intermediates were presented in an organ-specific way. Furthermore, the relationships between enzyme activities and the levels of the related metabolites were partially inferred. Within the biosynthetic pathways of polysaccharides and flavonoids, long-range phytochemical transportation was proposed for certain metabolic intermediates and/or the enzymes.

CONCLUSIONS

The data presented by this work could strengthen the molecular basis for further studies on breeding and medicinal uses of B. striata.