The mitogenome of Pseudocrossidium replicatum, a desiccation-tolerant moss

Novel Diterpenoids Incorporating Rearranged Labdanes from the Chinese Liverwort Anastrophyllum joergensenii and Their Anti-inflammatory Activity

Liverworts provide valuable ecological services to improve the sustainability of agriculture, encompassing soil health maintenance and natural pest management. Some liverworts have potential applications in medicine and as food additives. Twenty-two novel diterpenoids (anajoerins A-V), of which anajoerins B-G are rearranged labdanes featuring an unprecedented 6/5 fused ring system, were isolated from the Chinese liverwort Anastrophyllum joergensenii Schiffn. The absolute configurations of all compounds were identified based on high-resolution electrospray ionization mass spectroscopy data, NMR spectra, and ECD calculations. Plausible biogenetic pathways for unprecedented rearranged labdanes were proposed. Seven diterpenoids exhibited anti-inflammatory activity by reducing nitric oxide production in LPS-stimulated RAW264.7 murine macrophages in a dose-dependent manner with IC50s between 9.71 and 56.56 μM. All tested compounds showed no cytotoxicity at the tested concentrations. Western blot analyses of NF-κB p65 downregulation showed that anajoerin L could inhibit the NF-κB signaling pathway. Furthermore, anajoerin L also suppressed the secretion of the ConA-induced proinflammatory cytokines IFN-γ, TNF-α, and IL-6.

Complete chloroplast and mitochondrial genomes of Ditrichum rhynchostegium Kindb. (Ditrichaceae, Bryophyta)

The moss family Pottiaceae is one of the most diverse lineages of the subclass Dicranidae (haplolepideous mosses). Nevertheless, the phylogenetic relationships of Pottiaceae with other Dicranidae families remain unclear. To better understand the ancestral genomic structure and evolution of the Pottiaceae, herein, we present the chloroplast and mitochondrial genomes of Ditrichum rhynchostegium (Ditrichaceae, Bryophyta). The chloroplast genome is 124,628 bp long and displayed a circular structure composed of a large single-copy region, a small single-copy region, and a pair of inverted repeats. It has 118 genes, including 82 protein-coding genes, 32 tRNA genes, and four rRNA genes. The mitochondrial genome is 106,246 bp long and has a circular structure. It contains 67 genes, including 40 protein-coding genes, 24 tRNA genes, and three rRNA genes. Phylogenetic trees based on the coding sequences strongly support the sister relationship of D. rhynchostegium with all Pottiaceous accessions, and the dextrosely arranged operculum cells suggest its affinity for Pottiaceae. This study also demonstrates that long-read sequencing employing the Nanopore platform facilitates the repair of unassembled or misassembled organellar genomic regions.

The complete chloroplast and mitochondrial genomes of Scopelophila cataractae (Mitt.) Broth. (Pottiaceae, Bryophyta)

The complete chloroplast and mitochondrial genome sequences of Scopelophila cataractae (Pottiaceae, Bryophyta) are determined. The chloroplast genome is 122,290 bp with 118 genes and the mitochondrial genome is 105,607 bp with 67 genes, both genomes are circular. This study showed the S. cataractae plastome contains the smallest genome size, and a functional trnP^GGG gene, relative to other pottiaceous species. Phylogenetic inferences support the sister relationship of S. cataractae to all other pottiaceous accessions. 

Pseudocrossidium replicatum (Taylor) R.H. Zander is a fully desiccation-tolerant moss that expresses an inducible molecular mechanism in response to severe abiotic stress

KEY MESSAGE

The moss Pseudocrossidium replicatum is a desiccation-tolerant species that uses an inducible system to withstand severe abiotic stress in both protonemal and gametophore tissues. Desiccation tolerance (DT) is the ability of cells to recover from an air-dried state. Here, the moss Pseudocrossidium replicatum was identified as a fully desiccation-tolerant (FDT) species. Its gametophores rapidly lost more than 90% of their water content when exposed to a low-humidity atmosphere [23% relative humidity (RH)], but abscisic acid (ABA) pretreatment diminished the final water loss after equilibrium was reached. P. replicatum gametophores maintained good maximum photosystem II (PSII) efficiency (Fv/Fm) for up to two hours during slow dehydration; however, ABA pretreatment induced a faster decrease in the Fv/Fm. ABA also induced a faster recovery of the Fv/Fm after rehydration. Protein synthesis inhibitor treatment before dehydration hampered the recovery of the Fv/Fm when the gametophores were rehydrated after desiccation, suggesting the presence of an inducible protective mechanism that is activated in response to abiotic stress. This observation was also supported by accumulation of soluble sugars in gametophores exposed to ABA or NaCl. Exogenous ABA treatment delayed the germination of P. replicatum spores and induced morphological changes in protonemal cells that resembled brachycytes. Transcriptome analyses revealed the presence of an inducible molecular mechanism in P. replicatum protonemata that was activated in response to dehydration. This study is the first RNA-Seq study of the protonemal tissues of an FDT moss. Our results suggest that P. replicatum is an FDT moss equipped with an inducible molecular response that prepares this species for severe abiotic stress and that ABA plays an important role in this response.