Effects of copper accumulation on growth and development of Scopelophila cataractae grown in vitro

Scopelophila cataractae was cultured in vitro for 16 weeks to assess the contrasting effects of Cu on growth and reproduction, as well as gametophore stage. To induce buds and gametophores of S. cataractae, ten treatments (tr 1 to tr 10) of culture media were prepared using a combination of mineral salts, sugar, vitamin B complex, CuSO₄, and exogenous hormones. Highest numbers of gametophores and buds were formed in media containing 500 µM CuSO₄ in co-application with auxin and cytokinin, as shown in the modest Cu treatments (tr 6 and tr 7, 26 per cushion and 255 per 25 mm², respectively). A 5000 µM CuSO₄ concentration inhibited development of protonema, possibly due to Cu toxicity, resulting in chloronema forming contorted filaments or short cells containing lipid bodies, and brood body diaspores but no gametophore or bud formation. In this study, S. cataractae Cu accumulation in tissue was substantial (up to 2843.1 mg kg^-1; tr 6) with no or minimal adverse effects, reflecting its potential for phytoremediation of Cu in terrestrial and aquatic ecosystems. The highest atomic percentages of Cu and Zn were detected in the stem surfaces of gametophores treated with 500 µM CuSO₄ (11% atomic Cu and 7% atomic Zn), which served as a primary heavy metal storage site, ultimately protecting cells from metal toxicity. The success of this in vitro study on S. cataractae should also aid ex situ conservation efforts for a variety of rare moss taxa in the wild.

Heavy Metal Accumulation and Copper Localization in Scopelophila cataractae in Thailand

Four specimens of gametophores and protonemata of Scopelophila cataractae (copper moss) were collected from a stream in Doi Suthep-Pui National Park, Thailand in order to determine heavy metal accumulation and Cu localization. The order of total metal concentrations in the protonemata and leaf cell surfaces of S. cataractae was Fe > Zn > Cu. Significant Cu values (> 400 mg kg^-1) were found in both gametophores and protonemata. Growth substrates were considered as a key source of heavy metals in the sampling stream. X-ray spectrometry (EDS micro-analyser) detected the localization of ten elements (C, O, Mg, Al, Si, Ca, S, Cu, Zn and In); substantial atomic percentages of Al, Cu and Zn were noted in leaf surfaces and protonemata. These metallic elements were found in highest proportion. To some extent, cell surfaces at the basal leaf costa showed the highest peak value compared to medial and apical leaf portions (≈ 4.3 at.%). This Cu moss can be used as a bioindicator to reflect anthropogenic activities in stream ecosystems.

Efficient and Heritable Targeted Mutagenesis in Mosses Using the CRISPR/Cas9 System

Targeted genome modification by RNA-guided nucleases derived from the clustered regularly interspaced short palindromic repeat (CRISPR)/CRISPR-associated nuclease 9 (Cas9) system has seen rapid development in many organisms, including several plant species. In the present study, we succeeded in introducing the CRISPR/Cas9 system into the non-model organism Scopelophila cataractae, a moss that exhibits heavy metal tolerance, and the model organism Physcomitrella patens Utilizing the process by which moss plants regenerate from protoplasts, we conducted targeted mutagenesis by expression of single-chain guide RNA (sgRNA) and Cas9 in protoplasts. Using this method, the acquisition rate of strains exhibiting phenotypic changes associated with the target genes was approximately 45-69%, and strains with phenotypic changes exhibited various insertion and deletion mutations. In addition, we report that our method is capable of multiplex targeted mutagenesis (two independent genes) and also permits the efficient introduction of large deletions (∼3 kbp). These results demonstrate that the CRISPR/Cas9 system can be used to accelerate investigations of bryology and land plant evolution.