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Tanakaea radicans is classified in the monotypic genus Tanakaea in the Saxifragaceae. It is a small, evergreen plant with a disjunct distribution in Japan and China. Here, we report and characterize for the first time the complete plastid genome sequence of T. radicans. The chloroplast genome is 155,265 bp in length and contains a pair of inverted repeats (25,794 bp) separated by a large single copy (86,289 bp) and a small single copy (17,388 bp). A total of 113 unique genes, including 79 protein-coding, 30 tRNA, and four rRNA genes, were annotated. Phylogenetic analysis showed that T. radicans was sister to Leptarrhena pyrolifolia within Huecheroids linage of Saxifragaceae.

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Cadmium (Cd) is one of the most toxic metals in the environment and exerts deleterious effects on plant growth and production. Duckweed has been reported as a promising candidate for Cd phytoremediation. In this study, the growth, Cd enrichment, and antioxidant enzyme activity of duckweed were investigated. We found that both high-Cd-tolerance duckweed (HCD) and low-Cd-tolerance duckweed (LCD) strains exposed to Cd were hyper-enriched with Cd. To further explore the underlying molecular mechanisms, a genome-wide transcriptome analysis was performed. The results showed that the growth rate, chlorophyll content, and antioxidant enzyme activities of duckweed were significantly affected by Cd stress and differed between the two strains. In the genome-wide transcriptome analysis, the RNA-seq library generated 544,347,670 clean reads, and 1608 and 2045 differentially expressed genes were identified between HCD and LCD, respectively. The antioxidant system was significantly expressed during ribosomal biosynthesis in HCD but not in LCD. Fatty acid metabolism and ethanol production were significantly increased in LCD. Alpha-linolenic acid metabolism likely plays an important role in Cd detoxification in duckweed. These findings contribute to the understanding of Cd tolerance mechanisms in hyperaccumulator plants and lay the foundation for future phytoremediation studies.