<i>De novo</i> transcriptome analysis reveals an unperturbed transcriptome under high cadmium conditions in the Cd-hypertolerant fern <i>Athyrium yokoscense</i>

Abstract

Athyrium yokoscense shows strong tolerance to cadmium exposure, even at levels that are many times greater than the toxic levels in ordinary plants. To determine the mechanism of Cd tolerance in A. yokoscense, we grew these plants under high Cd conditions and observed the tissue-specific accumulation of Cd and generation of reactive oxygen species, which is one of the major physiological responses to Cd stress. Fuchsin staining indicated the existence of a casparian strip in A. yokoscense roots, which may participate in Cd hypertolerance in A. yokoscense. Moreover, we performed RNA-seq of RNA samples from A. yokoscense plants treated with or without Cd exposure and obtained comprehensive RNA sequences as well as the Cd-responsive expression patterns of individual genes. Through de novo transcriptome assembly and gene expression analysis, we found that A. yokoscense showed normal features with no significant change in the expression levels of any transporter genes, even under high Cd exposure conditions. Our results demonstrate that A. yokoscense has an unusual mechanism that allows the invading Cd to partition into the distal roots, thus avoiding translocation of Cd into the xylem.

The cadmium-hypertolerant fern,Athyrium yokoscense, exhibits two cadmium stress mitigation strategies in the roots and the aerial parts

“…In the roots of A. yokoscense, the existence of a Casparian strip has been suggested (Ukai et al 2020). This might restrict Cd intrusion into the central region.…”

“…OsNramp5 is Nramp family transporter located on the cell membrane of Oryza sativa, which is involved in Mn and Fe transport in their roots. We have reported the cDNA dataset that was established by RNA-seq analysis of A. yokoscense cells (Ukai et al 2020). This report has revealed that A. yokoscense has eight genes encoding proteins…”

Full-length transcriptome analysis of Adiantum flabellulatum gametophyte

“…Based on the Illumina HiSeq sequencing platform, the transcriptomes of roots and shoots of Athyrium yokoscense ( Ukai et al, 2020 ), young leaves of Asplenium nidus , young leaves of Asplenium komarovii ( Zhang et al, 2019 ) and sexual reproduction and apogamy of Adiantum reniforme gametophytes ( Fu & Chen, 2019 ) were studied, and 35,681, 89,741, 77,912, 333,352, 264,791 transcripts were obtained, respectively. The sequencing read length of the Illumina HiSeq is short, the mRNAs need to be broken into short fragments before sequencing, and the complete transcripts can be obtained only by splicing.…”

Lead and Cadmium Tolerance and Accumulation of Proanthocyanidin-Deficient mutants of the Fern Athyrium yokoscense

“…Recently, Ukai et al 22 performed an RNA-seq analysis of A. yokoscense sporophytes exposed or not to Cd and found few significant changes in the A. yokoscense Article transcriptome, even under high Cd conditions. These results imply that most genes involved in Cd tolerance and accumulation may be constitutively expressed in A. yokoscense, regardless of the presence or absence of Cd, like the case of Arabidopsis halleri, a facultative Cd and Zn hyperaccumulator.…”

“…These results imply that most genes involved in Cd tolerance and accumulation may be constitutively expressed in A. yokoscense, regardless of the presence or absence of Cd, like the case of Arabidopsis halleri, a facultative Cd and Zn hyperaccumulator. 23 Interestingly, however, Ukai et al 22 also found that the level of an NPF ortholog, which is a putative nitrate transporter gene, doubled in response to Cd stress in the roots. For plants, owing to its low availability, nitrogen is the critical limiting element.…”