Abstract
Cadmium (Cd) is a toxic metal occurring in the environment naturally. Almond mushroom (Agaricus brasiliensis) is a well-known cultivated edible and medicinal mushroom. In the past few decades, Cd accumulation in A.brasiliensis has received increasing attention. However, the molecular mechanisms of Cd-accumulation in A. brasiliensis are still unclear. In this paper, a comparative transcriptome of two A.brasiliensis strains with contrasting Cd accumulation and tolerance was performed to identify Cd-responsive genes possibly responsible for low Cd-accumulation and high Cd-tolerance. Using low Cd-accumulating and Cd-tolerant (J77) and high Cd-accumulating and Cd-sensitive (J1) A.brasiliensis strains, we investigated 0, 2 and 5 mg L-1 Cd-effects on mycelium growth, Cd-accumulation and transcriptome revealed by RNA-Seq. A total of 57,884 unigenes were obtained. Far less Cd-responsive genes were identified in J77 mycelia than those in J1 mycelia (e.g., ABC transporters, ZIP Zn transporter, Glutathione S-transferase and Cation efflux (CE) family). The higher Cd-accumulation in J1 mycelia might be due to Cd-induced upregulation of ZIP Zn transporter. Cd impaired cell wall, cell cycle, DNA replication and repair, thus decreasing J1 mycelium growth. Cd-stimulated production of sulfur-containing compounds, polysaccharides, organic acids, trehalose, ATP and NADPH, and sequestration of Cd might be adaptive responses of J1 mycelia to the increased Cd-accumulation. DNA replication and repair had better stability under 2 mg L-1 Cd, but greater positive modifications under 5 mg L-1 Cd. Better stability of DNA replication and repair, better cell wall and cell cycle stability might account for the higher Cd-tolerance of J77 mycelia. Our findings provide a comprehensive set of DEGs influenced by Cd stress; and shed light on molecular mechanism of A.brasiliensis Cd accumulation and Cd tolerance.
Highlights
Almond mushroom (Agaricus brasiliensis), one of the important cultivated edible mushrooms and natural foods, has been produced on an industrial scale in Brazil, China and Japan [1,2]
J77 mycelia were more tolerant to Cd-stress than J1 mycelia. This might be related to the finding that Cd concentration was higher in J1 mycelia than that in J77 mycelia at each given Cd supply (Fig 1b)
Cd-induced upregulation of ZIP might contribute to the higher Cd accumulation in Cdtreated J1 mycelia
Summary
Almond mushroom (Agaricus brasiliensis), one of the important cultivated edible mushrooms and natural foods, has been produced on an industrial scale in Brazil, China and Japan [1,2]. Cadmium (Cd), one of a nonessential and natural element, is potentially hazardous to animal and human health. High concentration of Cd, up to 100–300 mg kg-1 dry matter (DM) was observed in the genus Agaricus [10]. Cd concentrations in A. brasiliensis ranged from 3–30 mg kg-1 DM, which was higher than that in many edible mushroom species [11]. Cd accumulation in A. brasiliensis could potentially affect food safety and eventually have a direct or indirect threat to human health [12]. Cd-accumulation in A. brasiliensis has received increasing concerns
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