Wide cross‐species RNA‐Seq comparison reveals convergent molecular mechanisms involved in nickel hyperaccumulation across dicotyledons

Abstract

The Anthropocene epoch is associated with the spreading of metals in the environment increasing oxidative and genotoxic stress on organisms. Interestingly, c. 520 plant species growing on metalliferous soils acquired the capacity to accumulate and tolerate a tremendous amount of nickel in their shoots. The wide phylogenetic distribution of these species suggests that nickel hyperaccumulation evolved multiple times independently. However, the exact nature of these mechanisms and whether they have been recruited convergently in distant species is not known. To address these questions, we have developed a cross-species RNA-Seq approach combining differential gene expression analysis and cluster of orthologous group annotation to identify genes linked to nickel hyperaccumulation in distant plant families. Our analysis reveals candidate orthologous genes encoding convergent function involved in nickel hyperaccumulation, including the biosynthesis of specialized metabolites and cell wall organization. Our data also point out that the high expression of IREG/Ferroportin transporters recurrently emerged as a mechanism involved in nickel hyperaccumulation in plants. We further provide genetic evidence in the hyperaccumulator Noccaea caerulescens for the role of the NcIREG2 transporter in nickel sequestration in vacuoles. Our results provide molecular tools to better understand the mechanisms of nickel hyperaccumulation and study their evolution in plants.

The X-ray fluorescence screening of multiple elements in herbarium specimens from the Neotropical region reveals new records of metal accumulation in plants

“…72 For example the Mn hyperaccumulator and putative nitrogen fixer Morella shaferi, represents a good candidate species for the restoration of degraded soils in Cuba and Mn accumulated in its biomass could be recycled to produce Mn for green chemistry. 73 The identification metal hyperaccumulators, as well as the identification of related non-accumulator species in a large diversity of plant families is a prerequisite to identify the genes involved in metal accumulation in plants using comparative studies [74][75][76] . S2).…”

Contrasting patterns of nickel distribution in the hyperaccumulatorsPhyllanthus balgooyiandPhyllanthus rufuschaneyifrom Malaysian Borneo

“… 10 This was confirmed in a recent study undertaking an RNA-Seq comparison in Ni hyperaccumulator species from New Caledonia and Cuba, which revealed convergent molecular mechanisms with high expression of IREG/Ferroportin transporters linked to Ni hyperaccumulation. 73 There remains, therefore, much scope for research in this space to identify the molecular pathways of Ni during uptake in the root and the associated cell membrane transporters involved.…”

A New Species of Argophyllum (Argophyllaceae) with Notes on the Species from New Caledonia and Nickel Hyperaccumulation

“…For each species, we selected specimens to represent their morphological, geographical and ecological range. For a putative new species, one leaf from five individuals was collected in the field, dried, ground to powder, digested in HNO 3 /H 2 O 2 and analysed by Microwave Plasma-Atomic Emission Spectrometer (MP-AES) [32].…”