In vitro propagation of Leucocroton havanensis Borhidi (Euphorbiaceae): A rare serpentine-endemic species of Cuba

Leucocroton havanensis Borhidi is an endemic plant species of Cuba able to hyperaccumulate nickel. In order to sustain the conservation of this species, an efficient protocol for its micropropagation, via axillary bud proliferation, is described. We placed apical segments from aseptic seedlings on basal medium supplemented with indole-3-acetic acid (IAA) and 6-benzylaminopurine (BAP) or thidiazuron (TDZ), individually or in combination. On a medium containing 0.5 mg L−1IAA and 1.0 mg L−1BAP explants (65.5%) developed axillary buds. Nevertheless, combinations of 0.5 mg L−1IAA with 0.1 mg L−1TDZ was the most effective treatment producing the highest number of buds per explant (30.3); while the control treatment, without growth regulators, produced no buds at all. Transfer of buds to medium supplemented with indole-3-butyric acid, indicated that 0.25 mg L−1is the amount of hormone required to generate roots on young buds (100%). In order to assess DNA variations in micropropagated plants, an Amplified Fragment Length Polymorphism analysis was performed and no genetic variation was detected. This study demonstrates that a high multiplication rate can be obtained by means of the reported protocol, and that plantlets can be readily hardened (96% survival) in a greenhouse by transplanting them on serpentine soil

Divergent roles of IREG/Ferroportin transporters from the nickel hyperaccumulator<i>Leucocroton havanensis</i>

International audienceIn response to our ever-increasing demand for metals, phytotechnologies are being developed to limit the environmental impact of conventional metal mining. However, the development of these technologies, which rely on plant species able to tolerate and accumulate metals, is partly limited by our lack of knowledge of the underlying molecular mechanisms. In this work, we aimed to identify genes involved in nickel hyperaccumulation in the Euphorbiaceae species Leucocroton havanensis . Using transcriptomic data, we identified two homologous genes, LhavIREG1 and LhavIREG2 , encoding divalent metal transporters of the IREG/ferroportin family. Both genes are expressed at similar levels in shoots, but LhavIREG1 shows higher expression in roots. Heterologous expression of these transporters in A. thaliana revealed that LhavIREG1 is localized to the plasma membrane, whereas LhavIREG2 is located at the vacuole. In addition, expression of each gene induced a significant increase in nickel tolerance. Taken together, our data suggest that LhavIREG2 is involved in nickel sequestration in vacuoles of leaf cells, whereas LhavIREG1 is mainly involved in nickel translocation from roots to shoots, but could also be involved in metal sequestration in cell walls. Our results suggest that paralogous IREG/ferroportin transporters may play complementary roles in nickel hyperaccumulation in plants. Highlight The nickel hyperaccumulator Leucocroton havanensis endemic to Cuba, expresses two paralogous metal transporters of the IREG/ferroportin family that play distinct but complementary roles in nickel tolerance and accumulation

Addressing the diversity of the mechanisms involved in metal hyperaccumulation in plants

International audienceThe extraordinary ability to accumulate and tolerate tremendous amounts of metals such as nickel, zinc, or manganese in their leaves has been observed in about 700 plant species belonging to more than 50 families. For many years, these metal hyperaccumulator species have attracted the attention of scientists interested in understanding the evolution of this complex and peculiar trait. In the context of the decarbonization of energy, metal hyperaccumulators appear as an opportunity to develop phytotechnologies aimed at limiting the metal pollution associated with to the growing demand for metals. However, our knowledge of the molecular mechanisms involved in metal hyperaccumulation, which is key to the development of these technologies, is still very limited.To extend our knowledge of the diversity of hyperaccumulator species, we participated in a global effort to identify new hyperaccumulator species using the X-ray fluorescence technology focusing on the flora of the neotropical region. Our herbarium and field studies revealed the first example of a zinc hyperaccumulator from the Amazonas region, as well as new nickel hyperaccumulators originating from Cuba.The identification of nickel hyperaccumulators and closely related non-hyperaccumulator species from different families has opened the possibility to perform comparative cross-species transcriptomic studies to identify orthologous genes whose expression is linked to nickel hyperaccumulation. Among candidate genes, our analyses revealed that the high expression in leaves of metal transporters of the IREG/ferroportin family is a highly conserved mechanism involved in nickel hyperaccumulation across distant plant species.We are now developing the multi-metal hyperaccumulator Noccaea caerulescens of the Brassicaceae family as a genetic model to validate and study the role of candidate genes in metal hyperaccumulation

Addressing the diversity of the mechanisms involved in metal hyperaccumulation in plants

International audienceThe extraordinary ability to accumulate and tolerate tremendous amounts of metals such as nickel, zinc, or manganese in their leaves has been observed in about 700 plant species belonging to more than 50 families. For many years, these metal hyperaccumulator species have attracted the attention of scientists interested in understanding the evolution of this complex and peculiar trait. In the context of the decarbonization of energy, metal hyperaccumulators appear as an opportunity to develop phytotechnologies aimed at limiting the metal pollution associated with to the growing demand for metals. However, our knowledge of the molecular mechanisms involved in metal hyperaccumulation, which is key to the development of these technologies, is still very limited.To extend our knowledge of the diversity of hyperaccumulator species, we participated in a global effort to identify new hyperaccumulator species using the X-ray fluorescence technology focusing on the flora of the neotropical region. Our herbarium and field studies revealed the first example of a zinc hyperaccumulator from the Amazonas region, as well as new nickel hyperaccumulators originating from Cuba.The identification of nickel hyperaccumulators and closely related non-hyperaccumulator species from different families has opened the possibility to perform comparative cross-species transcriptomic studies to identify orthologous genes whose expression is linked to nickel hyperaccumulation. Among candidate genes, our analyses revealed that the high expression in leaves of metal transporters of the IREG/ferroportin family is a highly conserved mechanism involved in nickel hyperaccumulation across distant plant species.We are now developing the multi-metal hyperaccumulator Noccaea caerulescens of the Brassicaceae family as a genetic model to validate and study the role of candidate genes in metal hyperaccumulation

Addressing the diversity of the mechanisms involved in metal hyperaccumulation in plants

International audienceThe extraordinary ability to accumulate and tolerate tremendous amounts of metals such as nickel, zinc, or manganese in their leaves has been observed in about 700 plant species belonging to more than 50 families. For many years, these metal hyperaccumulator species have attracted the attention of scientists interested in understanding the evolution of this complex and peculiar trait. In the context of the decarbonization of energy, metal hyperaccumulators appear as an opportunity to develop phytotechnologies aimed at limiting the metal pollution associated with to the growing demand for metals. However, our knowledge of the molecular mechanisms involved in metal hyperaccumulation, which is key to the development of these technologies, is still very limited.To extend our knowledge of the diversity of hyperaccumulator species, we participated in a global effort to identify new hyperaccumulator species using the X-ray fluorescence technology focusing on the flora of the neotropical region. Our herbarium and field studies revealed the first example of a zinc hyperaccumulator from the Amazonas region, as well as new nickel hyperaccumulators originating from Cuba.The identification of nickel hyperaccumulators and closely related non-hyperaccumulator species from different families has opened the possibility to perform comparative cross-species transcriptomic studies to identify orthologous genes whose expression is linked to nickel hyperaccumulation. Among candidate genes, our analyses revealed that the high expression in leaves of metal transporters of the IREG/ferroportin family is a highly conserved mechanism involved in nickel hyperaccumulation across distant plant species.We are now developing the multi-metal hyperaccumulator Noccaea caerulescens of the Brassicaceae family as a genetic model to validate and study the role of candidate genes in metal hyperaccumulation

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

This article has been accepted for publication in Metalomics Published by Oxford University Press. DOI: 10.1093/mtomcs/mfab045Plants have developed a diversity of strategies to take up and store essential metals in order to colonize various types of soils including mineralized soils. Yet, our knowledge of the capacity of plant species to accumulate metals is still fragmentary across the plant kingdom. In this study, we have used the X-Ray Fluorescence technology to analyze metal concentration in a wide diversity of species of the Neotropical flora that was not extensively investigated so far. In total, we screened more than 11 000 specimens representing about 5000 species from herbaria in Paris and Cuba. Our study provides a large overview of the accumulation of metals such as manganese, zinc and nickel in the Neotropical flora. We report 30 new nickel hyperaccumulating species from Cuba, including the first records in the families Connaraceae, Melastomataceae, Polygonaceae, Santalaceae and Urticaceae. We also identified the first species from this region of the world that can be considered as manganese hyperaccumulators in the genera Lomatia (Proteaceae), Calycogonium (Melastomataceae), Ilex (Aquifoliaceae), Morella (Myricaceae) and Pimenta (Myrtaceae). Finally, we report the first zinc hyperaccumulator, Rinorea multivenosa (Violaceae), from the Amazonas region. The identification of species able to accumulate high amounts of metals will become instrumental to support the development of phytotechnologies in order to limit the impact of soil metal pollution in this region of the world