Transcriptome changes in Hirschfeldia incana in response to lead exposure

Hirschfeldia incana, a pseudometallophyte belonging to the Brassicaceae family and widespread in the Mediterranean region, was selected for its ability to grow on soils contaminated by lead (Pb). The global comparison of gene expression using microarrays between a plant susceptible to Pb (Arabidopsis thaliana) and a Pb tolerant plant (H. incana) enabled the identification of a set of specific genes expressed in response to lead exposure. Three groups of genes were particularly over-represented by the Pb exposure in the biological processes categorized as photosynthesis, cell wall, and metal handling. Each of these gene groups was shown to be directly involved in tolerance or in protection mechanisms to the phytotoxicity associated with Pb. Among these genes, we demonstrated that MT2b, a metallothionein gene, was involved in lead accumulation, confirming the important role of metallothioneins in the accumulation and the distribution of Pb in leaves. On the other hand, several genes involved in biosynthesis of ABA were shown to be up regulated in the roots and shoots of H. incana treated with Pb, suggesting that ABA-mediated signaling is a possible mechanism in response to Pb treatment in H. incana. This latest finding is an important research direction for future studies

Effect of lead on root growth

Lead (Pb) is one of the most widespread heavy metal contaminant in soils. It is highly toxic to living organisms. Pb has no biological function but can cause morphological, physiological, and biochemical dysfunctions in plants. Plants have developed a wide range of tolerance mechanisms that are activated in response to Pb exposure. Pb affects plants primarily through their root systems. Plant roots rapidly respond either (i) by the synthesis and deposition of callose, creating a barrier that stops Pb entering (ii) through the uptake of large amounts of Pb and its sequestration in the vacuole accompanied by changes in root growth and branching pattern or (iii) by its translocation to the aboveground parts of plant in the case of hyperaccumulators plants. Here were view the interactions of roots with the presence of Pb in the rhizosphere and the effect of Pb on the physiological and biochemical mechanisms of root development

Zinc hyperaccumulation in plants : a review

Zinc is an essential microelement involved in many aspects of plant growth and development. Abnormal zinc amounts, mostly due to human activities, can be toxic to flora, fauna, and humans. In plants, excess zinc causes morphological, biochemical, and physiological disorders. Some plants have the ability to resist and even accumulate zinc in their tissues. To date, 28 plant species have been described as zinc hyperaccumulators. These plants display several morphological, physiological, and biochemical adaptations resulting from the activation of molecular Zn hyperaccumulation mechanisms. These adaptations can be varied between species and within populations. In this review, we describe the physiological and biochemical as well as molecular mechanisms involved in zinc hyperaccumulation in plants

Biotechnologies végétales, amélioration des plantes, risques et stratégies alimentaires

Les arbres tropicaux de la famille des casuarinacées sont capables d'établir une symbiose avec un actinomycète du sol, #Frankia. La relation plante-micro-organisme se traduit par la différenciation de nodules racinaires qui ont la propriété de fixer l'azote atmosphérique. Grâce à leurs faibles exigences nutritionnelles et à leur remarquable tolérance à la sécheresse, ces arbres jouent un rôle important dans les régions tropicales, à la fois pour la protection des sols et la production de bois ou de biomasse. L'utilisation d'un vecteur biologique naturel, #Agrobacterium tumefaciens, a permis la mise au point d'une technique de transformation génétique chez deux espèces de casuarinacées : #Allocasuarina verticillata et #Casuarina glauca. Des plantes transgéniques ont été régénérées, caractérisées et leur aptitude à développer des nodules fonctionnels après inoculation par #Frankia a été montrée. La maîtrise d'une technique de transfert génétique, alliée à l'utilisation des outils de la biologie moléculaire, permettra d'obtenir de nombreuses informations sur les échanges moléculaires entre #Casuarina et #Frankia, et d'améliorer les performances de ce système symbiotique. Par une bonne connaissance des mécanismes contribuant à la régulation de l'expression chez #Casuarina, l'introduction de gènes d'intérêt dans ces ligneux tropicaux peut être envisagée et devrait contribuer à accélérer les programmes d'amélioration génétique de ces arbres. (Résumé d'auteur

Evaluation de la contamination par les éléments-traces métalliques dans une zone minière du Maroc oriental = Assessment of contamination by metallic trace elements in a mining area of eastern Morocco

La contamination des sols et des résidus miniers dans la région orientale du Maroc a été évaluée par dosage des éléments-traces métalliques (ETM) (As, Cd, Cu, Ni, Pb et Zn) par ICP-AES (inductively coupled plasma-atomic emission spectrometry). Ce travail révèle une contamination importante des sites étudiés et souligne une grande variabilité dans les concentrations en ETM en fonction de l_élément analysé et du site étudié. L'index de pollution des stations étudiées est généralement trés élevé du fait de la présence simultaneée de plusieurs de ces éléments. Cette combinaison de différents ETM rend les sols de la région toxiques pour la flore, la faune et les populations locales. Une analyse des espèces végétales qui se développent sur ces zones polluées est envisagée dans le cadre de la mise en place d'un programme de phytoremédiatio

Assessment of lead tolerance and accumulation in metallicolous and non-metallicolous populations of Hirschfeldia incana

Hirschfeldia incana is a pseudometallophyte belonging to the Brassicaceae family identified in a lead (Pb) mining area in eastern Morocco. Growth, Pb accumulation and some physiological characteristics were compared in a metallicolous (MP) and a non-metallicolous population (NMP) of H. incana. Plants from the MP were more tolerant to Pb than those from the NMP in both soil and hydroponic culture. In hydroponic culture, when supplied with 100 mu M of Pb, Pb accumulation in the aboveground parts of NMP plants was 2.5 times higher than in MP plants. MP plants had significantly lower concentrations of anthocyanins and higher concentrations of chlorophyll a than NMP. Molecular analyses revealed that HMA4 and MRP14 genes were regulated by Pb in the leaves of both MP and NMP. Interestingly, the MRP14 gene was constitutively more expressed in NMP suggesting possible adaptation of the MP via regulation of Pb accumulation. Our results show that plants from the metallicolous population has adapted to tolerate and accumulate Pb and thus have good potential for phytoremediation of Pb contaminated soil

État des lieux du site de la fonderie de l’Oued El Heimer : Opportunités ou Menaces ?

International audienc

État des lieux du site de la fonderie de l’Oued El Heimer : Opportunités ou Menaces ?

International audienc