Analysis of Gene Expression Associated with Copper Toxicity in White Birch (Betula papyrifera) Populations from a Mining Region

Abstract

The Greater Sudbury Region (GSR) is one of the most ecologically disturbed regions of Canada. Recent studies have shown that Betula papyrifera accumulate metals in roots or leaves. The main objectives of the present study were to 1) determine the effects of copper treatment on B. papyrifera under controlled conditions and 2) assess the level of expression of genes associated with copper resistance in B. papyrifera populations from metal-contaminated and uncontaminated areas. Significant differences for damage rating were observed among copper dosages after eight days of treatment. There was also a trend of reduced plant growth as the dosage increased. RT-qPCR analysis showed 2x to 25x increase in leaves compared to roots of the expression of the gene for Multi-drug resistance associated protein (MRP4) belonging to the subfamily of ATPbinding cassette (ABC) transporters. A significant upregulation (ranging from 3x to 8 x increase) of

Differential Gene Transcription in Red Oak (Quercus rubra) Genotypes Resistant to Copper Toxicity

“…Our results also contrast with data from other studies that focused on B. papyrifera (a hard wood species) showing a decrease in growth and the presence of leaf chlorosis and necrosis after exposure to copper (Djeukam et al, 2016) and nickel (Theriault and Nkongolo, 2016). However, Keller et al (2003) suggests that the root system surface may have an impact in the absorption of metals such as copper and potentially lead to a difference in assimilation of metals between these species (Keller et al, 2003).…”

“…The same effects were observed in other species such as Brassica juncea, Brassica napus (Feigl et al, 2013) and Triticum aestivum (Cook et al, 1997). Djeukam et al (2016) observed a reduction in the growth of B. papyrifera seedlings treated with copper at a concentration dose of 1312 mg/kg or more compared to a water control. In this study, growth of Q. rubra plants was not significantly affected by Cu at all the doses used (130, 656 and 1312 mg/kg) and their respective control treatments.…”

“…Total RNA was extracted from samples using the procedure described by Theriault and Nkongolo (2016;Djeukam et al, 2016). RNA was quantified using the Qubit RNA BR Assay kit from Life Technologies (Carlsbad, United States).…”

“…However, the second component of the solubilized salt, the sulfate ion, is also absorbed by the roots and can cause adverse effects to plants at high concentrations as demonstrated by Djeukam et al (2016). Indeed they showed the adverse effects of potassium sulfateon another woody species (Betula papyrifera) that was associated with an increase in concentrations (Djeukam et al, 2016). Therefore, it is important to consider the potential effects of this ion on phenotypic damage and gene transcription change, even at low concentrations.…”

“…Specifically, it can induce several symptoms such as chlorosis (Ali et al, 2002;Shahbaz et al, 2010;Feigl et al, 2013), necrosis (Drazkiewicz et al, 2004;Yruela, 2009;Foy et al, 1978;Barbosa et al, 2013;Aly and Mohamed, 2012) and inhibition of root and aerial plant tissue growth (Ali et al, 2002;Benimeli et al, 2010;Cook et al, 1997). In addition, recent studies have demonstrated the presence of such symptoms in woody plant species (Theriault and Nkongolo, 2016;Djeukam et al, 2016). It is therefore essential for plants to develop a mechanism to regulate copper homeostasis.…”