Physiological and Transcriptomic Response of Grey Poplar (Populus ×Canescens Aiton Sm.) to Cadmium Stress

Abstract

Background: Populus ×canescens (Aiton) Sm. is a fast-growing woody plant belonging to the family Salicaceae. Thanks to its deep root system and fast growth rate, two poplar genotypes (TP11 and TP20) was chosen to be characterized and tested for a physiological and transcriptomic response to Cd stress.Results: Both sexual and clonal reproduction are common in grey poplar. Thus, to reveal its genetic structure, two selected poplar genotypes characterized by unique phenotypic traits were distinguished by microsatellite analysis. A comparative analysis of the effects of exposure to high cadmium (Cd) concentrations on the physiological response of TP11 and TP20 was performed. After 2 and 10 days, 10 µM and 100 µM Cd were added to the nutrient solution of poplar plants grown in perlite. Neither tested Cd concentration negatively affected plant growth; however, the chlorophyll content significantly decreased. According to mineral uptake analysis, the potassium (K) content was higher in the shoots than in the roots. The calcium (Ca) and magnesium (Mg) concentrations were only slightly affected by Cd treatment. The zinc (Zn) content in the shoots of TP20 was lower than that in the shoots of TP11. Moreover, the amount of Zn was slightly higher in the shoots of both genotypes after 10 days of Cd treatment compared to the control conditions. Cd accumulation was higher in the roots than in the shoots. After 2 days of 100 µM Cd treatment, TP11 accumulated significantly more Cd in the roots than TP20. After 10 days of exposure, 10 µM Cd resulted in comparable amounts of Cd in the roots and shoots of TP20, which was reflected in a translocation factor (TF) value greater than 1. Quantitative real-time RT-PCR analyses were used to examine the expression profiles of selected stress-response genes in the roots and shoots of plants exposed to Cd. The most significant change in transcript amount was observed in endochitinase 2, 12-oxophytodienoate reductase 1 and phi class glutathione S-transferase, which have been characterized as stress-response genes.Conclusions: Our study provided new insights for effective assessing the ability of different poplar genotypes to tolerate Cd stress and underlying Cd tolerance.