Copper Regulates Primary Root Elongation Through PIN1-Mediated Auxin Redistribution

Abstract

The heavy metal copper (Cu) is an essential microelement required for normal plant growth and development, but it inhibits primary root growth when in excess. The mechanism underlying how excess Cu functions in this process remains to be further elucidated. Here, we report that a higher concentration of CuSO4 inhibited primary root elongation of Arabidopsis seedlings by affecting both the elongation and meristem zones. In the meristem zone, meristematic cell division potential was reduced by excess Cu. Further experiments showed that Cu can modulate auxin distribution, resulting in higher auxin activities in both the elongation and meristem zones of Cu-treated roots based on DR5::GUS expression patterns. This Cu-mediated auxin redistribution was shown to be responsible for Cu-mediated inhibition of primary root elongation. Additional genetic and physiological data demonstrated that it was PINFORMED1 (PIN1), but not PIN2 or AUXIN1 (AUX1), that regulated this process. However, Cu-induced hydrogen peroxide accumulation did not contribute to Cu-induced auxin redistribution for inhibition of root elongation. When the possible role of ethylene in this process was analyzed, Cu had a similar impact on the root elongation of both the wild type and the ein2-1 mutant, implying that Cu-mediated inhibition of primary root elongation was not due to the ethylene signaling pathway.

Role of Ethylene and Its Cross Talk with Other Signaling Molecules in Plant Responses to Heavy Metal Stress

“…These data suggested that Al-induced ethylene production may lead to auxin redistribution by affecting auxin polar transport systems through AUX1 and PIN2 (Sun et al, 2010), which is an indicator of possible cross talk between ethylene and auxin in plant responses to HM stress. Interestingly, it was not PIN2 or AUX1 but PIN1 that was reported to be required for Cu-induced auxin redistribution in Arabidopsis (Yuan et al, 2013). Furthermore, the study of Yuan et al (2013) also showed that both ein2-1 and wild-type plants exhibited similar effects on the inhibition of primary root elongation under Cu stress, indicating that ethylenemediated signaling is not required for the Cu-inhibited primary root elongation.…”

Role of ROS and auxin in plant response to metal-mediated stress

“…8 The observed Cu-mediated auxin redistribution responsible for the inhibition of primary root elongation is mediated by PIN1, but not PIN2 or AUX1, different from Al-modulated auxin transport. 10,12,29 …”

“…36 Our recent studies also indicate that increased H 2 O 2 in Cu-treated seedlings does not contribute to Cu-regulated auxin redistribution for the inhibition of primary root elongation. 10 Thus, whether both ROS and auxin can crosstalk in plant response to different metal stresses needs to be further experimentally analyzed.…”

“…[4][5][6][7][8][9] Recent research has revealed that metal-mediated stress seems to have a direct impact on accumulation of relative oxygen species (ROS), content of nitric oxide (NO) and hormone levels in organs and the plants can quickly adjust their growth to harsh environment by influencing the cellular redox state and hormone signaling. [10][11][12][13][14][15][16] This review provides an update on the regulation of plant responses to metal-stress by ROS and auxin signaling pathway, primarily, with a focus on the copper, aluminum and cadmium stress. The mechanisms underlying how metal stress modulates the changes in auxin distribution and the network of ROS and auxin in plant response to metal stress are discussed based on recent studies.…”

Copper (Cu) stress affects carbon and antioxidant metabolism in Coffea arabica seedlings

“…Inhibition of cellular metabolic processes are observed in plants subjected to copper stress, which culminate in a reduction of biomass accumulation (Dey et al, 2014;Elleuch et al, 2013;Jouili and Ferjani, 2003). In addition, growth reduction due to the inadequate supply of copper results from several physiological changes such as mitotic disturbance (Bouazizi et al, 2010), decrease in auxin synthesis (Yuan et al, 2013), reduced photosynthetic activity (Droppa et al, 1987;Henriques, 1989) and lower carbohydrate synthesis (Yruela, 2009). At the end of the experiment, decrease in leaf biomass was also accompanied by a significant reduction of soluble sugars (Fig.…”