Unravelling the response of poplar (Populus nigra) roots to mechanical stress imposed by bending

Abstract

Mechanical stress is a widespread environmental condition that can be caused by several factors (i.e. gravity, touch, wind, soil density, soil compaction and grazing, slope) and that can severely affect plant stability. In response to mechanical stress and to improve their anchorage, plants have developed complex mechanisms to detect mechanical perturbation and to induce a suite of modifications at anatomical, physiological, biochemical, biophysical and molecular level. Although it is well recognized that one of the primary functions of root systems is to anchor the plant to the soil, root response to mechanical stresses have been investigated mainly at morphological and biomechanical level, whereas investigations about the molecular mechanisms underlying these important alterations are still in an initial stage. We have used an experimental system in which the taproot poplar seedlings are bent to simulate mechanical perturbation to begin investigate the mechanisms involved in root response to mechanical stress. The results reported herein show that, in response to bending, the poplar root changes its morphology by emitting new lateral roots, and its biomechanical properties by increasing the root biomass and lignin synthesis. In addition, using a proteomic approach, we found that several proteins involved in the signal transduction pathway, detoxification and metabolism are up-regulated and/or down-regulated in the bent root. These results provide new insight into the obscure field of woody root response to mechanical stress, and can serve as a basis for future investigations aimed at unravelling the complex mechanism involved in the reaction of root biology to environmental stress.

MicroRNAs expression patterns in the response of poplar woody root to bending stress

“…One-year-old Populus nigra seedlings (Alasia Franco Vivai, Savigliano (CN), Italy; http://www.alasiafranco.it/) were subjected to mechanical stress by bending their taproots around a 90°angle curved steel net, as described in our previous studies (Scippa et al 2008;Trupiano et al 2012b). Thirty plants with bent roots, together with the same number of plants with taproots linked to a vertical steel net (control, C), were grown under controlled water regime and natural photoperiod and temperature.…”

“…In woody plants, on the other hand, root response to mechanical stresses has been mostly investigated at the morphological, biomechanical and anatomical level, whereas studies focused on molecular mechanisms are still scarce. In a previous work, we used a right-angle curved steel net to induce a long-term mechanical stress response in woody taproot of poplar (Populus nigra L.) and found that different intensity of tension and compression forces and the direction of gravity can elicit specific responses such as lateral roots emission and reaction wood formation (Scippa et al 2008;Trupiano et al 2012aTrupiano et al , b, 2014. Furthermore, using this experimental system we analyzed spatial and temporal changes in the root proteome and in hormone levels (Trupiano et al 2012b(Trupiano et al , 2014.…”

The biogeomorphological life cycle of poplars during the fluvial biogeomorphological succession: a special focus on Populus nigra L.

“…from branches, broken and partly buried trunks, excavated roots). Recent proteomic analyses have shown that poplars have developed complex biochemical mechanisms to detect mechanical constraints such as those imposed by water flow and sediment burial and to induce specific responses improving their anchorage (Scippa et al, 2008;Trupiano et al, 2012). Vegetative propagation represents a defense mechanism to mechanical constraints, submersion and sediment burial.…”

“…Chemical ecology or ecological stoichiometry (Sterner and Elser, 2002) and metagenomics (Marco, 2010) may also become useful in the near future to identify respectively characteristic chemical (e.g. Many of these trait loci have already been mapped (Yin et al, 2004), for example, those related to the response of poplar roots to mechanical stress imposed by bending (Scippa et al, 2008;Trupiano et al, 2012). At the molecular level, the role of intraspecific genetic variability of P. nigra populations related to engineer traits must be defined in order to quantify the variability in abiotic responses (e.g.…”

Shaping the multifunctional tree: the use of Salicaceae in environmental restoration

“…In particular, proteins with altered synthesis due to changes in gene expression may be used to design molecular markers for the selection of genotypes (Kieffer et al 2009, Regier et al 2009, Visioli et al 2010). However, Scippa et al (2008) have studied the complex mechanism involved in the reaction of root biology to environmental stress. In particular, Trupiano et al (2012a) have observed functional and structural changes in roots, which emitted new laterals and increased biomass and lignin synthesis under mechanical stress.…”