Conditioning of roots with hypoxia increases aluminum and acid stress tolerance by mitigating activation of K+ efflux channels by ROS in barley: insights into cross-tolerance mechanisms
Ma, Y and Zhu, M and Shabala, L and Zhou, M and Shabala, S, Conditioning of roots with hypoxia increases aluminum and acid stress tolerance by mitigating activation of K+ efflux channels by ROS in barley: insights into cross-tolerance mechanisms, Plant and Cell Physiology, 57, (1) pp. 160-173. ISSN 0032-0781 (2016) [Refereed Article]
Copyright The Author 2015. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists. All rights reserved.
Aluminum (Al) is prevalent in soils, but Al toxicity is manifested only under acid conditions. It causes severe damages to
the root system. Short-term waterlogging stress can occur simultaneously with Al toxicity in areas with high rainfall or an
inappropriate irrigation pattern. Barley (Hordeum vulgare L.) is one of the most Al-sensitive small-grained cereals. In this work, we have investigated effects of short-term treatments
with hypoxia and phenolic acid (two major constraints in waterlogged soils) on root sensitivity to low-pH and Al stresses.
We showed that hypoxia-primed roots maintained higher cell viability when exposed to low-pH/Al stress, in both elongation
and mature root zones, and possessed superior ability to retain K+ in response to low-pH/Al stresses. These priming effects were not related to higher H+-ATPase activity and better membrane potential maintenance, and could not be explained by the increased expression levels
of HvHAK1, which mediates high-affinity K+ uptake in roots. Instead, hypoxia-conditioned roots were significantly less sensitive to H2O2 treatment, indicated by the 10-fold reduction in the magnitude of K+ efflux changes. This suggested that roots pre-treated with hypoxia desensitized reactive oxygen species (ROS)-inducible K+ efflux channels in root epidermis, most probably via enhanced antioxidative capacity. A possible role for Ca2+ in stress-induced ROS signaling pathways is also discussed. Overall, our results report, for the first time, the phenomenon
of cross-protection between hypoxia and low-pH/Al stresses, and causally link it to the cellís ability to maintain cytosolic
barley, Al tolerance, ROS, aluminum toxicity, calcium, cross-tolerance, hypoxia, potassium, reactive oxygen species