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4 Acta Physiologiae Plantarum

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Expression of defence-related peroxidases Prx7 and Prx8 during abiotic stresses in barley roots

100%

Tamas L. , Durcekova K. , Huttova J. , Mistrik I.

tom 31

nr 1

The expression of defence-related peroxidases Prx7 and Prx8 in barley roots grown under selected abiotic stress conditions (toxic metals: Cd, Al, Co, Cu, Hg; drought, salinity, extreme temperatures: heat, cold) and compounds activating (2,4-D) or inhibiting (SHAM) POD activity as well as H₂O₂ and H₂O₂ scavenger (DTT) was characterized. Strong Cd concentration dependent expression of Prx8 peroxidase gene was observed, which correlated with root growth inhibition induced by Cd-and some other stress factors (heavy metals, heat and salinity). Application of H₂O₂ did not cause changes in expression of Prx8, but H₂O₂ scavenger (DTT) as well as the inhibitor (SHAM) and the activator (2,4-D) of PODs induced increase in Prx8 expression. Our results demonstrate that root growth inhibition during any disturbance of active oxygen species (AOS) in root tissue is correlated with upregulation of Prx8 gene expression in barley roots.

Cadmium disrupts apoplastic ascorbate redox status in barley root tips

100%

Bocova B. , Mistrik I. , Pavlovkin J. , Tamas L.

nr 6

Using a short-term Cd treatment (5–30 min), we analysed the effect of Cd on apoplastic ascorbate redox status and their regeneration during the recovery period in barley root tips. Root growth inhibition induced by 15 µM Cd was detectable after 5 min of exposure and increased in a time-dependent manner up to 15 min of exposure. High 30 µM Cd concentration completely inhibited root growth during the first 6 h after short-term treatment. In parallel with Cd-induced root growth inhibition, a rapid decrease of apoplastic ascorbate dehydroascorbate ratio was observed immediately after short-term treatments. During the recovery from 15 µM Cd short-term treatment, apoplastic ascorbate was rapidly regenerated to the control level in the first root segment containing meristem and elongation zone. In contrast to 15 µM Cd treatment, in 30 µM Cd-treated roots apoplastic ascorbate level was sustained at a significantly lower level compared to control roots. We confirmed that a decrease of apoplastic ascorbate/dehydroascorbate ratio in the elongation zone was associated with root growth inhibition or arrest.

The effect of aluminium on polypeptide pattern of cell wall proteins isolated from the roots of Al-sensitive and Al-resistant barley cultivars

100%

Tamas L. , Huttova J. , Hajasova L. , Mistrik I.

nr 2

Primary stress response induced by different elements is mediated through auxin signalling in barley root tip

75%

Zelinova V. , Alemayehu A. , Bocova B. , Huttova J. , Mistrik I. , Tamas L.

nr 11

Short-term exposure (15 min) of barley roots to different chemical elements revealed that Cd, Cu, Hg and Pb were the most toxic ones causing a marked root growth inhibition even at µM concentrations. Gd, La, Al, Cr, As, Zn, Ni and Se inhibited root growth to a similar extent only at mM concentrations. Despite the high 20 mM concentration, Co caused only a slight, while Mn, Mg or Ca did not evoke any root growth inhibition. Elements at concentrations inhibiting root growth caused a considerable accumulation of indole-3-acetic acid in the root apex. While Cr, As and Zn inhibited, Cd, Cu, Hg, Pb, Gd, La and Al markedly stimulated the generation of reactive oxygen species in the beginning of differentiation zone. Auxin signalling inhibitor alleviated or prevented root growth inhibition, reactive oxygen species generation and the stimulation of lipoxygenase and glutathione peroxidase activity by various elements, indicating a key role of auxin signalling in the stress response of barley root tip. On the other hand, it did not affect or even had an additive effect on dehydroascorbate reductase and ascorbic acid oxidase activity in combination with different elements. Our results indicate that the primary response of barley roots to the presence of various chemical elements during the shortterm treatment is not a specific but rather a general adaptive stress response enabling the plant to survive adverse conditions.