ORIGINAL ARTICLE The fatal effect of tungsten on Pisum sativum L. root cells: indications for endoplasmic reticulum stress-induced programmed cell death Ioannis-Dimosthenis S. Adamakis • Emmanuel Panteris • Eleftherios P. Eleftheriou Received: 22 December 2010 / Accepted: 25 January 2011 / Published online: 23 February 2011 Ó Springer-Verlag 2011 Abstract Programmed cell death (PCD) is a widespread response of plants against abiotic stress, such as heavy metal toxicity. Tungsten (W) is increasingly considered toxic for plants since it irreversibly affects their growth. Therefore, we investigated whether W could induce some kind of PCD in plants, like other heavy metals do. The morphology of cell and nucleus, the integrity of the cyto- skeleton, Evans Blue absorbance and the expression of PCD-related genes were used as indicators of PCD in W-treated roots of Pisum sativum (pea). TEM and fluo- rescence microscopy revealed mitotic cycle arrest, proto- plast shrinkage, disruption of the cytoskeleton and chromatin condensation and peripheral distribution in the nucleus of W-affected cells. Moreover, Evans Blue absorbance in roots increased in relation to the duration of W treatment. These effects were suppressed by inhibitors of the 26S proteasome, caspases and endoplasmic reticu- lum stress. In addition, silencing of DAD-1 and induction of HSR203J, BiP-D, bZIP28 and bZIP60 genes were also recorded in W-treated pea roots by semi-quantitative RT- PCR. The above observations show that W induces a kind of PCD in pea roots, further substantiating its toxicity for plants. Data imply that endoplasmic reticulum stress- unfolded protein response may be involved in W-induced PCD. Keywords 26S proteasome Á Caspase-like proteases Á Endoplasmic reticulum stress (ER stress) Á Microtubules Á Programmed cell death (PCD) Á Tungsten (W) Á Unfolded protein response (UPR) Abbreviations ER Endoplasmic reticulum ERAD ER associated degradation PCD Programmed cell death PBA 4-Phenylbutyric acid UPR Unfolded protein response Introduction Several metals have been proven to be toxic for plants. One of the responses of plants to such toxicity is the execution of programmed cell death (PCD). For example, this was shown for cadmium (Iakimova et al. 2008; Kuthanova et al. 2008) and aluminium (Pan et al. 2001; Tamas et al. 2005). Tungsten (W) is a scarce heavy metal in nature, but it is locally accumulated at high concentrations as a waste of mines, industries, agricultural and military activities (Wilson and Pyatt 2006; Clausen and Korte 2009 and references therein). Over the last decade, W has attracted the attention of scientists, since it was shown to be toxic for living organisms (Koutsospyros et al. 2006; Steinberg et al. 2007). In particular, Koutsospyros et al. (2006) stated: ‘‘…it appears that environmental obscurity for tungsten and its compounds has ended and environmental scrutiny has emerged’’. Tungsten toxicity in plants has been initially related to the competition with its chemical relative, molybdenum (Mo), since it binds to molybdoenzymes and inactivates Electronic supplementary material The online version of this article (doi:10.1007/s00425-011-1372-5) contains supplementary material, which is available to authorized users. I.-D. S. Adamakis (&) Á E. Panteris (&) Á E. P. Eleftheriou Department of Botany, School of Biology, Aristotle University of Thessaloniki, 541 24 Thessaloniki, Macedonia, Greece e-mail: iadamaki@bio.auth.gr E. Panteris e-mail: epanter@bio.auth.gr 123 Planta (2011) 234:21–34 DOI 10.1007/s00425-011-1372-5