Moderate salt treatment alleviates ultraviolet-B radiation caused impairment in poplar plants.

Xuan Ma,Stanley Lutts,Yang Wang,Yong-Feng Gao,Yong-Bin Ou,Yin-An Yao,Yu-Fang Sun,Yong-Fu Chen,Tao-Tao Li

doi:10.1038/srep32890

Abstract

The effects of moderate salinity on the responses of woody plants to UV-B radiation were investigated using two Populus species (Populus alba and Populus russkii). Under UV-B radiation, moderate salinity reduced the oxidation pressure in both species, as indicated by lower levels of cellular H2O2 and membrane peroxidation, and weakened the inhibition of photochemical efficiency expressed by O-J-I-P changes. UV-B-induced DNA lesions in chloroplast and nucleus were alleviated by salinity, which could be explained by the higher expression levels of DNA repair system genes under UV-B&salt condition, such as the PHR, DDB2, and MutSα genes. The salt-induced increase in organic osmolytes proline and glycine betaine, afforded more efficient protection against UV-B radiation. Therefore moderate salinity induced cross-tolerance to UV-B stress in poplar plants. It is thus suggested that woody plants growing in moderate salted condition would be less affected by enhanced UV-B radiation than plants growing in the absence of salt. Our results also showed that UV-B signal genes in poplar plants PaCOP1, PaSTO and PaSTH2 were quickly responding to UV-B radiation, but not to salt. The transcripts of PaHY5 and its downstream pathway genes (PaCHS1, PaCHS4, PaFLS1 and PaFLS2) were differently up-regulated by these treatments, but the flavonoid compounds were not involved in the cross-tolerance since their concentration increased to the same extent in both UV-B and combined stresses.

Highlights

The effects of moderate salinity on the responses of woody plants to ultraviolet-B radiation (UV-B) radiation were investigated using two Populus species (Populus alba and Populus russkii)
Plants can synthesize protective proteins and antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX), to protect cell against the various damages induced by reactive oxygen species (ROS) which are commonly overproduced under stress conditions
Distinct O-J-I-P changes were observed between control and UV-B in the shape of the O-J-I-P transient for both P. alba (Fig. 1a) and P. russkii (Fig. 1b)

Summary

Introduction

The effects of moderate salinity on the responses of woody plants to UV-B radiation were investigated using two Populus species (Populus alba and Populus russkii). Moderate salinity induced cross-tolerance to UV-B stress in poplar plants. In numerous semi-arid or arid regions, forest ecosystems suffer from moderate salt stress Salinity may cause both osmotic and ionic stresses to plants. Plants have evolved many strategies to alleviate salinity stress They are able to perform osmotic adjustment through the accumulation of osmolytes, such as proline, glycine betaine, and oligosaccharides[2] in order to maintain water absorption. Puniran-Hartley et al.[21] observed that salt pretreatment improved UV-B tolerance in wheat and barley These studies confirm interaction effects between UV-B radiation and osmotic or ion stresses but data remain contradictories

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