Plant chitinase responses to different metal-type stresses reveal specificity.

KEY MESSAGE: Chitinases in Glycine max roots specifically respond to different metal types and reveal a polymorphism that coincides with sensitivity to metal toxicity. Plants evolved various defense mechanisms to cope with metal toxicity. Chitinases (EC 3.2.1.14), belonging to so-called pathogenesis-related proteins, act as possible second line defense compounds in plants exposed to metals. In this work their activity was studied and compared in two selected soybean (Glycine max L.) cultivars, the metal-tolerant cv. Chernyatka and the sensitive cv. Kyivska 98. Roots were exposed to different metal(loid)s such as cadmium, arsenic and aluminum that are expected to cause toxicity in different ways. For comparison, a non-metal, NaCl, was applied as well. The results showed that the sensitivity of roots to different stressors coincides with the responsiveness of chitinases in total protein extracts. Moreover, detailed analyses of acidic and neutral proteins identified one polymorphic chitinase isoform that distinguishes between the two cultivars studied. This isoform was stress responsive and thus could reflect the evolutionary adaptation of soybean to environmental cues. Activities of the individual chitinases were dependent on metal type as well as the cultivar pointing to their more complex role in plant defense during this type of stress.

Defense responses of soybean roots during exposure to cadmium, excess of nitrogen supply and combinations of these stressors.

Heavy metal pollution is a serious environmental problem in agricultural soils since the uptake of heavy metals by plants represents an entry point into the food chain and is influenced by the form and amount of nitrogen (N) fertilization. Here we studied the defense responses in soybean roots exposed to ions of cadmium (applied as 50 mg l(-1) Cd(2+)) when combined with an excessive dose of N in form of NH(4)NO(3). Our data indicate that despite of stunted root growth, several stress symptoms typically observed upon cadmium treatment, e.g. peroxidation of lipid membranes or activation of chitinase isoforms, become suppressed at highly excessive N. At the same time, other defense mechanisms such as catalases and proline accumulation were elevated. Most importantly, the interplay of ongoing responses resulted in a decreased uptake of the metal into the root tissue. This report points to the complexity of plant defense responses under conditions of heavy metal pollution combined with intensive fertilization in agriculture.

Characterization of variable EST SSR markers for Norway spruce (Picea abies L.).

BACKGROUND: Norway spruce is widely distributed across Europe and the predominant tree of the Alpine region. Fast growth and the fact that timber can be harvested cost-effectively in relatively young populations define its status as one of the economically most important tree species of Northern Europe. In this study, EST derived simple sequence repeat (SSR) markers were developed for the assessment of putative functional diversity in Austrian Norway spruce stands. RESULTS: SSR sequences were identified by analyzing 14,022 publicly available EST sequences. Tri-nucleotide repeat motifs were most abundant in the data set followed by penta- and hexa-nucleotide repeats. Specific primer pairs were designed for sixty loci. Among these, 27 displayed polymorphism in a testing population of 16 P. abies individuals sampled across Austria and in an additional screening population of 96 P. abies individuals from two geographically distinct Austrian populations. Allele numbers per locus ranged from two to 17 with observed heterozygosity ranging from 0.075 to 0.99. CONCLUSIONS: We have characterized variable EST SSR markers for Norway spruce detected in expressed genes. Due to their moderate to high degree of variability in the two tested screening populations, these newly developed SSR markers are well suited for the analysis of stress related functional variation present in Norway spruce populations.

One dry summer: a leaf proteome study on the response of oak to drought exposure.

One of the most prominent hallmarks of the expected climate change in Europe is the higher prevalence of longer and more intense periods of summer drought. To preserve European oak forests, of considerable importance for European economical and ecological development, under these conditions knowledge on the mechanisms by which broad-leaved trees cope with drought is needed. In this study the effect of one season of drought stress, corresponding in length and soil water content to a dry summer, on young pedunculate oak trees (Quercus robur L.) was investigated by monitoring phenotypical parameters, the analysis of carbohydrate accumulation and a 2D-DIGE-based proteome study of leaves. In our experimental system, mimicking the conditions of a dry summer, the plants displayed reduced growth, moreover the transition through the developmental stages was affected. The data obtained during this study, supported by a separately published gene expression analysis study, indicated that the oak tried to adapt its metabolism in order to maintain its full molecular functionality. Initially the plants seemed to be able to cope with the imposed stress. However prolonged drought exposure overwhelmed the adaptive mechanisms and at the last sampling point of this study the molecular machinery succumbed.