Szabolcs Rudnóy

Tests of species concepts of the small, white, European group of Tuber spp. based on morphology and rDNA ITS sequences with special reference to Tuber rapaeodorum

Several taxonomic problems arise in the group of small, white European truffles, probably due to the over-emphasized significance of certain morphological features of ascomata. The distinction between Tuber rapaeodorum Tul. & C. Tul. and Tuber borchii Vittad. and Tuber puberulum Berk. & Broome has not been accepted in several recent studies. Furthermore, the existence of T. rapaeodorum been questioned in some recent synopses of the genus. We conducted microscopic and ITS sequence investigations of 31 herbarium specimens. Using morphological features such as peridium structure, form and size of spores and dermatocystidia and spore numbers per ascus, we could distinguish T. borchii, T. foetidum Vittad., T. maculatum Vittad., Tuber puberulum, and T. rapaeodorum. Analysis of whole ITS sequences showed sharp differences among the morphologically separated groups. Neighbour-joining and parsimony methods produced highly supported branches and confirmed the identity of these species.

Changes in the Content of Modified Nucleotides in Wheat rRNA during Greening

The modified nucleotide content of the ribosomal RNAs in wheat is greatly influenced by light. The rRNAs of etiolated seedlings contain far fewer modified derivatives. The modified nucleotide composition characteristic of green plants develops gradually as a result of irradiation. In the course of the experiments changes in the state of modification of 5.8S and 18S rRNAs were examined during the greening of etiolated wheat seedlings. Three types of minor nucleotides, O2′-methyladenosine, O2′-methylguanosine and pseudouridine were found in the 5.8S rRNA of green wheat leaves, none of which was detected in etiolated wheat. The minor nucleotides appeared in the 5.8S rRNA only after 48 h irradiation. The sequences of 5.8S rDNA, TTS1, ITS2 and 18S rDNA were also determined and the presence of the hyper-modified nucleotide 1-methyl-3-(α-amino-α-carboxypropyl)-pseudouridine was detected in green wheat 18S rRNA. This minor component was not demonstrable in etiolated wheat 18S rRNA, but appeared after irradiation for 48 h.

Species Delimitation in Taxonomically Difficult Fungi: The Case of Hymenogaster

Background False truffles are ecologically important as mycorrhizal partners of trees and evolutionarily highly interesting as the result of a shift from epigeous mushroom-like to underground fruiting bodies. Since its first description by Vittadini in 1831, inappropriate species concepts in the highly diverse false truffle genus Hymenogaster has led to continued confusion, caused by a large variety of prevailing taxonomical opinions. Methodology In this study, we reconsidered the species delimitations in Hymenogaster based on a comprehensive collection of Central European taxa comprising more than 140 fruiting bodies from 20 years of field work. The ITS rDNA sequence dataset was subjected to phylogenetic analysis as well as clustering optimization using OPTSIL software. Conclusions Among distinct species concepts from the literature used to create reference partitions for clustering optimization, the broadest concept resulted in the highest agreement with the ITS data. Our results indicate a highly variable morphology of H. citrinus and H. griseus, most likely linked to environmental influences on the phenology (maturity, habitat, soil type and growing season). In particular, taxa described in the 19th century frequently appear as conspecific. Conversely, H. niveus appears as species complex comprising seven cryptic species with almost identical macro- and micromorphology. H. intermedius and H. huthii are described as novel species, each of which with a distinct morphology intermediate between two species complexes. A revised taxonomy for one of the most taxonomically difficult genera of Basidiomycetes is proposed, including an updated identification key. The (semi-)automated selection among species concepts used here is of importance for the revision of taxonomically problematic organism groups in general.

S-methylmethionine alleviates the cold stress by protection of the photosynthetic apparatus and stimulation of the phenylpropanoid pathway

Maize (Zea mays L.) seedlings were pretreated with 0.001 g dm−3 S-methylmethionine (SMM) in the nutrient solution for 24 h and then subjected to chilling (6 °C for 2, 4, 6, 10, and 24 h). Cold stress significantly decreased the maximum quantum yield of photosystem II (variable to maximum chlorophyll fluorescence ratio, Fv/Fm) during the whole experiment but SMM pretreatment significantly reduced this decline. Content of phenolics and anthocyanins increased in response to low temperature, and SMM pretreatment further intensified the synthesis of these protective agents. These findings were supported by increased expression of genes coding enzymes of the phenylpropanoid pathway leading to synthesis of cinnamate-4-hydroxylase (C4H) and chalcone-synthase (CHS). Our results indicate that SMM pretreatment alleviates the low temperature stress by reducing the damage of the photosynthetic apparatus and stimulating the phenylpropanoid pathway.

Intraspecific invariability of the internal transcribed spacer region of rDNA of the truffle Terfezia terfezioides in Europe

ITS regions (internal transcribed spacers—ITS1 andITS2—with the 5.8S gene of the nuclear rDNA) of 25 fruit body samples ofTerfezia terfezioides, originating from Hungary and Italy, were compared. The amplification and sequencing of the ITS region was successful with both theITS1-ITS4 andITSIF-ITS4 primer pairs. No differences of the restriction fragment length polymorphism profiles were detected among 19 samples collected in one place at the same time. The sequences of the ITS region of 9 samples collected in different localities were highly invariable, differing in only two bases. Thus the intraspecific homogeneity of the ITS region seems to be an important species-specific characteristic ofT. terfezioides in contrast to otherTerfezia species. As the samples of the species were collected from different and distant localities of Europe, the ITS sequence ofT. terfezioides can be considered a very conservative, reliable molecular marker of the fungus. *** DIRECT SUPPORT *** A00EN076 00008

S -methylmethionine contributes to enhanced defense against Maize dwarf mosaic virus infection in maize

The beneficial and protective effects of S-methylmethionine (SMM) were investigated in Maize dwarf mosaic virus (MDMV) infected maize (Zea mays L.). Response reactions and alterations in the physiological state of the plants were monitored by following changes in the values of chlorophyll a fluorescence and chlorophyll content, and differences in the expression patterns of the stress-related genes S-adenosylmethionine synthase (SAMS) and the 14-3-3-like protein gene G-box factor 14-6 (GF14-6). Infection was validated using the ELISA technique. A pronounced decrease in the red to far-red chlorophyll a fluorescence ratio, indicative of chlorophyll content, was observed in infected plants, which was tempered by SMM pretreatment. A noticeable decrease in the photochemical quenching of photosystem II and the thermal dissipation of the antennae was observed, together with a notable increase in other non-photochemical energy dissipation parameters in response to MDMV infection. SMM treatment enhanced blue fluorescence in both uninfected and MDMV-infected plants (probably due to the production of protective phenolic compounds), while infection characteristically increased green fluorescence emission. SMM treatment was found to elevate the rate of gene expressions of SAMS and GF14-6. The results suggest that SMM pretreatment enhances the stress response reactions that protect maize plants against MDMV infection.

Interactions of S-methylmethionine and UV-B can modify the defence mechanisms induced in maize

We examined the interactions of an exogenously added non-proteinogenic amino acid, S-methylmethionine (SMM) and UV-B radiation in young maize plants. We observed that exposure to UV-B light caused a substantial increase in both the phenolics and anthocyanin contents. Pretreatment with SMM also induced a slight, but statistically significant increase in the total phenol content, and was also able to accelerate the rise in the UV-B-induced anthocyanin level. Gene expression patterns indicated that the general phenylpropanoid pathway was most strongly induced by the combined effect of SMM and UV, while the anthocyanin synthesis by the sole UV-B treatment. SMM treatment and UV-B light led to a substantial increase in the activities of the antioxidant enzymes catalase (CAT), ascorbate peroxidase (APX) and glutathione S-transferase and SMM pretreatment always enhanced the effect of UV-B. While the activity of CAT showed a significant increase in UV-B- and/or SMM-treated plants, APX was stimulated only by SMM. The present results suggest that the protective mechanisms induced by UV-B radiation could be enhanced by SMM treatment and reinforce the earlier observations of priming effects of SMM so that it can contribute to our knowledge about the SMM-induced protection against various types of stressors.

S-Methylmethionine-Salicylate Pretreatment Reduces Low Temperature Stress in Maize

Low temperature is one of the major environmental stressors affecting cultivated plants, damaging metabolic processes and cell structures. Due to its tropical origin maize (Zea mays L.) is particularly sensitive to chilling stress. The present study aimed to ascertain whether the amino acid derivative S-methylmethionine-salicylate (MMS) is effective in reducing cold stress injury in maize. In order to obtain more detailed information on the effect of MMS, changes were examined at the physiological, gene expression and metabolic levels. MMS pretreatment helped to preserve the photosynthetic activity, enhanced the expression of certain genes in the phenylpropanoid pathway and was measured higher anthocyanin content in the stalk. The results show that MMS pretreatment could reduce the damage caused by low temperature in maize.

The effects of putrescine are partly overlapping with osmotic stress processes in wheat

Polyamine metabolism is in relation with several metabolic pathways and linked with plant hormones or signalling molecules; in addition polyamines may modulate the up- or down-regulation of gene expression. However the precise mechanism by which polyamines act at the transcription level is still unclear. In the present study the modifying effect of putrescine pre-treatment has been investigated using the microarray transcriptome profile analysis under the conditions where exogenous putrescine alleviated osmotic stress in wheat plants. Pre-treatment with putrescine induced the unique expression of various general stress-related genes. Although there were obvious differences between the effects of putrescine and polyethylene glycol treatments, there was also a remarkable overlap between the effects of putrescine and osmotic stress responses in wheat plants, suggesting that putrescine has already induced acclimation processes under control conditions. The fatty acid composition in certain lipid fractions and the antioxidant enzyme activities have also been specifically changed under osmotic stress conditions or after treatment with putrescine.

Janus-faced nature of light in the cold acclimation processes of maize

Exposure of plants to low temperature in the light may induce photoinhibitory stress symptoms, including oxidative damage. However, it is also known that light is a critical factor for the development of frost hardiness in cold tolerant plants. In the present work the effects of light during the cold acclimation period were studied in chilling-sensitive maize plants. Before exposure to chilling temperature at 5°C, plants were cold acclimated at non-lethal temperature (15°C) under different light conditions. Although exposure to relatively high light intensities during cold acclimation caused various stress symptoms, it also enhanced the effectiveness of acclimation processes to a subsequent severe cold stress. It seems that the photoinhibition induced by low temperature is a necessary evil for cold acclimation processes in plants. Greater accumulations of soluble sugars were also detected during hardening at relatively high light intensity. Certain stress responses were light-dependent not only in the leaves, but also in the roots. The comparison of the gene expression profiles based on a microarray study demonstrated that the light intensity is at least as important a factor as the temperature during the cold acclimation period. Differentially expressed genes were mainly involved in most of assimilation and metabolic pathways, namely photosynthetic light capture via the modification of chlorophyll biosynthesis and the dark reactions, carboxylic acid metabolism, cellular amino acid, porphyrin or glutathione metabolic processes, ribosome biogenesis and translation. Results revealed complex regulation mechanisms and interactions between cold and light signalling processes.