Effect of salt stress on prenol lipids in the leaves of Tilia ‘Euchlora’

Soil contamination caused by the NaCl used to de-ice slippery roads in winter is now recognized as one of the major causes of nutrient disorders and death in urban trees. It is believed that polyisoprenoids may have a specific role in the adaptation of plants to adverse conditions and habitats; it is further believed that in the cell, they may exhibit a protective effect in response to biotic and abiotic stress. The aim of this study was to evaluate the effect of salt stress on the content of prenol lipids in the leaves of Crimean linden (Tilia ‘Euchlora’). The Cl content in the slightly damaged (“healthy”) leaves averaged 0.96%, while that in the heavily damaged (“sick”) leaves averaged 2.02%. The leaves of control trees contained on average 0.57% Cl. The Na contents in the healthy and damaged leaves were 208 mg/kg and 1038 mg/kg, respectively, and the Na content in the control areas was 63 mg/kg. A mixture of polyprenols consisting of four compounds, prenol-9, prenol-10, prenol-11 and prenol-12, was identified in the leaves of Crimean linden. This mixture was dominated by prenol-10 (2.16–6.90 mg/g). The polyprenol content was highest in the leaves of “healthy” trees (approximately 13.31 mg/g), was lower in the case of “sick” trees (approximately 9.18 mg/g), and was the lowest in the control trees (mean 4.71 mg/g). No changes were observed in the composition of the mixture of polyprenols under these conditions. The results suggest that polyprenols may affect the accumulation of Cl in leaves. This phenomenon is evidenced by the high content of prenols in the leaves of trees considered “healthy” but growing under conditions of increased soil salinity and the lower content of prenols in the leaves of the “sick” and control trees. It is advisable to further investigate the role of prenol lipids in the leaves of trees subjected to salt stress. BACZEWSKA A., DMUCHOWSKI W., JÓŹWIAK A., GOZDOWSKI D., BRĄGOSZEWSKA P., DĄBROWSKI P., ŚWIEŻEWSKA E

Quantitative and qualitative characteristics of cell wall components and prenyl lipids in the leaves of Tilia x euchlora trees growing under salt stress

The study was focused on assessing the presence of arabinogalactan proteins (AGPs) and pectins within the cell walls as well as prenyl lipids, sodium and chlorine content in leaves of Tilia x euchlora trees. The leaves that were analyzed were collected from trees with and without signs of damage that were all growing in the same salt stress conditions. The reason for undertaking these investigations was the observations over many years that indicated that there are trees that present a healthy appearance and trees that have visible symptoms of decay in the same habitat. Leaf samples were collected from trees growing in the median strip between roadways that have been intensively salted during the winter season for many years. The sodium content was determined using atomic spectrophotometry, chloride using potentiometric titration and poly-isoprenoids using HPLC/UV. AGPs and pectins were determined using immunohistochemistry methods. The immunohistochemical analysis showed that rhamnogalacturonans I (RG-I) and homogalacturonans were differentially distributed in leaves from healthy trees in contrast to leaves from injured trees. In the case of AGPs, the most visible difference was the presence of the JIM16 epitope. Chemical analyses of sodium and chloride showed that in the leaves from injured trees, the level of these ions was higher than in the leaves from healthy trees. Based on chromatographic analysis, four polyisoprenoid alcohols were identified in the leaves of T. x euchlora. The levels of these lipids were higher in the leaves from healthy trees. The results suggest that the differences that were detected in the apoplast and symplasm may be part of the defensive strategy of T. x euchlora trees to salt stress, which rely on changes in the chemical composition of the cell wall with respect to the pectic and AGP epitopes and an increased synthesis of prenyl lipids

Selective sweeps identification in distinct groups of cultivated rye (Secale cereale L.) germplasm provides potential candidate genes for crop improvement

Background: During domestication and subsequent improvement plants were subjected to intensive positive selection for desirable traits. Identification of selection targets is important with respect to the future targeted broadening of diversity in breeding programmes. Rye (Secale cereale L.) is a cereal that is closely related to wheat, and it is an important crop in Central, Eastern and Northern Europe. The aim of the study was (i) to identify diverse groups of rye accessions based on high-density, genome-wide analysis of genetic diversity within a set of 478 rye accessions, covering a full spectrum of diversity within the genus, from wild accessions to inbred lines used in hybrid breeding, and (ii) to identify selective sweeps in the established groups of cultivated rye germplasm and putative candidate genes targeted by selection.Results: Population structure and genetic diversity analyses based on high-quality SNP (DArTseq) markers revealed the presence of three complexes in the Secale genus: S. sylvestre, S. strictum and S. cereale/vavilovii, a relatively narrow diversity of S. sylvestre, very high diversity of S. strictum, and signatures of strong positive selection in S. vavilovii. Within cultivated ryes we detected the presence of genetic clusters and the influence of improvement status on the clustering. Rye landraces represent a reservoir of variation for breeding, and especially a distinct group of landraces from Turkey should be of special interest as a source of untapped variation. Selective sweep detection in cultivated accessions identified 133 outlier positions within 13 sweep regions and 170 putative candidate genes related, among others, to response to various environmental stimuli (such as pathogens, drought, cold), plant fertility and reproduction (pollen sperm cell differentiation, pollen maturation, pollen tube growth), and plant growth and biomass production.Conclusions: Our study provides valuable information for efficient management of rye germplasm collections, which can help to ensure proper safeguarding of their genetic potential and provides numerous novel candidate genes targeted by selection in cultivated rye for further functional characterisation and allelic diversity studies

Effect of salt stress in urban conditions on two Acer species with different sensitivity

Background. The benefits of trees in urban areas include the following: an increase in ecosystem health, an increase in human health, the mitigation of the effects of heat and drought at microclimate level, the storage and sequestration of carbon, and a reduction in air pollution and noise. These ecosystem services can be provided only by trees that are in good health. The main cause of salt stress in urban environments is the use of deicing salts on the streets in winter. Salt stress is a complex process that includes changes in plants on the physiological, histological, cellular and molecular levels, leading to limitations in nutrient uptake, disrupting the ionic balance of trees and resulting in the death of roadside trees. In response to salinity, trees have developed a variety of defence mechanisms that allow them to minimize the effects of stress and maintain homeostasis. Methodology. The reactions of two species Acer species: A. platanoides and A. campestre, which have different sensitivities to the unfavourable conditions of the urban environments (mainly salt stress), were investigated. The research included two experiments: a field experiment with city trees and a controlled pot experiment with young trees treated with increasing doses of salt. In both experiments, the following were performed: an assessment of the health condition of the trees and the content of macroelements as well as the Cl and Na in leaves and a qualitative and quantitative analysis of polyprenols. Results. A. campestre had a more specific strategy than A. platanoides for dealing with Na and Cl, which resulted in undamaged leaves. Under the same conditions, A. platanoides leaves contained more Cl and Na and were severely damaged. The disruption of the ion balance due to salt stress was lower in A. campestre than in A. platanoides. Compared with A. platanoides, A. campestre synthesized more polyprenols in the field experiment. This ability was acquired during the process of acclimation, because it occurred only in the mature trees in the field experiment and not in the young trees in the pot experiment. Conclusions. The use of two experimental methods (i.e., the field and pot experiments) allowed for a more complete assessment of tree strategies to mitigate salt stress. A. campestre displayed a more specific strategy than A. platanoides. This strategy was based on several elements. A. campestre limited Cl and Na transport to the leaves, which resulted in a lack of damage to those organs. Under the same conditions, A. platanoides individuals contained more Cl and Na in their leaves and were seriously damaged. A. campestre synthesized larger amounts of polyprenols, which probably have the ability to mitigate salt stress. This ability was acquired during the process of acclimation, because it occurred only in the mature trees in the field experiment and was not observed in the young trees in the pot experiment

DArT Markers Effectively Target Gene Space in the Rye Genome

Large genome size and complexity hamper considerably the genomics research in relevant species. Rye (Secale cereale L.) has one of the largest genomes among cereal crops and repetitive sequences account for over 90% of its length. Diversity Arrays Technology is a high-throughput genotyping method, in which a preferential sampling of gene-rich regions is achieved through the use of methylation sensitive restriction enzymes. We obtained sequences of 6,177 rye DArT markers and following a redundancy analysis assembled them into 3,737 non-redundant sequences, which were then used in homology searches against five Pooideae sequence sets. In total 515 DArT sequences could be incorporated into publicly available rye genome zippers providing a starting point for the integration of DArT- and transcript-based genomics resources in rye. Using Blast2Go pipeline we attributed putative gene functions to 1101 (29.4%) of the non-redundant DArT marker sequences, including 132 sequences with putative disease resistance-related functions, which were found to be preferentially located in the 4RL and 6RL chromosomes. Comparative analysis based on the DArT sequences revealed obvious inconsistencies between two recently published high density consensus maps of rye. Furthermore we demonstrated that DArT marker sequences can be a source of SSR polymorphisms. Obtained data demonstrate that DArT markers effectively target gene space in the large, complex, and repetitive rye genome. Through the annotation of putative gene functions and the alignment of DArT sequences relative to reference genomes we obtained information, that will complement the results of the studies, where DArT genotyping was deployed, by simplifying the gene ontology and microcolinearity based identification of candidate genes

Chromosome-scale genome assembly provides insights into rye biology, evolution and agronomic potential

Rye (Secale cereale L.) is an exceptionally climate-resilient cereal crop, used extensively to produce improved wheat varieties via introgressive hybridization and possessing the entire repertoire of genes necessary to enable hybrid breeding. Rye is allogamous and only recently domesticated, thus giving cultivated ryes access to a diverse and exploitable wild gene pool. To further enhance the agronomic potential of rye, we produced a chromosome-scale annotated assembly of the 7.9-gigabase rye genome and extensively validated its quality by using a suite of molecular genetic resources. We demonstrate applications of this resource with a broad range of investigations. We present findings on cultivated rye's incomplete genetic isolation from wild relatives, mechanisms of genome structural evolution, pathogen resistance, low-temperature tolerance, fertility control systems for hybrid breeding and the yield benefits of rye-wheat introgressions.Peer reviewe

Detection of segregation distortion loci in triticale (x Triticosecale Wittmack) based on a high-density DArT marker consensus genetic linkage map

<p>Abstract</p> <p>Background</p> <p>Triticale is adapted to a wide range of abiotic stress conditions, is an important high-quality feed stock and produces similar grain yield but more biomass compared to other crops. Modern genomic approaches aimed at enhancing breeding progress in cereals require high-quality genetic linkage maps. Consensus maps are genetic maps that are created by a joint analysis of the data from several segregating populations and different approaches are available for their construction. The phenomenon that alleles at a locus deviate from the Mendelian expectation has been defined as segregation distortion. The study of segregation distortion is of particular interest in doubled haploid (DH) populations due to the selection pressure exerted on the plants during the process of their establishment.</p> <p>Results</p> <p>The final consensus map, constructed out of six segregating populations derived from nine parental lines, incorporated 2555 DArT markers mapped to 2602 loci (1929 unique). The map spanned 2309.9 cM with an average number of 123.9 loci per chromosome and an average marker density of one unique locus every 1.2 cM. The R genome showed the highest marker coverage followed by the B genome and the A genome. In general, locus order was well maintained between the consensus linkage map and the component maps. However, we observed several groups of loci for which the colinearity was slightly uneven. Among the 2602 loci mapped on the consensus map, 886 showed distorted segregation in at least one of the individual mapping populations. In several DH populations derived by androgenesis, we found chromosomes (2B, 3B, 1R, 2R, 4R and 7R) containing regions where markers exhibited a distorted segregation pattern. In addition, we observed evidence for segregation distortion between pairs of loci caused either by a predominance of parental or recombinant genotypes.</p> <p>Conclusions</p> <p>We have constructed a reliable, high-density DArT marker consensus genetic linkage map as a basis for genomic approaches in triticale research and breeding, for example for multiple-line cross QTL mapping experiments. The results of our study exemplify the tremendous impact of different DH production techniques on allele frequencies and segregation distortion covering whole chromosomes.</p

Association analysis of low-phosphorus tolerance in West African pearl millet using DArT markers

Pearl millet [Pennisetum glaucum (L.) R. Br.] is a food security crop in the harshest agricultural regions of the world. While low soil phosphorus (P) availability is a big constraint on its production, especially in West Africa (WA), information on genomic regions responsible for low-P tolerance in pearl millet is generally lacking. We present the first report on genetic polymorphisms underlying several plant P-related parameters, flowering time (FLO) and grain yield (GY) under P-limiting conditions based on 285 diversity array technology markers and 151 West African pearl millet inbred lines phenotyped in six environments in WA under both high-P and low-P conditions. Nine markers were significantly associated with P-related traits, nine markers were associated with FLO, whereas 13 markers were associated with GY each explaining between 5.5 and 15.9 % of the observed variation. Both constitutive and adaptive associations were observed for FLO and GY, with markers PgPb11603 and PgPb12954 being associated with the most stable effects on FLO and GY, respectively, across locations. There were a few shared polymorphisms between traits, especially P-efficiency-related traits and GY, implying possible colocation of genomic regions responsible for these traits. Our findings help bridge the gap between quantitative and molecular methods of studying complex traits like low-P tolerance in WA. However, validation of these markers is necessary to determine their potential applicability in marker-assisted selection programs targeting low-P environments, which are especially important in WA where resource-poor farmers are expected to be the hardest hit by the approaching global P crisis

Wpływ stresu solnego spowodowanego zasoleniem gleby na zawartość mikroelementów w liściach lip

Application of large amounts of NaCl to control slippery roads in winter leads to soil salinity and consequently to ionic imbalances, changes in pH, changes in physicochemical properties of the soil and the death of roadside trees. The aim of this study was to evaluate the effect of salt stress on the content of microelements in the leaves of roadside trees and on the health trees. The subject of research were trees of the Crimean linden (Tilia ‘Euchlora’) growing in the median strip of one of the main streets in Warsaw. The roadside trees contained much higher amounts of Cl and Na than trees in a park (control). There was a significant correlation between the Cl and Na content in leaves of the trees and their health state. As the content of these elements increased, the health condition of leaves clearly deteriorated. There was no significant effect of soil salinity on the micronutrient content in leaves. The content of Cu, Fe, Zn and Mn in linden tree leaves were on levels considered normal, with values not indicative of any deficiency or toxicity. The presence of Fe and Zn in leaves had no significant effect on the health of leaves of the trees. A statistically significant negative relationship was found between the index of leaf damage and their content of Cu and Mn. This means that a higher degree of leaf damage corresponded to a lower content of Cu and Mn. Based on regression analysis, it was estimated an increase in the Cl content in soil solution by approximately 1000 mg dm-3 caused an average 0.2% increase in the Cl content in leaves.Stosowanie dużych ilości NaCl do zwalczania śliskości dróg w okresie zimowym prowadzi do zasolenia gleb, a w konsekwencji do zaburzeń równowagi jonowej, zmian pH oraz zmian właściwości fizykochemicznych gleby i zamierania drzew przyulicznych. Celem badań była ocena wpływu stresu solnego na zawartość mikroelementów w liściach drzew ulicznych i stan zdrowotny drzew. Przedmiotem badań były drzewa lipy krymskiej (Tilia Euchlora) rosnące w pasie międzyjezdniowym głównej ulicy w Warszawie. Drzewa uliczne zawierały znacznie więcej Cl i Na niż drzewa z parku (kontrola). Stwierdzono istotne zależności między zawartością Cl i Na w liściach drzew a ich stanem zdrowotnym. Wraz ze wzrostem zawartości tych pierwiastków wyraźnie pogarszał się stan zdrowotny liści. Nie stwierdzono istotnego wpływu zasolenia gleby na zawartość mikroelementów w liściach. Zawartość Cu, Fe, Zn i Mn w liściach lip była na poziomie uznanym za „normalny”, nie stwierdzono wartości wskazujących na niedobór lub poziom toksyczny. Zawartość Fe oraz Zn w liściach nie miała istotnego wpływu na stan zdrowotny liści drzew. Stwierdzono natomiast ujemne statystycznie istotne zależności między indeksem uszkodzenia liści a zawartością w nich Cu i Mn. Oznacza to, że wraz ze wzrostem stopnia uszkodzenia liści, zmniejszała się zawartość Cu i Mn. Na podstawie analizy regresji oszacowano w przybliżeniu, że zwiększenie zawartości Cl w roztworze glebowym o 1000 mg dm-3 powoduje przeciętne zwiększenie zawartości Cl w liściach o 0,2%