90 research outputs found
Development of a Model System to Identify Differences in Spring and Winter Oat
Our long-term goal is to develop a Swedish winter oat (Avena sativa). To identify molecular differences that correlate with winter hardiness, a winter oat model comprising of both non-hardy spring lines and winter hardy lines is needed. To achieve this, we selected 294 oat breeding lines, originating from various Russian, German, and American winter oat breeding programs and tested them in the field in south- and western Sweden. By assaying for winter survival and agricultural properties during four consecutive seasons, we identified 14 breeding lines of different origins that not only survived the winter but also were agronomically better than the rest. Laboratory tests including electrolytic leakage, controlled crown freezing assay, expression analysis of the AsVrn1 gene and monitoring of flowering time suggested that the American lines had the highest freezing tolerance, although the German lines performed better in the field. Finally, six lines constituting the two most freezing tolerant lines, two intermediate lines and two spring cultivars were chosen to build a winter oat model system. Metabolic profiling of non-acclimated and cold acclimated leaf tissue samples isolated from the six selected lines revealed differential expression patterns of 245 metabolites including several sugars, amino acids, organic acids and 181 hitherto unknown metabolites. The expression patterns of 107 metabolites showed significant interactions with either a cultivar or a time-point. Further identification, characterisation and validation of these metabolites will lead to an increased understanding of the cold acclimation process in oats. Furthermore, by using the winter oat model system, differential sequencing of crown mRNA populations would lead to identification of various biomarkers to facilitate winter oat breeding
Fructan and its relationship to abiotic stress tolerance in plants
Numerous studies have been published that attempted to correlate fructan concentrations with freezing and drought tolerance. Studies investigating the effect of fructan on liposomes indicated that a direct interaction between membranes and fructan was possible. This new area of research began to move fructan and its association with stress beyond mere correlation by confirming that fructan has the capacity to stabilize membranes during drying by inserting at least part of the polysaccharide into the lipid headgroup region of the membrane. This helps prevent leakage when water is removed from the system either during freezing or drought. When plants were transformed with the ability to synthesize fructan, a concomitant increase in drought and/or freezing tolerance was confirmed. These experiments indicate that besides an indirect effect of supplying tissues with hexose sugars, fructan has a direct protective effect that can be demonstrated by both model systems and genetic transformation
Hv-CBF2A overexpression in barley accelerates COR gene transcript accumulation and acquisition of freezing tolerance during cold acclimation
Abstract C-Repeat Binding Factors (CBFs) are DNAbinding
transcriptional activators of gene pathways imparting
freezing tolerance. Poaceae contain three CBF subfamilies,
two of which, HvCBF3/CBFIII and HvCBF4/CBFIV,
are unique to this taxon. To gain mechanistic insight into
HvCBF4/CBFIV CBFs we overexpressed Hv-CBF2A in
spring barley (Hordeum vulgare) cultivar ‘Golden Promise’.
The Hv-CBF2A overexpressing lines exhibited stunted
growth, poor yield, and greater freezing tolerance compared
to non-transformed ‘Golden Promise’. Differences in
freezing tolerance were apparent only upon cold acclimation.
During cold acclimation freezing tolerance of the
Hv-CBF2A overexpressing lines increased more rapidly
than that of ‘Golden Promise’ and paralleled the freezing
tolerance of the winter hardy barley ‘Dicktoo’. Transcript
levels of candidate CBF target genes, COR14B and DHN5
were increased in the overexpressor lines at warm temperatures,
and at cold temperatures they accumulated to much
higher levels in the Hv-CBF2A overexpressors than in
‘Golden Promise’. Hv-CBF2A overexpression also
increased transcript levels of other CBF genes at FROST
RESISTANCE-H2-H2 (FR-H2) possessing CRT/DRE sites
in their upstream regions, the most notable of which was
CBF12. CBF12 transcript levels exhibited a relatively constant
incremental increase above levels in ‘Golden Promise’
both at warm and cold. These data indicate that Hv-CBF2A
activates target genes at warm temperatures and that transcript
accumulation for some of these targets is greatly
enhanced by cold temperatures
Transcriptional responses of winter barley to cold indicate nucleosome remodelling as a specific feature of crown tissues
We report a series of microarray-based comparisons of gene expression in the leaf and crown of the winter barley cultivar Luxor, following the exposure of young plants to various periods of low (above and below zero) temperatures. A transcriptomic analysis identified genes which were either expressed in both the leaf and crown, or specifically in one or the other. Among the former were genes responsible for calcium and abscisic acid signalling, polyamine synthesis, late embryogenesis abundant proteins and dehydrins. In the crown, the key organ for cereal overwintering, cold treatment induced transient changes in the transcription of nucleosome assembly genes, and especially H2A and HTA11, which have been implicated in cold sensing in Arabidopsis thaliana. In the leaf, various heat-shock proteins were induced. Differences in expression pattern between the crown and leaf were frequent for genes involved in certain pathways responsible for osmolyte production (sucrose and starch, raffinose, γ-aminobutyric acid metabolism), sugar signalling (trehalose metabolism) and secondary metabolism (lignin synthesis). The action of proteins with antifreeze activity, which were markedly induced during hardening, was demonstrated by a depression in the ice nucleation temperature
On Leading Meetings: Linking Meeting Outcomes to Leadership Styles
Leading meetings represent a typically and frequently performed leadership task. This study investigated the relationship between the leadership style of supervisors and employees’ perception of meeting outcomes. Results showed that participants reported greater meeting satisfaction when their meeting leader was assessed as a considerate supervisor, with the relationship between considerate leadership style and meeting satisfaction being mediated by both relational- and task-oriented meeting procedures. The results, however, provide no support for initiating structure being associated with meeting effectiveness measures. More generally, the findings imply that leadership behavior is a crucial factor in explaining important meeting outcomes
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