199 research outputs found
Efficient cell reprogramming as a target for functional-marker strategies? Towards new perspectives in applied plant-nutrition research
The review aims at visualizing and strengthening approximation of current strategies in plant breeding, plant nutrition, and molecular biology. Innovations in new breeding strategies on quantitative traits are based on the development of functional DNA markers. This requires knowledge on robust physiological key reactions or parameters in view of the desired agronomic trait. To understand the significance of adaptive molecular-physiological factors for the expression of agronomic traits in quantitative terms, systems analyses have to demonstrate the phenotypic effect of differential gene activities. The logistic to advance in applied systems biology is currently being strongly discussed. In the present contribution, identification of target cells, which are important for agronomic traits, is stressed as a key for future modeling and virtual experimentation. Integration of target cells in systems analysis should allow to link top-down approaches, that start at the whole-plant level, with bottom-up approaches, that come from the molecular level. To illustrate the importance of adaptive cell reprogramming for agronomic traits, reprogramming of rhizodermic cells to trichoblasts is pointed out in its role for nutrient efficiency (NE). The nature of molecular factors, which may serve as functional markers in breeding, is discussed in view of future marker development
Unravelling wild carrot differentiation in Europe: preliminary data on a candidate gene approach
Carrot is an outcrossing species and levels of gene flow between populations,
and even between wild and domesticated relatives, are expected to be high. Cases of
natural hybridization and introgression of crops and wild relatives have been
reported. Have these events diluted any putative habitat-adapted genotypes? In other
words, can we still find a correlation between wild carrot genotypes and
regional/local environment? We have chosen to start addressing this question using a
member of the alternative oxidase (AOX) gene family. AOX genes seem to be linked to
all kinds of abiotic and biotic stress reactions. Wild carrots were sampled in an
environmental gradient across Western Europe. This gradient included sampling
points with more deviating conditions, such as Sierra de Guadarrama or the central
Pyrenees and the French Massif Central. Phylogenetic reconstruction on this
molecular marker is to be combined with geographic, climatic, and ecological
evidence. So far, the preliminary results suggest the existence of a biogeographical
barrier at the Pyrenees, and higher gene diversity than initially expected. From an
applied point of view, diversity of functional traits is much more relevant than species
diversity. Gene transfer from wild to cultivated plants has contributed to the evolution
of crop species. Providing that deterioration of genetic resources and biodiversity loss
have not been drastic, gene transfer from wild plants has the potential to further
contribute to a (targeted) improvement of cultivars.info:eu-repo/semantics/publishedVersio
Reference Genes Selection and Normalization of Oxidative Stress Responsive Genes upon Different Temperature Stress Conditions in Hypericum perforatum L
Abstract
Reverse transcription-quantitative real-time PCR (RT-qPCR) is a widely used
technique for gene expression analysis. The reliability of this method depends
largely on the suitable selection of stable reference genes for accurate data
normalization. Hypericum perforatum L. (St. John’s wort) is a field growing plant that
is frequently exposed to a variety of adverse environmental stresses that can
negatively affect its productivity. This widely known medicinal plant with broad
pharmacological properties (anti-depressant, anti-tumor, anti-inflammatory,
antiviral, antioxidant, anti-cancer, and antibacterial) has been overlooked with
respect to the identification of reference genes suitable for RT-qPCR data
normalization. In this study, 11 candidate reference genes were analyzed in H.
perforatum plants subjected to cold and heat stresses. The expression stability of
these genes was assessed using GeNorm, NormFinder and BestKeeper
algorithms. The results revealed that the ranking of stability among the three
algorithms showed only minor differences within each treatment. The best-ranked
reference genes differed between cold- and heat-treated samples; nevertheless,
TUB was the most stable gene in both experimental conditions. GSA and GAPDH
were found to be reliable reference genes in cold-treated samples, while GAPDH
showed low expression stability in heat-treated samples. 26SrRNA and H2A had
the highest stabilities in the heat assay, whereas H2A was less stable in the cold
assay. Finally, AOX1, AOX2, CAT1 and CHS genes, associated with plant stress
responses and oxidative stress, were used as target genes to validate the reliability
of identified reference genes
Aox gene structure, transcript variation and expression in plants
Alternative oxidase (Aox) has been proposed as a functional marker for breeding stress tolerant plant varieties. This requires presence of polymorphic Aox allele sequences in plants that affect plant phenotype in a recognizable way. In this review, we examine the hypothesis that organization of genomic Aox sequences and gene expression patterns are highly variable in relation to the possibility that such a variation may allow development of Aox functional markers in plants. Aox is encoded by a small multigene family, typically with four to five members in higher plants. The predominant structure
of genomic Aox sequences is that of four exons interrupted by three introns at well conserved positions. Evolutionary intron loss and gain has resulted in the variation of intron numbers in some Aox members that may harbor two to four introns and three to five exons in their sequence. Accumulating
evidence suggests that Aox gene structure is polymorphic enough to allow development of Aox markers in many plant species. However, the functional significance of Aox structural variation has not been examined exhaustively. Aox expression patterns display variability and typically Aox genes fall into two discrete subfamilies, Aox1 and Aox2, the former being present in all plants and the latter restricted in eudicot species. Typically, although not exclusively, the Aox1-type genes are induced by many different kinds of stress, whereas Aox2-type genes are expressed in a constitutive or developmentally regulated way. Specific Aox alleles are among the first and most intensively stressinduced
genes in several experimental systems involving oxidative stress. Differential response of Aox genes to stress may provide a flexible plan of plant defense where an energy-dissipating system in mitochondria is involved. Evidence to link structural variation and differential allele expression patterns is scarce. Much research is still required to understand the significance of polymorphisms within AOX gene sequences for gene regulation and its potential for breeding on important agronomic traits.
Association studies and mapping approaches will be helpful to advance future perspectives for application more efficiently
Temperature responses of substrate carbon conversion efficiencies and growth rates of plant tissues
Growth rates of plant tissues depend on both the respiration rate and the efficiency with which carbon is incorporated into new structural biomass. Calorespirometric measurement of respiratory heat and
CO2 rates, from which both efficiency and growth rate can be calculated, is a well established method for determining the effects of rapid temperature changes on the respiratory and growth properties of plant tissues. The effect of the alternative oxidase/cytochrome oxidase activity ratio on efficiency is calculated from first principles. Data on the temperature dependence of the substrate carbon
conversion efficiency are tabulated. These data show that ε is maximum and approximately constant through the optimum growth temperature range and decreases rapidly as temperatures approach temperature limits to growth. The width of the maximum and the slopes of decreasing ε at high and
low temperatures vary greatly with species, cultivars and accessions
Isolation of alternative oxidase (AOX) genes of Olea europaea L.
Alternative oxidase (AOX) is recently suggested to be a potential candidate as functional marker for efficient cell reprogramming under stress (Arnholdt-Schmitt et al., 2006a). The presented work is part
of a Marie Curie Chair project, that was established to investigate the potential role of the multigene AOX to assist breeding on efficient rooting of olive shoot cuttings (Arnholdt-Schmitt et al. 2006b). Plant
mito-chondrial AOX is a small nuclear-encoded multigene family consisting of the two subfamilies AOX1 and AOX2. The intron-exon structure of AOX has been well characterized in several species,
revealing a large degree of conservation. Here we report for the first time about the isolation of AOX multigene se-quences of olive (Olea europaea L.). The genes were isolated from a portuguese clone of the landrace ‘Galega vulgar’
AOX a functional marker for efficient cell reprogramming under stress?
Functional markers for stress tolerance can be used in plant breeding to identify genotypes with high yield stabilities under various conditions. Thus, a good marker should show a strong correlation with
favourable adaptive plant behaviour. The efficient reprogramming of target cells for yield determination is currently considered to be the most important step towards defining abiotic stress tolerance. In this
Opinion article, we propose a role for the alternative oxidase (AOX) gene as a marker for genetic variation in cell reprogramming and yield stability. Evidence to support this idea comes from the metabolic role of alternative respiration under stress, the link between AOX activity and differential
growth, and the single nucleotide polymorphism recently observed in AOX genes. We propose an innovative, interdisciplinary and global research strategy for future experimentation on AOX genes that could have an application in plant breeding
Intron polymorphism pattern in AOX1b of wild St John's wort (Hypericum perforatum) allows discrimination between individual plants
The present paper deals with the analysis of natural polymorphism in a selected alternative oxidase (AOX) gene of the medicinal plant, St John's wort. Four partial AOX gene sequences were isolated from the genomic DNA of a wild plant of Hypericum perforatum L. Three genes belong to the subfamily AOX1 (HpAOX1a, b and c) and one to the subfamily AOX2 (HpAOX2). The partial sequence of HpAOX1b showed polymerase chain reaction (PCR)
fragment size variation as a result of variable lengths in two introns. PCR performed by Exon Primed Intron
Crossing (EPIC)-PCR displayed the same two-band pattern in six plants from a collection. Both fragments showed identical sequences for all exons. However, each of the two introns showed an insertion/deletion (InDel) in identical positions for all plants that counted for the difference in the two fragment sizes. The InDel in intron 1
influenced the predictability of a pre-microRNA site. The almost identical PCR fragment pattern was characterized by a high variability in the sequences. The InDels in both introns were linked to repetitive intron single nucleotide polymorphisms (ISNP)s. The polymorphic pattern obtained by InDels and ISNPs from both fragments together
was appropriate to discriminate between all individual plants. We suggest that AOX sequence polymorphism in H.
perforatum can be used for studies on gene diversity and biodiversity. Further, we conclude that AOX sequence polymorphism of individual plants should be considered in biological studies on AOX activity to exclude the influence of genetic diversity. The identified polymorphic fragments are available to be explored in future experiments as a potential source for functional marker development related to the characterization of origins/accessions and agronomic traits such as plant growth, development and yield stability
Alternative oxidase involvement in Daucus carota somatic embryogenesis
Plant alternative oxidase (AOX) is a mitochondrial inner membrane enzyme involved in alternative respiration.The critical importance of the enzyme during acclimation upon stress of plant cells is not fully understood and is still an issue of intensive research and discussion. Recently, a role of AOX was suggested for the ability of plant cells to change easily its fate upon stress. In order to get new insights about AOX involvement in cell reprogramming, quantitative real-time polymerase chain reaction (PCR) and inhibitor studies were performed during cell redifferentiation and developmental stages of Daucus carota L. somatic embryogenesis. Transcript
level analysis shows that D. carota AOX genes (DcAOX1a and DcAOX2a) are differentially expressed during somatic embryogenesis. DcAOX1a shows lower expression levels, being mainly down- regulated, whereas DcAOX2a presented a large up-regulation during initiation of the realization phase of somatic embryogenesis.
However, when globular embryos start to develop, both genes are down-regulated, being this state transient for DcAOX2a. In addition, parallel studies were performed using salicylhydroxamic acid (SHAM) in order to inhibit AOX activity during the realization phase of somatic embryogenesis. Embryogenic cells growing in the presence
of the inhibitor were unable to develop embryogenic structures and its growth rate was diminished. This effect was reversible and concentration dependent. The results obtained contribute to the hypothesis that AOX activity supports metabolic reorganization as an essential part of cell reprogramming and, thus, enables restructuring and de novo cell differentiation
Induction of somatic embryogenesis as an example of stress-related plant reactions
In this review, we address the role of stress as one of the principal causes for a cell
or tissue to change its preexisting somatic program, reprogramming itself to express
the embryogenic pathway. The focus of this paper is the effect of different stress
conditions on the induction phase of plant somatic embryogenesis, as well as the
development of embryogenic competence as a result of the applied stresses. We
also present a variety of data that link plant somatic embryogenesis, DNA
methylation and oxidative stress response
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