A specific group of genes respond to cold dehydration stress in cut Alstroemeria flowers whereas ambient dehydration stress accelerates developmental senescence expression patterns

Petal development and senescence entails a normally irreversible process. It starts with petal expansion and pigment production, and ends with nutrient remobilization and ultimately cell death. In many species this is accompanied by petal abscission. Post-harvest stress is an important factor in limiting petal longevity in cut flowers and accelerates some of the processes of senescence such as petal wilting and abscission. However, some of the effects of moderate stress in young flowers are reversible with appropriate treatments. Transcriptomic studies have shown that distinct gene sets are expressed during petal development and senescence. Despite this, the overlap in gene expression between developmental and stress-induced senescence in petals has not been fully investigated in any species. Here a custom-made cDNA microarray from Alstroemeria petals was used to investigate the overlap in gene expression between developmental changes (bud to first sign of senescence) and typical post-harvest stress treatments. Young flowers were stressed by cold or ambient temperatures without water followed by a recovery and rehydration period. Stressed flowers were still at the bud stage after stress treatments. Microarray analysis showed that ambient dehydration stress accelerates many of the changes in gene expression patterns that would normally occur during developmental senescence. However, a higher proportion of gene expression changes in response to cold stress were specific to this stimulus and not senescence related. The expression of 21 transcription factors was characterized, showing that overlapping sets of regulatory genes are activated during developmental senescence and by different stresses

Genomic analysis of NAC transcription factors in banana (Musa acuminata) and definition of NAC orthologous groups for monocots and dicots

Identifying the molecular mechanisms underlying tolerance to abiotic stresses is important in crop breeding. A comprehensive understanding of the gene families associated with drought tolerance is therefore highly relevant. NAC transcription factors form a large plant-specific gene family involved in the regulation of tissue development and responses to biotic and abiotic stresses. The main goal of this study was to set up a framework of orthologous groups determined by an expert sequence comparison of NAC genes from both monocots and dicots. In order to clarify the orthologous relationships among NAC genes of different species, we performed an in-depth comparative study of four divergent taxa, in dicots and monocots, whose genomes have already been completely sequenced: Arabidopsis thaliana, Vitis vinifera, Musa acuminata and Oryza sativa. Due to independent evolution, NAC copy number is highly variable in these plant genomes. Based on an expert NAC sequence comparison, we propose forty orthologous groups of NAC sequences that were probably derived from an ancestor gene present in the most recent common ancestor of dicots and monocots. These orthologous groups provide a curated resource for large-scale protein sequence annotation of NAC transcription factors. The established orthology relationships also provide a useful reference for NAC function studies in newly sequenced genomes such as M. acuminata and other plant species

Identification of quantitative trait loci (QTL) for drought tolerance and leaf senescence in juvenile barley

Im Rahmen des Klimawandels kommt der Toleranz gegenüber Trockenstress eine steigende Bedeutung zu. Durch die durch Trockenstress ausgelöste frühzeitige Blattseneszenz kommt es zu einem Abbruch der Photosynthese und frühzeitig zu Umlagerungsprozessen von gespeicherten Assimilaten in das Korn. Da eine Phänotypisierung auf Trockenstress und Seneszenz in den Züchtungsprozess der Gerste nur schwer zu integrieren ist, sind arkergestützte Selektionsverfahren von Vorteil. Ziel dieser Arbeit war es daher, mittels genomweiter Assoziationsstudien (GWAS) Marker zu identifizieren, die mit Trockenstress-, oder Blattseneszenzparametern in juveniler Gerste assoziiert sind. Für die Phänotypisierung hinsichtlich der Reaktion auf Trockenstress und dadurch induzierter Blattseneszenz, wurde ein Screening- Verfahren entwickelt, welches eine verlässliche Erfassung dieser Merkmale erlaubt. 156 Wintergerstengenotypen wurden in frühen Entwicklungsstadien im Gewächshaus unter Kontroll- und Stressbedingungen analysiert. Die Trockenstressapplikation erfolgte vom Primärblattstadium für 4 Wochen. In diesen Versuchen wurden sechs physiologische Merkmale erfasst (Biomasse, Blattfarbe, Elektronentransportrate am Photosystem II, Osmolalität, Gehalt an freien Prolin und der Gesamtgehalt an löslichen Zuckern), sowie Expressionsstudien für Gene welche in die Trockenstressreaktion bzw. die Seneszenz involviert sind, durchgeführt. Für diese Merkmale und die Expression der 14 ausgewählten Gene konnten signifikante Genotypund Behandlungseffekte nachgewiesen werden. Anhand dieser Daten und 3.212 SNP Markern des Illumina 9k iSelect Chips wurden GWAS durchgeführt, um Genomregionen (QTL und eQTL) zu lokalisieren. Insgesamt konnten für die physiologischen Merkmale 47 QTL für die Reaktion auf Trockenstress, und weiterhin 15 eQTL identifiziert werden. Dabei wurden zwei Haupt- QTL-Regionen auf Chromosom 2H bei 50 cM und 5H bei 45 cM lokalisiert, in denen einige QTL für unterschiedliche Parameter, wie Biomasse und Blattfarbe nachgewiesen wurden. In diesen QTL-Regionen wurden Proteine identifiziert, die im Zusammenhang mit Trockenstress und Blattseneszenz stehen. Vier der regulierenden Gene zeigten eine differentielle Expression und es wurden entsprechend eQTL identifiziert. Ein eQTL für TRIUR3 stimmte mit dem, mittels phänotypischer Daten identifizierten QTL auf Chromosom 5H überein. Die assoziierten Marker BOPA1_9766-787 und SCRI_RS_102075 können nach Validierung geeignete Marker für eine Selektion auf Trockenstresstoleranz und Blattseneszenz in der Gerstenzüchtung darstellen.Drought stress as a trait with increasing importance in the background of climate change is an important factor limiting barley yield. Induced by drought, leaf senescence may occur prematurely, leading to a stop of photosynthesis and to an early translocation of stored assimilates into grains. For barley breeding, the identification of quantitative trait loci (QTL) involved in drought stress and leaf senescence may be an advantage as reliable phenotyping for drought stress is difficult to achieve. Therefore, the aim of the present thesis was to identify markers associated to drought stress response and drought stress induced leaf senescence in juvenile barley through genome wide association studies (GWAS), which will facilitate efficient marker based selection procedures. In a first step, a screening method was developed for analysing drought stress response and early leaf senescence in juvenile barley. Next, in semi controlled greenhouse pot experiments 156 winter barley genotypes were analysed in early developmental stages under control and drought stress treatment. Drought application started at the primary leaf stage and continued for a four weeks stress period. These experiments were used for phenotyping six physiological parameters (biomass yield, leaf colour, electron transport rate at photosystem II, osmolality, content of free proline and total content of soluble sugars), as well as for gene expression analysis of genes involved in drought stress and leaf senescence. Significant genotypic and treatment effects were detected for all phenotypic traits and gene expression data. Based on these data and on 3,212 SNP markers of the Illumina 9k iSelect Chip, GWAS were conducted to detect QTL and expression QTL (eQTL). In total, 47 significant QTL were identified for the traits analysed under drought stress conditions and 15 significant eQTL were found for the relative expression of the 14 genes involved in these traits. Under drought stress conditions, two major QTL regions overlapping for different traits such as biomass yield and leaf colour were detected on chromosome 2H at 50 cM and on chromosome 5H at 45 cM. In these QTL, genes coding for proteins involved in drought stress or leaf senescence were identified. Four of these genes showed a differential expression and thus, eQTL were detected. One eQTL for TRIUR3 coincides with the phenotypic QTL on chromosome 5H. After validation respective markers BOPA1_9766-787 and SCRI_RS_102075 may be used in future barley breeding programmes for improving tolerance to drought stress and leaf senescence

Translational regulation contributes to the elevated CO2 response in two Solanum species.

Understanding the impact of elevated CO2 (eCO2 ) in global agriculture is important given climate change projections. Breeding climate-resilient crops depends on genetic variation within naturally varying populations. The effect of genetic variation in response to eCO2 is poorly understood, especially in crop species. We describe the different ways in which Solanum lycopersicum and its wild relative S. pennellii respond to eCO2 , from cell anatomy, to the transcriptome, and metabolome. We further validate the importance of translational regulation as a potential mechanism for plants to adaptively respond to rising levels of atmospheric CO2

Osmoregulators proline and glycine betaine counteract salinity stress in canola

Salt inundation leads to increased salinization of arable land in many arid and semi-arid regions. Until genetic solutions are found farmers and growers must either abandon salt-affected fields or use agronomic treatments that alleviate salt stress symptoms. Here, field experiments were carried out to study the effect of the osmoregulators proline at 200 mg L-1 and glycine betaine at 400 mg L-1 in counteracting the harmful effect of soil salinity stress on canola plants grown in Egypt. We assessed growth characteristics, yield and biochemical constituents. Results show first that all growth characters decreased with increasing salinity stress but applied osmoregulators alleviated these negative effects. Second, salinity stress decreased photosynthetic pigments, K and P contents, whilst increasing proline, soluble sugars, ascorbic acid, Na and Cl contents. Third, application of osmoregulators without salt stress increased photosynthetic pigments, proline, soluble sugars, N, K and P contents whilst decreasing Na and Cl contents. It is concluded that the exogenously applied osmoregulators glycine betaine and proline can fully or partially counteract the harmful effect of salinity stress on growth and yield of canola.© INRA and Springer-Verlag, France 2012

Tomato (Solanum lycopersicum L.) in the service of biotechnology

Originating in the Andes, the tomato (Solanum lycopersicum L.) was imported to Europe in the 16th century. At present, it is an important crop plant cultivated all over the world, and its production and consumption continue to increase. This popular vegetable is known as a major source of important nutrients including lycopene, bcarotene, flavonoids and vitamin C as well as hydroxycinnamic acid derivatives. Since the discovery that lycopene has anti-oxidative, anti-cancer properties, interest in tomatoes has grown rapidly. The development of genetic engineering tools and plant biotechnology has opened great opportunities for engineering tomato plants. This review presents examples of successful tissue culture and genetically modified tomatoes which resistance to a range of environmental stresses improved, along with fruit quality. Additionally, a successful molecular farming model was established