Plant growth and productivity is largely hampered by a number of abiotic stresses. These stresses affect the physiological and metabolic pathways leading to the production of many harmful substances like aldehydes, reactive ...

The present study focused on the cellular and molecular gravisensing-related processes in Arabidopsis and in the unicellular rhizoids of the green alga Chara. Experiments during sounding-rocket and parabolic plane flights ...

Understanding species distribution patterns and the corresponding environmental determinants is a crucial step in the development of effective strategies for the conservation and management of plant communities and ecosystems. ...

Many plants and animals feature superhydrophobic surfaces capable of retaining a layer of air when submerged under water. The most persistent air layers can last for weeks and even month and are maintained by hairy surfaces ...

Improving crop yield under water deficit environments is an urgent task for crop breeding worldwide. Many efforts have been made to identify key regulators of plant drought stress responses. Most of these studies have been performed with the model plant Arabidopsis thaliana under controlled laboratory conditions. Little work has been done to investigate the functions of these key regulators in the improvement of drought tolerance in crops, especially under field conditions. In the present study, ten barley CBF/DREB gene transcripts (CBF1, CBF2, CBF3, CBF4, CBF6, CBF11, DREB1, DRF1.1, DRF1.3 and DRF2) were isolated from different barley cultivars by using gene-specific primers. Phylogenetic analysis showed that all candidate CBF/DREB genes can be grouped into three phylogenetic subgroups, designated HvCBF1, HvCBF4 and HvDREB1. The phylogenetic distribution of barley CBF/DREB genes in the reconciled tree coincides with their responses to drought. A strongly constitutive expression of the HvDREB1, HvDRF1.1 and HvDRF1.3 genes upon drought has been identified in this study, which is contrary to the published data in the literature. This may be due to the age and physiological state of the plants. By analyzing the CBF expression patterns upon drought in leaf tissues of plants grown in the field, we found that barley cultivars respond to drought at different time points. Monitoring the expression of HvCBF1, HvCBF2, HvCBF3, HvCBF4, HvCBF6 and HvCBF11 transcripts upon drought in field grown material revealed that rapid dehydration triggered the reduction of the above-mentioned transcripts. This was further validated by experiments performed under controlled laboratory conditions. Furthermore, tissue- and age-dependent expression has been identified in barley HvCBF1, HvCBF3, HvCBF4, HvCBF6 and HvCBF11 genes, indicating that the CBF transcription factors are developmentally regulated. Importantly, in contrast to the common thought, our analyses of methylation patterns in the HvCBF1 promoter showed that DNA methylation within the promoter does not always lead to down-regulation of the corresponding gene. Finally, a more efficient and non-invasive method to analyze the barley root architecture and development has been initiated with help and permissions from Prof. Dr. Philip Benfey, Duke University, Durham NC, USA....

Paleo-vegetation of northern Israel is reconstructed from palynological data over the Late Pleistocene and Holocene, and related to climate variation in the Levant, as well as anthropogenic impact on vegetation. Being ...

Ziel meiner Arbeit war es, anhand ausgewählter Lipidstoffwechsel-Mutanten Rückschlüsse auf die Beteiligung der untersuchten Gene an der Polyesterbildung von Kutin und Suberin zu ziehen. Untersucht wurden die Polyesterzusammensetzungen einer CYP450-abhängigen ω-Hydroxylase Bncyp704b1 in Brassica napus, einer BAHD-Acyltransferase Sldcr in Solanum lycopersicum, einem ABC-Transporter abcg11, sowie die Transkriptionsfaktorenfamilie shn1, shn2 und shn3 in Arabidopsis thaliana. <br /> In B. napus wurde die doppelt rezessive Linie des Gens BnCYP704B1 untersucht. Die Mutante Bncyp704b1 weist im Vergleich zum Wildtyp vergrößerte Antheren mit veränderter Kutikulazusammensetzung und defekte Pollenwände, mit Folge einer Semisterilität, auf. In der Mutante wurde ein Defizit von C16- und C18-ω-Hydroxysäuren und deren Folgeprodukte im Antherenkutin nachgewiesen. In Anlehnung an den Polyesterbiosyntheseweg und anhand der Resultate konnte die putative ω-Hydroxylasefunktion für C₁₆- und C₁₈-Fettsäuren in der Kutinbildung der Antherenkutikula bestätigt werden. <br /> Der RNAi-Knockdown des SlDCR-Gens führte in S. lycopersicum zu enormen Veränderungen der Morphologie der Tomatenfruchtschale. Mikroskopische Untersuchungen der braungefärbten Schale zeigten, dass die Tomatenfruchtschale mehrere Zelllagen aufweist, die unter UV-Licht fluoreszieren. Durch Transportstudien mit isolierten Kutikeln konnte eine erhöhte Wasserpermeabilität nachgewiesen werden. Die Analyse der chemischen Zusammensetzung der Kutikula ergab, sowohl bei den Wachsen als auch im Kutin, drastische Veränderungen der Kompositionen, was die Beteiligung des Gens an der Kutikulabildung belegt. Die Reduktion der C16-9/10-Dihydroxyfettsäuremenge (C₁₆-DHFS) und die Akkumulation der Vorstufen im Kutin belegen die SlDCR-Beteiligung an der C16-DHFS-Synthese. Die Sequenzhomologie zum Ortholog AtDCR und in vitro Studien der AtDCR führen zur Annahme, dass es sich bei der SlDCR ebenfalls um eine BAHD-Acyltransferase handelt die CoA-aktivierte C16 ω Hydroxysäuren mit Glycerin verknüpft, woraus folgend C₁₆-DHFS-glycerin gebildet wird. <br /> Der ABC-Transporter ABCG11 wurde mithilfe von Cosuppressionslinien des Gens untersucht bei denen die Polyesterzusammensetzungen von Sprossachse, Blatt, Wurzel, Blüte und Schote analysiert wurden. Es konnten in allen Polyestern veränderte Zusammensetzungen beobachtet werden, welche im Kutin die Substanzklassen der ω-Hydroxysäuren, Disäuren und mittkettig oxygenierten Säuren betrafen und im Suberin die der ω-Hydroxysäuren und Disäuren. Da in allen Polyestern der Knockdownlinien nur die Disäuren eine Verringerung und in Überexpressionslinien eine Erhöhung zeigten, was schlüssig mit der ABCG11-Transportermenge ist, konnte die Substratspezifität für den ABCG11-Transporter auf gesättigte und ungesättigte C₁₆-/C₁₈-Disäuren eingeengt werden. <br /> Die SHINE-Transkriptionsfaktorenfamilie wurde mithilfe eines artifiziellen RNAi Knockdowns mit den drei Mitgliedern dieser Familie als Target in A. thaliana untersucht. Die shine-Linien wiesen Organfusionen in der Blüte auf. Die Analyse der Kutikulazusammensetzung ergab in der Mutante eine Verringerung des Blütenkutins und eine Erhöhung der Alkane der Blattwachse. Im Kutin konnte das Defizit an den C₁₆-und C₁₈-ω-Hydroxysäuren, Disäuren und mittkettig oxygenierten Säuren ausgemacht werden. Auf Grundlage des bisher bekannten Kutinsynthesewegs und durch Expressionsstudien konnten die ω-Hydroxylasegene CYP86A4 und CYP86A7 und die Mittketten-Alkan-Hydroxylase CYP96A15 als SHINE-Target ausgemacht werden....

Alle primären oberirdischen Pflanzenorgane werden von der Kutikula bedeckt, die die Grenzfläche zwischen Pflanze und Umwelt bildet. Die Kutikula ist eine extrazelluläre lipophile Membran, bestehend aus dem Polymer Kutin ...

The resurrection plant Craterostigma plantagineum, a member of Linderniaceae family, is distributed in areas with variable water availability in Southern Africa. Two closely related species, L. brevidens which is endemic to montan rain forest of Africa and L. subracemosa which is found in central and Southern Africa, are used for comparative analyses for unravelling the molecular mechanisms of desiccation tolerance. While C. plantagineum and L. brevidens are desiccation tolerant, L. subracemosa represents a desiccation sensitive species. Desiccation tolerance is a very complex trait. Many genes that are involved in desiccation tolerance and the proteins that are encoded by these genes have been characterized in C. plantagineum. The Cp LEA-like 11-24 is one of these stress inducible genes in C. plantagineum that has been extensively studied both at the transcriptional and posttranscriptional level. Studies have been performed on the promoter regulation and transcription factor binding along with comparative promoter analyses between two desiccation tolerant and a desiccation sensitive species. Since promoter regions are the main regulatory elements for enhancing the transcriptional efficiency, developing an efficient transient transformation system was required to analyze promoter functions in response to different abiotic stresses. In this study, an efficient Agrobacterium-mediated transient transformation method was developed in three closely related Linderniaceae species. Different parameters that are important for enhancing the transformation efficiency were considered. These parameters include leaf size, Silwet L-77 concentration, bacterial density and duration of co-cultivation. After optimization, the activities of the minimal stress inducible promoter fragments of the LEA-like 11-24 from three species were examined under ABA and osmotic stress using optimized Agrobacterium co-cultivation method. <br /> The transformation efficiency was found to be 100% in all three species. In addition, the induction pattern of each promoter fragment under ABA and osmotic stress was comparable with that of stably transformed plants or particle bombardment, suggesting this as the most suitable method for quantitatively analyzing promoter activity in the three species. The optimized method was used for cross comparison of the LEA-like 11-24 promoter fragments among two desiccation tolerant and a sensitive species to understand the effect of trans-regulatory factors in activating the LEA-like 11-24 promoter fragments. The results demonstrated that both desiccation tolerant and sensitive species contain essential trans-regulatory factors for the activity of LEA-like 11-24 promoter fragments. Using a yeast-one-hybrid system, it was previously shown the Cp LEA-like 11-24 promoter fragment interacts with CpbZIP1 protein. The CpbZIP1 belongs to the S1-class of AtbZIP transcription factors from Arabidopsis and has been shown to have 47% protein sequence identity with AtbZIP53. Transcript expression analysis of CpbZIP1 in response to ABA, dehydration and salt stress demonstrated the stress responsiveness of this gene. S1-class members of AtbZIP from Arabidopsis have complex expression patterns in different stress responses. The CpbZIP1 from C. plantagineum also showed similar complex expression pattern in response to stress. The function of CpbZIP1 transcription is completely unknown in C. plantagineum. In a functional study of the CpbZIP1 transcription factor, transgenic Arabidopsis plants overexpressing CpbZIP1 exhibited dwarf phenotype, abnormality in flower structure and small siliques suggesting that CpbZIP1 interferes with the developmental processes. Physiological and molecular data from transgenic plants overexpressing CpbZIP1 revealed the contribution of CpbZIP1 in remobilization of carbon/nitrogen or maintaining homeostasis of energy, as obtained for the bZIP homologue in Arabidopsis (AtbZIP53). Time dependent expression of CpbZIP1 revealed that apart from the function of CpbZIP1 in abiotic stress, most likely CpbZIP1 is regulated by circadian clock rhythm. The results from this study suggests that CpbZIP1 is stress inducible and involved in multiple functions like growth, flower development, accumulation of proline, remobilizing carbon/nitrogen and maintaining homeostasis of energy in low energy conditions....

The soil bacterium and plant pathogen <i>Agrobacterium tumefaciens</i> has the ability to transfer a defined part of its genome, the so called transferred DNA (T-DNA), to plant cells. This transfer has been successfully ...