Aldehyde Dehydrogenases in Arabidopsis thaliana: Biochemical Requirements, Metabolic Pathways, and Functional Analysis

Aldehyde dehydrogenases (ALDHs) are a family of enzymes which catalyze the oxidation of reactive aldehydes to their corresponding carboxylic acids. Here we summarize molecular genetic and biochemical analyses of selected Arabidopsis ALDH genes. Aldehyde molecules are very reactive and are involved in many metabolic processes but when they accumulate in excess they become toxic. Thus activity of aldehyde dehydrogenases is important in regulating the homeostasis of aldehydes. Overexpression of some ALDH genes demonstrated an improved abiotic stress tolerance. Despite the fact that several reports are available describing a role for specific ALDHs, their precise physiological roles are often still unclear. Therefore a number of genetic and biochemical tools have been generated to address the function with an emphasis on stress-related ALDHs. ALDHs exert their functions in different cellular compartments and often in a developmental and tissue specific manner. To investigate substrate specificity, catalytic efficiencies have been determined using a range of substrates varying in carbon chain length and degree of carbon oxidation. Mutational approaches identified amino acid residues critical for coenzyme usage and enzyme activities

Superhydrophobic Terrestrial Cyanobacteria and Land Plant Transition

Plants and other organisms have evolved structures and mechanisms for colonizing land since the Early Ordovician. In this context, their surfaces, the crucial physical interface with the environment, are mainly considered barriers against water loss. It is suggested that extreme water repellency (superhydrophobicity) was an additional key innovation for the transition of algae from water to land some 400 mya. Superhydrophobicity enhances gas exchange on land and excludes aquatic competitors in water films. In a different context, in material science and surface technology, superhydrophobicity has also become one of the most important bioinspired innovations enabling the avoidance of water films and contamination. Here, we present data for an extremely water-repellent cyanobacterial biofilm of the desiccation tolerant Hassallia byssoidea providing evidence for a much earlier prokaryotic Precambrian (ca. 1–2 bya) origin of superhydrophobicity and chemical heterogeneities associated with land transition. The multicellular cyanobacterium is functionally differentiated in a submerged basal hydrophilic absorbing portion like a “rhizoid” and an upright emersed superhydrophobic “phyllocauloid” filament for assimilation, nitrogen fixation, and splash dispersed diaspores. Additional data are provided for superhydrophobic surfaces in terrestrial green algae and in virtually all ancestral land plants (Bryophytes, ferns and allies, Amborella, Nelumbo), slime molds, and fungi. Rethinking of superhydrophobicity as an essential first step for life in terrestrial environments is suggested

Methodik

Die vegetationskundliche und strukturelle Zuordnung der Lebensraumtypen erfolgt nach der vorrangig von Braun-Blanquet entwickelten Vegetationsklassifizierung, einer hierarchischen Gliederung der Vegetationstypen (Syntaxonomie), die die Ebenen der Assoziation, des Verbandes, der Ordnung und der Klasse umfasst. Hierbei ist die Assoziation die grundlegende Einheit, in der die Pflanzengesellschaften zusammengefasst werden, die sich durch gleiche charakteristische Arten(gruppen)kombinationen auszeichnen. Der Verband vereinigt ähnliche Assoziationen. Das sind bereits umfassendere, jedoch standörtlich noch recht einheitliche Vegetationseinheiten. In Ordnungen werden ähnliche Verbände zusammengefasst. Die Klasse vereinigt ähnliche Ordnungen

Promoting orphan crops research and development

Orphan crops are crops with little significance at the global scale but they play a vital role in the food and nutrition security as well as the livelihood of resource-poor farmers and consumers in the developing world. The term ‘orphan’ refers to the neglect of the crop by the international research community. Orphan crops are also known as indigenous-, lost-, minor-, promising-, and underutilized-crops, among other names (Tadele 2019). Although little scientific research has been done on most orphan crops, a limited number of them have enjoyed advanced studies. This has mainly been due to committed scientists and institutions in developing countries as well as financial and technical support from developed nations. Most orphan crops are resilient to extreme environmental conditions. Due to this adaptability to marginal and low input environments, orphan crops offer opportunities for low greenhouse gas emissions (Mabhaudhi et al. 2019). In addition, these indigenous crops provide nutrient-rich biodiversity and healthier diets to resource-poor consumers (Hunter et al. 2019). Due to multiple dietary benefits and their tolerance to extreme environmental conditions, some orphan crops are considered to be crops for the future

Enzymes and Metabolites in Carbohydrate Metabolism of Desiccation Tolerant Plants

Resurrection plants can tolerate extreme water loss. Substantial sugar accumulation is a phenomenon in resurrection plants during dehydration. Sugars have been identified as one important factor contributing to desiccation tolerance. Phylogenetic diversity of resurrection plants reflects the diversity of sugar metabolism in response to dehydration. Sugars, which accumulate during dehydration, have been shown to protect macromolecules and membranes and to scavenge reactive oxygen species. This review focuses on the performance of enzymes participating in sugar metabolism during dehydration stress. The relation between sugar metabolism and other biochemical activities is discussed and open questions as well as potential experimental approaches are proposed

The role of small RNAs in abiotic stress

AbstractIt was recently discovered that plants respond to environmental stress not only with a specific gene expression programme at the mRNA and protein level but also small RNAs as response modulators play an important role. The small RNAs lead to cleavage or translational inhibition of mRNAs via complementary target sites. Different examples are described where small RNAs have been shown to be involved in stress responses. A link between hormonal action and small RNA activities has frequently been observed thus coupling exogenous factors with endogenous transmitters. Using the CDT-1 gene from the desiccation tolerant plant Craterostigma plantagineum as an example, it is discussed that generation of novel small RNAs could be an evolutionary pathway in plants to adapt to extreme environments