Insights into the cellular mechanisms of desiccation tolerance among angiosperm resurrection plant species

ABSTRACT Water is a major limiting factor in growth and reproduction in plants. The ability of tissues to survive desiccation is commonly found in seeds or pollen but rarely present in vegetative tissues. Resurrection plants are remarkable as they can tolerate almost complete water loss from their vegetative tissues such as leaves and roots. Metabolism is shut down as they dehydrate and the plants become apparently lifeless. Upon rehydration these plants recover full metabolic competence and 'resurrect'. In order to cope with desiccation, resurrection plants have to overcome a number of stresses as water is lost from the cells, among them oxidative stress, destabilization or loss of membrane integrity and mechanical stress. This review will mainly focus on the effect of dehydration in angiosperm resurrection plants and some of the strategies developed by these plants to tolerate desiccation. Resurrection plants are important experimental models and understanding the physiological and molecular aspects of their desiccation tolerance is of great interest for developing drought-tolerant crop species adapted to semi-arid areas

Cell wall characteristics and structure of hydrated and dry leaves of the resurrection plant Craterostigma wilmsii, a microscopical study.

The cell wall architecture of leaf tissues of the resurrection plant Craterostigma wilmsii at various stages of dehydration and rehydration was studied using electron microscopy and immunocytochemistry with antibodies to a hemicellulose (xyloglucan) and pectins. Upon dehydration, the cell walls were shown to fold extensively. It is thought that this folding may prevent excessive mechanical stress developing between the cell wall and the plasmalemma. Our immunocytochemical results show a significant increase in labelling of xyloglucan and unesterified pectins in the cell wall during drying, with levels declining again during rehydration. These components are known to play an important structural role within the cell wall, giving it more tensile strength. It is hypothesised that this increase in tensile strength allows the cell wall to contract and then fold as the plant dries and ultimately prevents the total inward collapse of the cell walls in dry tissue. The increased tensile strength may also be necessary to prevent the cell wall from unfolding and expanding too rapidly upon rehydration, thus allowing plasmalemma-cell wall connections to be reestablished

Are cell wall arabinoxylans involved in desiccation tolerance of the South African resurrection grass Eragrostis nindensis

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Structural characterization of arabinoxylans from two African plant species Eragrostis nindensis and Eragrostis tef using various mass spectrometric methods

International audienceRATIONALE: The arabinoxylans are one of the main components of plant cell walls and are known to play major roles in plant tissues properties depending in particular on their structural features. It has been recently shown that one of the strategies developed by resurrection plants to overcome dehydration is based on cell wall composition. For this purpose, the structural characterization of arabinoxylans from desiccation-tolerant grass Eragrostis nindensis (E. nindensis) was compared with its close relative, the desiccation-sensitive Eragrostis tef (E. tef) in order to further understand mechansism of desiccation tolerance in resurrection plants. METHODS: Ion mobility spectrometry coupled to mass spectrometry (IM-MS) in combination with the conventional mass spectrometric approaches, including matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS), electrospray ionization multistage tandem mass spectrometry (ESI-MSn) and gas chromatography/mass spectrometry (GC/MS), were used to characterize arabinoxylan fragments obtained after endo-xylanase digestion of leave extracts from E. nindensis and E. tef. RESULTSWhole fingerprinting by MALDI-MS analysis showed the presence of various arabinoxylan fragments within leaves of E. nindensis and E. tef. The monosaccharide composition and some linkage information were determined by GC/MS experiments. Information regarding the branching and sequence details was obtained by ESI-MSn experiments after sample permethylation. The presence of structural isomeric ions with different collision cross sections was evidenced by IM-MS which could be differentiated using ESI-MSn. CONCLUSIONS: We have shown that an orthogonal approach, and especially IM-MS associated to ESI-MSn (n=2 to 4) and GC/MS allowed characterization of arabinoxylan fragments of E. nindensis and E. tef and revealed the presence of isomeric structures. The same arabinoxylan structures were identified for both species but in different relative abundance. Moreover, this work illustrated that IM-MS can efficiently separate isomeric structures and advantageously complements the conventional mass spectrometric methodologies used for arabinoxylan structural characterization

Plant–microbe and Plant–insect Interactions Meet Common Grounds

Plant–microbe and plant–insect interactions are of global importance for agriculture and of high interest to many plant scientists, microbiologists and entomologists. Traditionally, plant–microbe and plant–insect interactions have been looked at as two separate issues, but in recent years it has become clear that the underlying physiological pathways in plants overlap substantially (Koornneef & Pieterse, 2008). The International Conference on Biotic Plant Interactions (ICBPI; http://www.uq.edu.au/plants/icbpi/) brought together scientists and students who are interested in plant pathology and in the beneficial interactions of plants with other organisms, including viruses, bacteria, fungi, oomycetes, nematodes, insects and other herbivores. To highlight this, two topics from this year's conference – harmful biotic plant interactions, and the interactions of plants with beneficial microbial communities – are discussed in this article. '... identifying the overlapping defence mechanisms against pathogen and herbivore attack will reveal new insights into plant function and their responses to environmental pressures ...

Contributions to Arabinogalactan Protein Analysis

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