Trehalose metabolism in plants Lunn, John Edward; Delorge, Ines; Figueroa, Carlos María ...
The Plant journal : for cell and molecular biology,
August 2014, Volume:
79, Issue:
4
Journal Article
Peer reviewed
Open access
Summary
Trehalose is a quantitatively important compatible solute and stress protectant in many organisms, including green algae and primitive plants. These functions have largely been replaced by ...sucrose in vascular plants, and trehalose metabolism has taken on new roles. Trehalose is a potential signal metabolite in plant interactions with pathogenic or symbiotic micro‐organisms and herbivorous insects. It is also implicated in responses to cold and salinity, and in regulation of stomatal conductance and water‐use efficiency. In plants, as in other eukaryotes and many prokaryotes, trehalose is synthesized via a phosphorylated intermediate, trehalose 6‐phosphate (Tre6P). A meta‐analysis revealed that the levels of Tre6P change in parallel with sucrose, which is the major product of photosynthesis and the main transport sugar in plants. We propose the existence of a bi‐directional network, in which Tre6P is a signal of sucrose availability and acts to maintain sucrose concentrations within an appropriate range. Tre6P influences the relative amounts of sucrose and starch that accumulate in leaves during the day, and regulates the rate of starch degradation at night to match the demand for sucrose. Mutants in Tre6P metabolism have highly pleiotropic phenotypes, showing defects in embryogenesis, leaf growth, flowering, inflorescence branching and seed set. It has been proposed that Tre6P influences plant growth and development via inhibition of the SNF1‐related protein kinase (SnRK1). However, current models conflict with some experimental data, and do not completely explain the pleiotropic phenotypes exhibited by mutants in Tre6P metabolism. Additional explanations for the diverse effects of alterations in Tre6P metabolism are discussed.
The function of trehalose metabolism in plants during growth and development has been extensively studied, mostly in the eudicot
. So far, however, not much is known about trehalose metabolism in the ...moss
. Here, we show that in
, two active trehalose-6-phosphate synthase enzymes exist, PpTPS1 and PpTPS2. Expression of both enzymes in
can complement the glucose-growth defect of the yeast
mutant. Truncation of N-terminal extension in PpTPS1 and PpTPS2 resulted in higher TPS activity and high trehalose levels, upon expression in yeast.
knockout plants were generated and analyzed in various conditions to functionally characterize these proteins.
and
knockouts displayed a lower amount of caulonema filaments and were significantly reduced in size of gametophores as compared to the wild type. These phenotypes were more pronounced in the
mutant. Caulonema formation is induced by factors such as high energy and auxins. Only high amounts of supplied energy were able to induce caulonema filaments in the
mutant. Furthermore, this mutant was less sensitive to auxins as NAA-induced caulonema development was arrested in the
mutant. In contrast, formation of caulonema filaments is repressed by cytokinins. This effect was more severe in the
and
mutants. Our results demonstrate that PpTPS1 and PpTPS2 are essential for sensing and signaling sugars and plant hormones to monitor the balance between caulonema and chloronema development.
The impact of abiotic stress on plant growth and development has been and still is a major research topic. An important pathway that has been linked to abiotic stress tolerance is the trehalose ...biosynthetic pathway. Recent findings showed that trehalose metabolism is also important for normal plant growth and development. The intermediate compound - trehalose-6-phosphate (T6P) - is now confirmed to act as a sensor for available sucrose, hereby directly influencing the type of response to the changing environmental conditions. This is possible because T6P and/or trehalose or their biosynthetic enzymes are part of complex interaction networks with other crucial hormone and sugar-induced signaling pathways, which may function at different developmental stages. Because of its effect on plant growth and development, modification of trehalose biosynthesis, either at the level of T6P synthesis, T6P hydrolysis, or trehalose hydrolysis, has been utilized to try to improve crop yield and biomass. It was shown that alteration of the amounts of either T6P and/or trehalose did result in increased stress tolerance, but also resulted in many unexpected phenotypic alterations. A main challenge is to characterize the part of the signaling pathway resulting in improved stress tolerance, without affecting the pathways resulting in the unwanted phenotypes. One such specific pathway where modification of trehalose metabolism improved stress tolerance, without any side effects, was recently obtained by overexpression of trehalase, which results in a more sensitive reaction of the stomatal guard cells and closing of the stomata under drought stress conditions. We have used the data that have been obtained from different studies to generate the optimal plant that can be constructed based on modifications of trehalose metabolism.
Trehalose metabolism is essential for normal growth and development in higher plants. It is synthesized in a two-step pathway catalysed by TPS (trehalose-6-phosphate synthase) and trehalose ...phosphatase. Arabidopsis thaliana has 11 TPS or TPS-like proteins, which belong to two distinct clades: class I (AtTPS1-AtTPS4) and class II (AtTPS5-AtTPS11). Only AtTPS1 has previously been shown to have TPS activity. A. thaliana tps1∆ mutants fail to complete embryogenesis and rescued lines have stunted growth and delayed flowering, indicating that AtTPS1 is important throughout the life cycle. In the present study, we show that expression of AtTPS2 or AtTPS4 enables the yeast tps1∆ tps2∆ mutant to grow on glucose and accumulate Tre6P (trehalose 6-phosphate) and trehalose. Class II TPS genes did not complement the yeast mutant. Thus A. thaliana has at least three catalytically active TPS isoforms, suggesting that loss of Tre6P production might not be the only reason for the growth defects of A. thaliana tps1 mutants.
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