Signaling Role of Fructose Mediated by FINS1/FBP in Arabidopsis thaliana

Sugars are evolutionarily conserved signaling molecules that regulate the growth and development of both unicellular and multicellular organisms. As sugar-producing photosynthetic organisms, plants utilize glucose as one of their major signaling molecules. However, the details of other sugar signaling molecules and their regulatory factors have remained elusive, due to the complexity of the metabolite and hormone interactions that control physiological and developmental programs in plants. We combined information from a gain-of-function cell-based screen and a loss-of-function reverse-genetic analysis to demonstrate that fructose acts as a signaling molecule in Arabidopsis thaliana. Fructose signaling induced seedling developmental arrest and interacted with plant stress hormone signaling in a manner similar to that of glucose. For fructose signaling responses, the plant glucose sensor HEXOKINASE1 (HXK1) was dispensable, while FRUCTOSE INSENSITIVE1 (FINS1), a putative FRUCTOSE-1,6-BISPHOSPHATASE, played a crucial role. Interestingly, FINS1 function in fructose signaling appeared to be independent of its catalytic activity in sugar metabolism. Genetic analysis further indicated that FINS1–dependent fructose signaling may act downstream of the abscisic acid pathway, in spite of the fact that HXK1–dependent glucose signaling works upstream of hormone synthesis. Our findings revealed that multiple layers of controls by fructose, glucose, and abscisic acid finely tune the plant autotrophic transition and modulate early seedling establishment after seed germination

Regulation of the Fruit-Specific PEP Carboxylase SlPPC2 Promoter at Early Stages of Tomato Fruit Development

The SlPPC2 phosphoenolpyruvate carboxylase (PEPC; EC 4.1.1.31) gene from tomato (Solanum lycopersicum) is differentially and specifically expressed in expanding tissues of developing tomato fruit. We recently showed that a 1966 bp DNA fragment located upstream of the ATG codon of the SlPPC2 gene (GenBank AJ313434) confers appropriate fruit-specificity in transgenic tomato. In this study, we further investigated the regulation of the SlPPC2 promoter gene by analysing the SlPPC2 cis-regulating region fused to either the firefly luciferase (LUC) or the β-glucuronidase (GUS) reporter gene, using stable genetic transformation and biolistic transient expression assays in the fruit. Biolistic analyses of 5′ SlPPC2 promoter deletions fused to LUC in fruits at the 8th day after anthesis revealed that positive regulatory regions are mostly located in the distal region of the promoter. In addition, a 5′ UTR leader intron present in the 1966 bp fragment contributes to the proper temporal regulation of LUC activity during fruit development. Interestingly, the SlPPC2 promoter responds to hormones (ethylene) and metabolites (sugars) regulating fruit growth and metabolism. When tested by transient expression assays, the chimeric promoter:LUC fusion constructs allowed gene expression in both fruit and leaf, suggesting that integration into the chromatin is required for fruit-specificity. These results clearly demonstrate that SlPPC2 gene is under tight transcriptional regulation in the developing fruit and that its promoter can be employed to drive transgene expression specifically during the cell expansion stage of tomato fruit. Taken together, the SlPPC2 promoter offers great potential as a candidate for driving transgene expression specifically in developing tomato fruit from various tomato cultivars

Deepening into the proteome of maize cells habituated to the cellulose biosynthesis inhibitor dichlobenil

Cellulose biosynthesis inhibitors, such as dichlobenil (DCB), have become a valuable tool for the analysis of structural and compositional plasticity of plant cell walls. By stepwise increasing the concentration of DCB in the culture medium, we obtained maize cells able to cope with DCB through the acquisition of a modified cell wall in which cellulose was partially replaced by a more extensive network of feruloylated arabinoxylans. Recently we demonstrated that the expression of several Cellulose Synthase and phenylpropanoid-related genes is altered in DCB-habituated cells. In addition, by using a proteomic approach we identified several proteins induced or repressed in DCB-habituated cells. After a more in-depth analysis, some new proteins induced (two inhibitors TAXI-IV, an α-1,4-glucan-protein synthase and a pectinesterase inhibitor) or repressed (a chaperonin 60, a fructokinase-1 and a spermidine synthase 1) were identified, and their possible role in the context of DCB-habituation is discussed

Changes in the abundance of sugars and sugar-like compounds in tall fescue (Festuca arundinacea) due to growth in naphthalene-treated sand

The hydrophilic metabolome of tall fescue (Festuca arundinacea) adapted to grow in naphthalene-treated sand (0.8 g kg−1 sand dw) was analysed using gas chromatography-mass spectrometry, and peaks corresponding to the more abundant compounds were tentatively identified from analysis of their mass spectral features and reference to the NIST Mass Spectral Database. Particular attention was paid to sugars as they are known to play important roles as stress regulators in plants. The results showed that the abundance of sugars was greater in the roots but lesser in the shoots of treated plants when compared to their control counterparts. The results for indole acetic acid (IAA) were notable: IAA was prominently less in the treated roots compared to shoots, and in treated shoots, IAA was particularly subdued compared to untreated shoots consistent with IAA degradation in treated plant tissues. The differences in the molecular phenotype between control and treated plants were expressed in root structural differences. The treated roots were modified to have greater suberisation, enhanced thickening in the endodermis and distortions in the cortical zone as demonstrated through scanning electron and epi-fluorescence microscopy