Aquaporins facilitate the uptake of soil water and mediate the regulation of root hydraulic conductivity (Lp r ) in response to a large variety of environmental stresses. Here, we use Arabidopsis (Arabidopsis thaliana) plants to dissect the effects of salt on both Lp r and aquaporin expression and investigate possible molecular and cellular mechanisms of aquaporin regulation in plant roots under stress. Treatment of plants by 100 mM NaCl was perceived as an osmotic stimulus and induced a rapid (halftime, 45 min) and significant (70%) decrease in Lp r , which was maintained for at least 24 h. Macroarray experiments with genespecific tags were performed to investigate the expression of all 35 genes of the Arabidopsis aquaporin family. Transcripts from 20 individual aquaporin genes, most of which encoded members of the plasma membrane intrinsic protein (PIP) and tonoplast intrinsic protein (TIP) subfamilies, were detected in nontreated roots. All PIP and TIP aquaporin transcripts with a strong expression signal showed a 60% to 75% decrease in their abundance between 2 and 4 h following exposure to salt. The use of antipeptide antibodies that cross-reacted with isoforms of specific aquaporin subclasses revealed that the abundance of PIP1s decreased by 40% as early as 30 min after salt exposure, whereas PIP2 and TIP1 homologs showed a 20% to 40% decrease in abundance after 6 h of treatment. Expression in transgenic plants of aquaporins fused to the green fluorescent protein revealed that the subcellular localization of TIP2;1 and PIP1 and PIP2 homologs was unchanged after 45 min of exposure to salt, whereas a TIP1;1-green fluorescent protein fusion was relocalized into intracellular spherical structures tentatively identified as intravacuolar invaginations. The appearance of intracellular structures containing PIP1 and PIP2 homologs was occasionally observed after 2 h of salt treatment. In conclusion, this work shows that exposure of roots to salt induces changes in aquaporin expression at multiple levels. These changes include a coordinated transcriptional down-regulation and subcellular relocalization of both PIPs and TIPs. These mechanisms may act in concert to regulate root water transport, mostly in the long term ($6 h).Soil salinity exerts noxious effects on plants and causes a significant drop in yield for crop production in 7% of arable land worldwide, including the majority of irrigated lands (Hasegawa et al., 2000;Halperin et al., 2003;Zhu, 2003). In particular, exposure to salinity challenges the plant water status and triggers specific strategies for cell osmotic adjustment and control of water uptake and loss (Hasegawa et al., 2000;Fricke and Peters, 2002). One of the primary responses of plants to salt is inhibition of their root water uptake capacity (i.e. root hydraulic conductivity [Lp r ]). Although notable exceptions have been reported in barley (Hordeum vulgare;Munns and Passioura, 1984) and tobacco (Nicotiana tabacum;Tyerman et al., 1989), this response can be observed in a large variety of glyco...

Next-generation electronics (e.g., substrate and conductor) need to be high performance, multifunctional, and environmentally friendly. Here, we report the creation of a fully wood-based flexible electronics circuit meeting these requirements, where the substrate, a strong, flexible and transparent wood film, is printed with a lignin-derived carbon nanofibers conductive ink. The wood film fabrication involves extensive removal of lignin and hemicellulose to tailor the nanostructure of the material followed by collapsing of the cell walls. This process preserves the original alignment of the cellulose nanofibers and promotes their binding. The film is flexible, yet strong in fiber direction with a Young’s modulus and a tensile strength of 49.9 GPa and 469.9 MPa, respectively. Furthermore, a sustainable and bio-based conductive ink is formulated with lignin-derived carbon nanofibers. The bio-based ink is printed on transparent wood film, and a strain sensor application of the printed circuit is demonstrated. Combining the transparent wood film with the conductive ink produces environmental friendly and sustainable wood-based electronics for potential applications such as flexible circuits and sensors. Moreover, we envision the potential for a scalable and continuous fabrication process as well as end-of-life recyclability.

We have mapped the expression of the tonoplast intrinsic protein (TIP) gene family members in Arabidopsis seeds by fluorescent protein tagging of their genomic sequences and confocal microscopy. Three isoforms (TIP1;1, TIP2;1, and TIP2;2) have distinct patterns of expression in maternal tissues (outer integument and placento-chalazal region). Two isoforms, TIP3;1 and the previously uncharacterized TIP3;2, are the only detectable TIPs in embryos during seed maturation and the early stages of seed germination. Throughout these developmental stages, both isoforms co-locate to the tonoplast of the protein storage vacuoles, but also appear to label the plasma membrane. Plasma membrane labeling is specific to TIP3;1 and TIP3;2, is independent of the position of the fluorescent protein tag, and appears to be specific to early seed maturation and early germination stages. We discuss these results in the context of the predicted distribution of aquaporins in Arabidopsis seeds.

SUMMARYThe constitutive cycling of plant plasma membrane (PM) proteins is an essential component of their function and regulation under resting or stress conditions. Transgenic Arabidopsis plants that express GFP fusions with AtPIP1;2 and AtPIP2;1, two prototypic PM aquaporins, were used to develop a fluorescence recovery after photobleaching (FRAP) approach. This technique was used to discriminate between PM and endosomal pools of the aquaporin constructs, and to estimate their cycling between intracellular compartments and the cell surface. The membrane trafficking inhibitors tyrphostin A23, naphthalene-1-acetic acid and brefeldin A blocked the latter process. By contrast, a salt treatment (100 mM NaCl for 30 min) markedly enhanced the cycling of the aquaporin constructs and modified their pharmacological inhibition profile. Two distinct models for PM aquaporin cycling in resting or salt-stressed root cells are discussed.