The water status of plant leaves depends on the efficiency of the water supply, from the vasculature to inner tissues. This process is under hormonal and environmental regulation and involves aquaporin water channels. In Arabidopsis thaliana, the rosette hydraulic conductivity (K ros ) is higher in darkness than it is during the day. Knockout plants showed that three plasma membrane intrinsic proteins (PIPs) sharing expression in veins (PIP1;2, PIP2;1, and PIP2;6) contribute to rosette water transport, and PIP2;1 can fully account for K ros responsiveness to darkness. Directed expression of PIP2;1 in veins of a pip2;1 mutant was sufficient to restore K ros . In addition, a positive correlation, in both wild-type and PIP2;1-overexpressing plants, was found between K ros and the osmotic water permeability of protoplasts from the veins but not from the mesophyll. Thus, living cells in veins form a major hydraulic resistance in leaves. Quantitative proteomic analyses showed that light-dependent regulation of K ros is linked to diphosphorylation of PIP2;1 at Ser-280 and Ser-283. Expression in pip2;1 of phosphomimetic and phosphorylation-deficient forms of PIP2;1 demonstrated that phosphorylation at these two sites is necessary for K ros enhancement under darkness. These findings establish how regulation of a single aquaporin isoform in leaf veins critically determines leaf hydraulics.

BACKGROUND:The effect of photodamage on facial stratum corneum (SC) is still poorly understood. OBJECTIVE: To describe the SC proteome from tape strippings of Caucasian SC from photoexposed cheek and photoprotected postauricular (PA) site, a global analysis of photodamage on the skin will be developed leading to a better understanding of keratinocyte signalling pathways and identification of new molecular targets for the treatment of photoaged skin. METHODS: Female Caucasian subjects had nine consecutive tape strippings taken from their cheeks and PA site. Proteins were extracted and the trypsin-digested peptides were analysed by nanochromatography coupled to a high-resolution mass spectrometer. Data-dependent acquisition allowed protein identification that was processed by Paragon algorithm of Protein Pilot software. RESULTS: Changes in the levels of epidermal differentiation proteins were apparent indicating poor epidermal differentiation and SC maturation (keratins, cornified envelope (CE) proteins) on photoexposed cheeks. Differences in protease-anti-protease balance were observed for corneodesmolysis (favouring desquamation) and filaggrinolysis (favouring reduced filaggrin processing). 12R-LOX, a CE maturation enzyme, was reduced in photodamaged skin but not transglutaminases. Changes in signal keratinocyte transduction pathway markers were demonstrated especially by reduced levels of downstream signalling markers such as calreticulin (unfolded protein response; UPR) and increased level of stratifin (target of rapamycin; mTOR). Evidence for impaired proteostasis was apparent by reduced levels of a key proteasomal subunit (subunit beta type-6). Finally, key antioxidant proteins were upregulated except catalase. CONCLUSION: Clear examples of poor keratinocyte differentiation and associated metabolic and signalling pathways together with reduced SC maturation were identified in photodamaged facial SC. Corneocyte immaturity was evident with changes in CE proteins. Particularly, the reduction in 12R-LOX is a novel finding in photodamaged skin and supports the lack of SC maturation. Moreover, filaggrinolysis was reduced, whereas corneodesmolysis was enhanced. From our results, we propose that there is a poor crosstalk between the keratinocyte endoplasmic reticulum UPR, proteasome network and autophagy machinery that possibly leads to impaired keratinocyte proteostasis. Superimposed on these aberrations is an apparently enhanced mTOR pathway that also contributes to reduced SC formation and maturation. Our results clearly indicate a corneocyte scaffold disorder in photodamaged cheek SC.R esum e CONTEXTE: Les effets des dommages dus a l'exposition a la lumiere sur le stratum corneum (SC) sont encore mal compris. OBJECTIFS: D ecrire le prot eome du SC issu de pr el evements par bandes adh esives provenant de la joue, expos ee a la lumi ere, et de la r egion post-auriculaire, prot eg ee de la lumi ere, de sujets caucasiens.A cette fin, une analyse globale des dommages cutan es dus a l'exposition a la lumi er...

Plant membranes bear a variety of transporters belonging to multigene families that are affected by environmental and nutritional conditions. In addition, they often display high-sequence identity, making difficult in-depth investigation by current shot-gun strategies. In this study, we set up a targeted proteomics approach aimed at identifying and quantifying within single experiments the five major proton pumps of the autoinhibited H(+) ATPases (AHA) family, the 13 plasma membrane intrinsic proteins (PIP) water channels (PIPs), and ten members of ammonium transporters (AMTs) and nitrate transporter (NRT) families. Proteotypic peptides were selected and isotopically labeled heavy versions were used for technical optimization and for quantification of the corresponding light version in biological samples. This approach allowed to quantify simultaneously nine PIPs in leaf membranes and 13 PIPs together with three autoinhibited H(+) ATPases, two ammonium transporters, and two NRTs in root membranes. Similarly, it was used to investigate the effect of a salt stress on the expression of these latter 20 transporters in roots. These novel isoform-specific data were compared with published transcriptome information and revealed a close correlation between PIP isoforms and transcripts levels. The obtained resource is reusable and can be expanded to other transporter families for large-scale profiling of membrane transporters.

IntroductionWe report on the preparation and efficacy of 10‐hydroxystearic acid (HSA) that improves facial age spots and conspicuous pores.MethodsThe hydration of oleic acid into HSA was catalyzed by the oleate hydratase from Escherichia coli. Following treatment with HSA, collagen type I and type III was assessed in primary human dermal fibroblasts together with collagen type III, p53 protein levels and sunburn cells (SBC) after UVB irradiation (1 J cm−2) by immunohistochemistry on human ex vivo skin. UVB‐induced expression of matrix metalloprotease‐1 (MMP‐1) was determined from full thickness skin by RT‐qPCR. Modification of the fibroblast secretome by HSA was studied by mass‐spectrometry‐based proteomics. In a full‐face, double blind, vehicle‐controlled trial HSA was assessed for its effects on conspicuous facial pore size and degree of pigmentation of age spots in Caucasian women over an 8‐week period.ResultsHSA was obtained in enantiomeric pure, high yield (≥80%). Collagen type I and type III levels were dose‐dependently increased (96% and 244%; P < 0.01) in vitro and collagen type III in ex vivo skin by +57% (P < 0.01) by HSA. HSA also inhibited UVB‐induced MMP‐1 gene expression (83%; P < 0.01) and mitigated SBC induction (−34% vs. vehicle control) and reduced significantly UV‐induced p53 up‐regulation (−46% vs. vehicle control; P < 0.01) in irradiated skin. HSA modified the fibroblast secretome with significant increases in proteins associated with the WNT pathway that could reduce melanogenesis and proteins that could modify dermal fibroblast activity and keratinocyte differentiation to account for the alleviation of conspicuous pores. Docking studies in silico and EC50 determination in reporter gene assays (EC50 5.5 × 10−6 M) identified HSA as a peroxisomal proliferator activated receptor‐α (PPARα) agonist. Clinically, HSA showed a statistically significant decrease of surface and volume of skin pores (P < 0.05) after 8 weeks of application and age spots became significantly less pigmented than the surrounding skin (contrast, P < 0.05) after 4 weeks.ConclusionHSA acts as a PPARα agonist to reduce the signs of age spots and conspicuous pores by significantly modulating the expression of p53, SBC, MMP‐1 and collagen together with major changes in secreted proteins that modify keratinocyte, melanocyte and fibroblast cell behavior.

Crustacean shellfish allergy ranks among the most frequent and severe food allergies for adults, demanding rugged and sensitive analytical routine methods. The objective of this study was therefore to develop a mass spectrometric approach for the detection of contamination with shrimp and lobster, two economically important types of crustaceans, in complex food matrices. Following a biomarker approach, we identified proteotypic peptides and developed a multiple reaction monitoring (MRM) method allowing for the identification and differentiation of shrimp and lobster in the food matrix at concentrations down to 0.1%. To further enhance sensitivity, we employed the MRM-cubed (MRM(3)) mode, which allowed us to detect crustaceans down to concentrations of 25 μg/g (crustacean/food, 0.0025%). We hereby present the first mass spectrometric method for the detection of shrimp and lobster in food matrices.