Compartmentation is a key strategy enacted by plants for the storage of specialized metabolites. The saffron spice owes its red color to crocins, a complex mixture of apocarotenoid glycosides that accumulate in intracellular vacuoles and reach up to 10% of the spice dry weight. We developed a general approach, based on coexpression analysis, heterologous expression in yeast (Saccharomyces cerevisiae), and in vitro transportomic assays using yeast microsomes and total plant metabolite extracts, for the identification of putative vacuolar metabolite transporters, and we used it to identify Crocus sativus transporters mediating vacuolar crocin accumulation in stigmas. Three transporters, belonging to both the multidrug and toxic compound extrusion and ATP binding cassette C (ABCC) families, were coexpressed with crocins and/or with the gene encoding the first dedicated enzyme in the crocin biosynthetic pathway, CsCCD2. Two of these, belonging to the ABCC family, were able to mediate transport of several crocins when expressed in yeast microsomes. CsABCC4a was selectively expressed in C. sativus stigmas, was predominantly tonoplast localized, transported crocins in vitro in a stereospecific and cooperative way, and was able to enhance crocin accumulation when expressed in Nicotiana benthamiana leaves.

Interfering with leucine biosynthesis affects the TOR network and causes changes in cell growth that lead to suppression of the cell wall formation mutant lrx1 .

The plant vacuole is a cellular compartment that is essential to plant development and growth. Often plant vacuoles accumulate specialized metabolites, also called secondary metabolites, which constitute functionally and chemically diverse compounds that exert in planta many essential functions and improve the plant's fitness. These metabolites provide, for example, chemical defense against herbivorous and pathogens or chemical attractants (color and fragrance) to attract pollinators. The chemical composition of the vacuole is dynamic, and is altered during development and as a response to environmental changes. To some extent these alterations rely on vacuolar transporters, which import and export compounds into and out of the vacuole, respectively. During the past decade, significant progress was made in the identification and functional characterization of the transporters implicated in many aspects of plant specialized metabolism. Still, deciphering the molecular players underlying such processes remains a challenge for the future. In this review, we present a comprehensive summary of the most recent achievements in this field.

Tomato landraces, originated by adaptive responses to local habitats, are considered a valuable resource for many traits of agronomic interest, including fruit nutritional quality. Primary and secondary metabolites are essential determinants of fruit organoleptic quality, and some of them, such as carotenoids and phenolics, have been associated with beneficial proprieties for human health. Landraces’ fruit taste and flavour are often preferred by consumers compared to the commercial varieties’ ones. In an autumn-winter greenhouse hydroponic experiment, the response of three Southern-Italy tomato landraces (Ciettaicale, Linosa and Corleone) and one commercial cultivar (UC-82B) to different concentrations of sodium chloride (0 mM, 60 mM or 120 mM NaCl) were evaluated. At harvest, no losses in marketable yield were noticed in any of the tested genotypes. However, under salt stress, fresh fruit yield as well as fruit calcium concentration were higher affected in the commercial cultivar than in the landraces. Furthermore, UC-82B showed a trend of decreasing lycopene and total antioxidant capacity with increasing salt concentration, whereas no changes in these parameters were observed in the landraces under 60 mM NaCl. Landraces under 120 mM NaCl accumulated more fructose and glucose in the fruits, while salt did not affect hexoses levels in UC-82B. Ultra-performance liquid chromatography–tandem mass spectrometry analysis revealed differential accumulation of glycoalkaloids, phenolic acids, flavonoids and their derivatives in the fruits of all genotypes under stress. Overall, the investigated Italian landraces showed a different behaviour compared to the commercial variety UC-82B under moderate salinity stress, showing a tolerable compromise between yield and quality attributes. Our results point to the feasible use of tomato landraces as a target to select interesting genetic traits to improve fruit quality under stress conditions.

Summary Strigolactones (SLs) are carotenoid‐derived phytohormones shaping plant architecture and inducing the symbiosis with endomycorrhizal fungi. In Petunia hybrida, SL transport within the plant and towards the rhizosphere is driven by the ABCG‐class protein PDR1. PDR1 expression is regulated by phytohormones and by the soil phosphate abundance, and thus SL transport integrates plant development with nutrient conditions.We overexpressed PDR1 (PDR1 OE) to investigate whether increased endogenous SL transport is sufficient to improve plant nutrition and productivity. Phosphorus quantification and nondestructive X‐ray computed tomography were applied. Morphological and gene expression changes were quantified at cellular and whole tissue levels via time‐lapse microscopy and quantitative PCR. PDR1 OE significantly enhanced phosphate uptake and plant biomass production on phosphate‐poor soils. PDR1 OE plants showed increased lateral root formation, extended root hair elongation, faster mycorrhization and reduced leaf senescence. PDR1 overexpression allowed considerable SL biosynthesis by releasing SL biosynthetic genes from an SL‐dependent negative feedback.The increased endogenous SL transport/biosynthesis in PDR1 OE plants is a powerful tool to improve plant growth on phosphate‐poor soils. We propose PDR1 as an as yet unexplored trait to be investigated for crop production. The overexpression of PDR1 is a valuable strategy to investigate SL functions and transport routes.

Bialaphos resistance (BAR) and phosphinothricin acetyltransferase (PAT) genes, which convey resistance to the broad-spectrum herbicide phosphinothricin (also known as glufosinate) via N-acetylation, have been globally used in basic plant research and genetically engineered crops . Although early in vitro enzyme assays showed that recombinant BAR and PAT exhibit substrate preference toward phosphinothricin over the 20 proteinogenic amino acids , indirect effects of BAR-containing transgenes in planta, including modified amino acid levels, have been seen but without the identification of their direct causes . Combining metabolomics, plant genetics and biochemical approaches, we show that transgenic BAR indeed converts two plant endogenous amino acids, aminoadipate and tryptophan, to their respective N-acetylated products in several plant species. We report the crystal structures of BAR, and further delineate structural basis for its substrate selectivity and catalytic mechanism. Through structure-guided protein engineering, we generated several BAR variants that display significantly reduced non-specific activities compared with its wild-type counterpart in vivo. The transgenic expression of enzymes can result in unintended off-target metabolism arising from enzyme promiscuity. Understanding such phenomena at the mechanistic level can facilitate the design of maximally insulated systems featuring heterologously expressed enzymes.

Plant hormones regulate a myriad of plant processes, from seed germination to reproduction, from complex organ development to microelement uptake. Much has been discovered on the factors regulating the activity of phytohormones, yet there are gaps in knowledge about their metabolism, signaling as well as transport. In this review we analyze the potential of the characterized phytohormonal transporters belonging to the ATP-Binding Cassette family (ABC proteins), thus to identify new candidate orthologs in model plants and species important for human health and food production. Previous attempts with phylogenetic analyses on transporters belonging to the ABC family suggested that sequence homology per se is not a powerful tool for functional characterization. However, we show here that sequence homology might indeed support functional conservation of characterized members of different classes of ABC proteins in several plant species, e.g., in the case of ABC class G transporters of strigolactones and ABC class B transporters of auxinic compounds. Also for the low-affinity, vacuolar abscisic acid (ABA) transporters belonging to the ABCC class we show that localization-, rather than functional-clustering occurs, possibly because of sequence conservation for targeting the tonoplast. The ABC proteins involved in pathogen defense are phylogenetically neighboring despite the different substrate identities, suggesting that sequence conservation might play a role in their activation/induction after pathogen attack. Last but not least, in case of the multiple lipid transporters belong to different ABC classes, we focused on ABC class D proteins, reported to transport/affect the synthesis of hormonal precursors. Based on these results, we propose that phylogenetic approaches followed by transport bioassays and in vivo investigations might accelerate the discovery of new hormonal transport routes and allow the designing of transgenic and genome editing approaches, aimed to improve our knowledge on plant development, plant–microbe symbioses, plant nutrient uptake and plant stress resistance.

Current Biology Vol 25 No 4 R136interesting questions. It took me about six months to realize that philosophy (as interesting as it is) wasn't going to answer any questions about how to reform education. Psychology seemed like the answer: I reasoned that understanding the mind should help one fi gure out how to change it. The problem then became the paucity of information about the mind. At that stage, psychology was just shaking off its behaviorist perspective (my fi rst publication, when I was an undergrad, was a behavioral study with rats). I didn't see any alternatives, and stuck with psychology.As it developed many years later, turning to studies of the brain opened up an entirely new way to think about education. I was an early adopter of neuroimaging techniques. Some of our studies focused on the nature of individual differences. In particular, we looked at how variations in regional brain activity predicted variations in behavior. Ultimately, my hope was that we could use such results to validate simple behavioral tests, and that those tests in turn could be used to characterize each person's 'processing profi le'. This profi le would indicate what sorts of processing a given person was good at, and what sorts of processing that person was not so good at. And, knowing this, we could fi gure out how best to help that person learn. This interest was a facet of my more general interest in the science of learning, which has deep potential applications in all walks of life.In general, my inclination towards applications has kept me alert to potential ways that basic science can be put into practical contexts, which has proven very useful.Which aspect of science, your fi eld or in general, would you wish the general public knew more about? I wish the public understood how useful basic research is. I understand the value of 'problem-driven' applied research, but fi nd it often narrow and circumscribed. Basic research provides foundations for solving problems that don't even exist yet. I wish the public could be educated to understand the value -in every sense of the term -of just understanding deeply the nature of our world and ourselves.What makes a vegetarian meal protein rich? The plant vacuole! Besides carbohydrates, plant vacuoles store proteins, especially in seeds. Leguminous crops such as lentils, peas and soybeans, as well as cereals such as wheat, rye and barley contain specialised protein storage vacuoles which keep a supply of nitrogen for seed germination. However, not all proteins stored in seeds are edible. The castor oil plant Ricinus communis, for example, stores the lectin ricin in its seed protein storage vacuoles. Ricin is lethal since it inhibits eukaryotic protein biosynthesis, even if only a few seeds are consumed.Where does a wine's bouquet come from? From A to Z a wine's bouquet comes from the plant vacuole. If you like to muse about the elegant, expressive nose of a wine, consider that the components giving taste to wine are stored in the grape berry's vacuole. Glucose and fructose are ...