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Salt stress is a major abiotic stress, responsible for declining agricultural productivity. Roots are regarded as hubs for salt detoxification, however, leaf salt concentrations may exceed those of roots. How mature leaves manage acute sodium chloride (NaCl) stress is mostly unknown. To analyze the mechanisms for NaCl redistribution in leaves, salt was infiltrated into intact tobacco leaves. It initiated pronounced osmotically‐driven leaf movements. Leaf downward movement caused by hydro‐passive turgor loss reached a maximum within 2 h. Salt‐driven cellular water release was accompanied by a transient change in membrane depolarization but not an increase in cytosolic calcium ion (Ca\(^{2+}\)) level. Nonetheless, only half an hour later, the leaves had completely regained turgor. This recovery phase was characterized by an increase in mesophyll cell plasma membrane hydrogen ion (H\(^{+}\)) pumping, a salt uptake‐dependent cytosolic alkalization, and a return of the apoplast osmolality to pre‐stress levels. Although, transcript numbers of abscisic acid‐ and Salt Overly Sensitive pathway elements remained unchanged, salt adaptation depended on the vacuolar H\(^{+}\)/Na\(^{+}\)‐exchanger NHX1. Altogether, tobacco leaves can detoxify sodium ions (Na\(^{+}\)) rapidly even under massive salt loads, based on pre‐established posttranslational settings and NHX1 cation/H+ antiport activity. Unlike roots, signaling and processing of salt stress in tobacco leaves does not depend on Ca\(^{2+}\) signaling. more...

SummaryBacterial regulatory RNAs (sRNAs) have been implicated in the regulation of numerous metabolic pathways. In most of these studies, sRNA-dependent regulation of mRNAs or proteins of enzymes in metabolic pathways has been predicted to affect the metabolism of these bacteria. However, only in very few cases has the role in metabolism been demonstrated. We performed here a combined transcriptome and metabolome analysis to define the regulon of the sibling sRNAs NgncR_162 and NgncR_163 and their impact on the metabolism of the major human pathogen Neisseria gonorrhoeae. These sRNA have previously been shown to control genes of the citric acid and methylcitrate cycle by post-transcriptional negative regulation. By transcriptome analysis we expand the NgncR_162/163 regulon by several new members and provide evidence that the sibling sRNAs act as both negative and positive regulators of target gene expression. Newly identified NgncR_162/163 targets are mostly involved in transport processes, especially the uptake of glycine, branched chain amino acids and phenylalanine. NgncR_162/163 also play key roles in the control of serine-glycine metabolism and hence probably affect biosynthesis of nucleotides, vitamins and other amino acids via the supply of C1-units. Metabolic flux analysis demonstrated a bipartite metabolism with glucose degradation providing intermediates for anabolic pathways, while energy metabolism via the citric acid cycle is mainly driven by amino acids, which feed into the cycle. Thus, by combined RNA-seq and metabolomics we significantly extended the regulon of NgncR_162/163 and demonstrate their role in the regulation of central metabolic pathways of the gonococcus.ImportanceNeisseria gonorrhoeae is a major human pathogen which infects more than 100 million people every year. An alarming development is the emergence of gonococcal strains resistant against virtually all of the antibiotics used for their treatment. Despite the medical importance and the vanishing treatment options of gonococcal infections, the bacterial metabolism and its regulation is only ill defined until today. We investigate here the regulation of the gonococcal metabolism by two previously studied sRNAs, NgncR_162/163 using RNA-seq and metabolomics. The results provided in this study demonstrate the regulation of transport processes and metabolic pathways involved in the biosynthesis of nucleotides, vitamins and amino acids by NgncR_162/163. Combined transcriptome and metabolome analyses provide a thus far unreached depth in the regulation of metabolic pathways by the neisserial sibling sRNAs and may therefore also be suitable for functional analysis of a growing number of other bacterial metabolic sRNA regulators. more...

The onset of plant life is characterized by a major phase transition. During early heterotrophic seedling establishment, seed storage reserves fuel metabolic demands, allowing the plant to switch to autotrophic metabolism. Although metabolic pathways leading to storage compound mobilization are well-described, the regulatory circuits remain largely unresolved. Using an inducible knockdown approach of the evolutionarily conserved energy master regulator Snf1-RELATED-PROTEIN-KINASE1 (SnRK1), phenotypic studies reveal its crucial function in Arabidopsis thaliana seedling establishment. Importantly, glucose feeding largely restores growth defects of the kinase mutant, supporting its major impact in resource mobilization. Detailed metabolite studies reveal sucrose as a primary resource early in seedling establishment, in a SnRK1-independent manner. Later, SnRK1 orchestrates catabolism of triacylglycerols and amino acids. Concurrent transcriptomic studies highlight SnRK1 functions in controlling metabolic hubs fuelling gluconeogenesis, as exemplified by cytosolic PYRUVATE ORTHOPHOSPHATE DIKINASE (cyPPDK). Here, SnRK1 establishes its function via phosphorylation of the transcription factor BASIC LEUCINE ZIPPER63 (bZIP63), which directly targets and activates the cyPPDK promoter. Taken together, our results disclose developmental and catabolic functions of SnRK1 in seed storage mobilization and describe a prototypic gene regulatory mechanism. As seedling establishment is important for plant vigor and crop yield, our findings are of agronomical importance. more...

Plant architecture is highly plastic and known to respond sensitively to nutritional changes. Although of great agronomic importance, the underlying molecular mechanisms that sense and transduce these cues into plant development and growth are poorly understood. Applying diverse genetic, biochemical, and microscopic approaches, we disclosed that signaling via the central, evolutionarily conserved fuel-sensor kinase Snf1-RELATED KINASE1 (SnRK1) initiates lateral root (LR) primordia formation in response to transient metabolic perturbations. This is accomplished by SnRK1-mediated activation of a signaling cascade involving the pivotal LR regulator AUXIN RESPONSE FACTOR19 (ARF19). We propose that this developmental priming strategy represents a cost-efficient approach to ensure rapid growth recovery after stress release, providing in competitive ecosystems a clear advantage in terms of Darwinian fitness.Plants adjust their energy metabolism to continuous environmental fluctuations, resulting in a tremendous plasticity in their architecture. The regulatory circuits involved, however, remain largely unresolved. In Arabidopsis, moderate perturbations in photosynthetic activity, administered by short-term low light exposure or unexpected darkness, lead to increased lateral root (LR) initiation. Consistent with expression of low-energy markers, these treatments alter energy homeostasis and reduce sugar availability in roots. Here, we demonstrate that the LR response requires the metabolic stress sensor kinase Snf1-RELATED-KINASE1 (SnRK1), which phosphorylates the transcription factor BASIC LEUCINE ZIPPER63 (bZIP63) that directly binds and activates the promoter of AUXIN RESPONSE FACTOR19 (ARF19), a key regulator of LR initiation. Consistently, starvation-induced ARF19 transcription is impaired in bzip63 mutants. This study highlights a positive developmental function of SnRK1. During energy limitation, LRs are initiated and primed for outgrowth upon recovery. Hence, this study provides mechanistic insights into how energy shapes the agronomically important root system.All study data are included in the article and/or supporting information. more...

Herbivore-induced plant defences influence the behaviour of insects associated with the plant. For biting–chewing herbivores the octadecanoid signal-transduction pathway has been suggested to play a key role in induced plant defence. To test this hypothesis in our plant—herbivore—parasitoid tritrophic system, we used phenidone, an inhibitor of the enzyme lipoxygenase (LOX), that catalyses the initial step in the octadecanoid pathway. Phenidone treatment of Brussels sprouts plants reduced the accumulation of internal signalling compounds in the octadecanoid pathway downstream of the step catalysed by LOX, i.e. 12-oxo-phytodienoic acid (OPDA) and jasmonic acid. The attraction of Cotesia glomerata parasitoids to host-infested plants was significantly reduced by phenidone treatment. The three herbivores investigated, i.e. the specialists Plutella xylostella, Pieris brassicae and Pieris rapae, showed different oviposition preferences for intact and infested plants, and for two species their preference for either intact or infested plants was shown to be LOX dependent. Our results show that phenidone inhibits the LOX-dependent defence response of the plant and that this inhibition can influence the behaviour of members of the associated insect community. more...

The commercially used cell suspension culture of COPTIS JAPONICA Makino (Ranunculaceae) incorporates [beta- (13)C]tyrosine into both halves of the berberine molecule (isoquinoline and benzyl portion) while L-[3'- (18)O]DOPA only labels the isoquinoline portion of this molecule. This labelling pattern indicates that different C (6)-C (2) units derived from tyrosine form this molecule. This result and the incorporation of ( S)-[1- (13)C] norcoclaurine into berberine demonstrates that the biosynthesis of protoberberine alkaloids in COPTIS involves the norcoclaurine but not the norlaudanosoline pathway. more...