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Publikationen - Molekulare Signalverarbeitung

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Publikation

Naumann, C.; Heisters, M.; Brandt, W.; Janitza, P.; Alfs, C.; Tang, N.; Toto Nienguesso, A.; Ziegler, J.; Imre, R.; Mechtler, K.; Dagdas, Y.; Hoehenwarter, W.; Sawers, G.; Quint, M.; Abel, S.; Bacterial-type ferroxidase tunes iron-dependent phosphate sensing during Arabidopsis root development Curr. Biol. 32, 2189-2205, (2022) DOI: 10.1016/j.cub.2022.04.005

Access to inorganic phosphate (Pi), a principal intermediate of energy and nucleotide metabolism, profoundly affects cellular activities and plant performance. In most soils, antagonistic Pi-metal interactions restrict Pi bioavailability, which guides local root development to maximize Pi interception. Growing root tips scout the essential but immobile mineral nutrient; however, the mechanisms monitoring external Pi sta-tus are unknown. Here, we show that Arabidopsis LOW PHOSPHATE ROOT 1 (LPR1), one key determinant of Fe-dependent Pi sensing in root meristems, encodes a novel ferroxidase of high substrate specificity and affinity (apparent KM ∼2 μmM Fe2+). LPR1 typifies an ancient, Fe-oxidizing multicopper protein family that evolved early upon bacterial land colonization. The ancestor of streptophyte algae and embryophytes (land plants) acquired LPR1-type ferroxidase from soil bacteria via horizontal gene transfer, a hypothesis supported by phylogenomics, homology modeling, and biochemistry. Our molecular and kinetic data on LPR1 regulation indicate that Pi-dependent Fe substrate availability determines LPR1 activity and function. Guided by the metabolic lifestyle of extant sister bacterial genera, we propose that Arabidopsis LPR1 monitors subtle concentration differentials of external Fe availability as a Pi-dependent cue to adjust root meristem maintenance via Fe redox signaling and cell wall modification. We further hypothesize that the acquisition of bacterial LPR1-type ferroxidase by embryophyte progenitors facilitated the evolution of local Pi sensing and acquisition during plant terrestrialization.
Publikation

Ibañez, C.; Delker, C.; Martinez, C.; Bürstenbinder, K.; Janitza, P.; Lippmann, R.; Ludwig, W.; Sun, H.; James, G. V.; Klecker, M.; Grossjohann, A.; Schneeberger, K.; Prat, S.; Quint, M.; Brassinosteroids Dominate Hormonal Regulation of Plant Thermomorphogenesis via BZR1 Curr. Biol. 28, 303-310.e3, (2018) DOI: 10.1016/j.cub.2017.11.077

Thermomorphogenesis is defined as the suite of morphological changes that together are likely to contribute to adaptive growth acclimation to usually elevated ambient temperature [1, 2]. While many details of warmth-induced signal transduction are still elusive, parallels to light signaling recently became obvious (reviewed in [3]). It involves photoreceptors that can also sense changes in ambient temperature [3, 4, 5] and act, for example, by repressing protein activity of the central integrator of temperature information PHYTOCHROME-INTERACTING FACTOR 4 (PIF4 [6]). In addition, PIF4 transcript accumulation is tightly controlled by the evening complex member EARLY FLOWERING 3 [7, 8]. According to the current understanding, PIF4 activates growth-promoting genes directly but also via inducing auxin biosynthesis and signaling, resulting in cell elongation. Based on a mutagenesis screen in the model plant Arabidopsis thaliana for mutants with defects in temperature-induced hypocotyl elongation, we show here that both PIF4 and auxin function depend on brassinosteroids. Genetic and pharmacological analyses place brassinosteroids downstream of PIF4 and auxin. We found that brassinosteroids act via the transcription factor BRASSINAZOLE RESISTANT 1 (BZR1), which accumulates in the nucleus at high temperature, where it induces expression of growth-promoting genes. Furthermore, we show that at elevated temperature BZR1 binds to the promoter of PIF4, inducing its expression. These findings suggest that BZR1 functions in an amplifying feedforward loop involved in PIF4 activation. Although numerous negative regulators of PIF4 have been described, we identify BZR1 here as a true temperature-dependent positive regulator of PIF4, acting as a major growth coordinator.
Publikation

Ryan, P. T.; Ó’Maoiléidigh, D. S.; Drost, H.-G.; Kwaśniewska, K.; Gabel, A.; Grosse, I.; Graciet, E.; Quint, M.; Wellmer, F.; Patterns of gene expression during Arabidopsis flower development from the time of initiation to maturation BMC Genomics 16, 488, (2015) DOI: 10.1186/s12864-015-1699-6

BackgroundThe formation of flowers is one of the main model systems to elucidate the molecular mechanisms that control developmental processes in plants. Although several studies have explored gene expression during flower development in the model plant Arabidopsis thaliana on a genome-wide scale, a continuous series of expression data from the earliest floral stages until maturation has been lacking. Here, we used a floral induction system to close this information gap and to generate a reference dataset for stage-specific gene expression during flower formation.ResultsUsing a floral induction system, we collected floral buds at 14 different stages from the time of initiation until maturation. Using whole-genome microarray analysis, we identified 7,405 genes that exhibit rapid expression changes during flower development. These genes comprise many known floral regulators and we found that the expression profiles for these regulators match their known expression patterns, thus validating the dataset. We analyzed groups of co-expressed genes for over-represented cellular and developmental functions through Gene Ontology analysis and found that they could be assigned specific patterns of activities, which are in agreement with the progression of flower development. Furthermore, by mapping binding sites of floral organ identity factors onto our dataset, we were able to identify gene groups that are likely predominantly under control of these transcriptional regulators. We further found that the distribution of paralogs among groups of co-expressed genes varies considerably, with genes expressed predominantly at early and intermediate stages of flower development showing the highest proportion of such genes.ConclusionsOur results highlight and describe the dynamic expression changes undergone by a large number of genes during flower development. They further provide a comprehensive reference dataset for temporal gene expression during flower formation and we demonstrate that it can be used to integrate data from other genomics approaches such as genome-wide localization studies of transcription factor binding sites.
Publikation

Quint, M.; Gray, W. M.; Auxin signaling Curr. Opin. Plant Biol. 9, 448-453, (2006) DOI: 10.1016/j.pbi.2006.07.006

Auxin regulates a host of plant developmental and physiological processes, including embryogenesis, vascular differentiation, organogenesis, tropic growth, and root and shoot architecture. Genetic and biochemical studies carried out over the past decade have revealed that much of this regulation involves the SCFTIR1/AFB-mediated proteolysis of the Aux/IAA family of transcriptional regulators. With the recent finding that the TRANSPORT INHIBITOR RESPONSE1 (TIR1)/AUXIN SIGNALING F-BOX (AFB) proteins also function as auxin receptors, a potentially complete, and surprisingly simple, signaling pathway from perception to transcriptional response is now before us. However, understanding how this seemingly simple pathway controls the myriad of specific auxin responses remains a daunting challenge, and compelling evidence exists for SCFTIR1/AFB-independent auxin signaling pathways.
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