Pavel Křeček

Bio: Pavel Křeček is an academic researcher from Academy of Sciences of the Czech Republic. The author has contributed to research in topics: PIN proteins & Auxin. The author has an hindex of 4, co-authored 4 publications receiving 962 citations. Previous affiliations of Pavel Křeček include Charles University in Prague.

Subcellular homeostasis of phytohormone auxin is mediated by the ER-localized PIN5 transporter

Abstract: The plant signalling molecule auxin provides positional information in a variety of developmental processes by means of its differential distribution (gradients) within plant tissues. Thus, cellular auxin levels often determine the developmental output of auxin signalling. Conceptually, transmembrane transport and metabolic processes regulate the steady-state levels of auxin in any given cell. In particular, PIN auxin-efflux-carrier-mediated, directional transport between cells is crucial for generating auxin gradients. Here we show that Arabidopsis thaliana PIN5, an atypical member of the PIN gene family, encodes a functional auxin transporter that is required for auxin-mediated development. PIN5 does not have a direct role in cell-to-cell transport but regulates intracellular auxin homeostasis and metabolism. PIN5 localizes, unlike other characterized plasma membrane PIN proteins, to endoplasmic reticulum (ER), presumably mediating auxin flow from the cytosol to the lumen of the ER. The ER localization of other PIN5-like transporters (including the moss PIN) indicates that the diversification of PIN protein functions in mediating auxin homeostasis at the ER, and cell-to-cell auxin transport at the plasma membrane, represent an ancient event during the evolution of land plants.

The PIN-FORMED (PIN) protein family of auxin transporters

Abstract: The PIN-FORMED (PIN) proteins are secondary transporters acting in the efflux of the plant signal molecule auxin from cells. They are asymmetrically localized within cells and their polarity determines the directionality of intercellular auxin flow. PIN genes are found exclusively in the genomes of multicellular plants and play an important role in regulating asymmetric auxin distribution in multiple developmental processes, including embryogenesis, organogenesis, tissue differentiation and tropic responses. All PIN proteins have a similar structure with amino- and carboxy-terminal hydrophobic, membrane-spanning domains separated by a central hydrophilic domain. The structure of the hydrophobic domains is well conserved. The hydrophilic domain is more divergent and it determines eight groups within the protein family. The activity of PIN proteins is regulated at multiple levels, including transcription, protein stability, subcellular localization and transport activity. Different endogenous and environmental signals can modulate PIN activity and thus modulate auxin-distribution-dependent development. A large group of PIN proteins, including the most ancient members known from mosses, localize to the endoplasmic reticulum and they regulate the subcellular compartmentalization of auxin and thus auxin metabolism. Further work is needed to establish the physiological importance of this unexpected mode of auxin homeostasis regulation. Furthermore, the evolution of PIN-based transport, PIN protein structure and more detailed biochemical characterization of the transport function are important topics for further studies.

Polar transport of the plant hormone auxin - the role of PIN-FORMED (PIN) proteins.

Abstract: The PIN-FORMED (PIN) protein family is a group of plant transmembrane proteins with a predicted function as secondary transporters. PINs have been shown to play a rate-limiting role in the catalysis of efflux of the plant growth regulator auxin from cells, and their asymmetrical cellular localization determines the direction of cell-to-cell auxin flow. There is a functional redundancy of PINs and their biochemical activity is regulated at many levels. PINs constitute a flexible network underlying the directional auxin flux (polar auxin transport) which provides cells in any part of the plant body with particular positional and temporal information. Thus, the PIN network, together with downstream auxin signalling system(s), coordinates plant development. This review summarizes recent progress in the elucidation of the role of PIN proteins in polar auxin transport at the cellular level, with emphasis on their structure and evolution and regulation of their function.

ER-localized PIN5 auxin transporter mediates subcellularhomeostasis of phytohormone auxin

Abstract: The plant signaling molecule auxin provides positional and directional information in a wide variety of developmental processes via its differential distribution (gradients) within plant tissues1. Thus cellular auxin levels often decide about the developmental output of auxin signaling. Conceptually, transmembrane transport and metabolic processes regulate the steady-state levels of auxin in any given cell2. In particular, PIN auxin efflux carrier-mediated, directional auxin transport between cells is crucial for generating intercellular auxin distribution3. Here we show that Arabidopsis thaliana PIN5, - an atypical member of the PIN gene family encodes a functional auxin transporter that is required for auxin-mediated development but does not play a direct role in cell-to-cell transport. Instead, PIN5 is an important factor in controlling intracellular auxin homeostasis and metabolism. PIN5 localizes, unlike other characterized plasma membrane PIN proteins, to endoplasmatic reticulum (ER) presumably mediating auxin flow from the cytosol to the lumen of ER. The ER localization of other PIN5-like transporters including the moss PIN suggests that the diversification of PIN protein functions in mediating auxin homeostasis and cell-to-cell auxin transport represents an ancient event during the evolution of land plants. Sequence manipulation revealed that PIN functional diversification could have been realized by a small sequence modification in conserved residues leading to a change in subcellular protein sorting. Our data identified an additional mode of regulating homeostasis of a plant hormone by its subcellular compartmentalization and provide insights into evolution of mechanisms controlling auxin homeostasis and transport.

Auxin transport routes in plant development.

Abstract: The differential distribution of the plant signaling molecule auxin is required for many aspects of plant development. Local auxin maxima and gradients arise as a result of local auxin metabolism and, predominantly, from directional cell-to-cell transport. In this primer, we discuss how the coordinated activity of several auxin influx and efflux systems, which transport auxin across the plasma membrane, mediates directional auxin flow. This activity crucially contributes to the correct setting of developmental cues in embryogenesis, organogenesis, vascular tissue formation and directional growth in response to environmental stimuli.

Mechanism of Auxin-Regulated Gene Expression in Plants

Abstract: Plant hormones control most aspects of the plant life cycle by regulating genome expression. Expression of auxin-responsive genes involves interactions among auxin-responsive DNA sequence elements, transcription factors and trans-acting transcriptional repressors. Transcriptional output from these auxin signaling complexes is regulated by proteasome-mediated degradation that is triggered by interaction with auxin receptor-E3 ubiquitin ligases such SCF TIR1 . Auxin signaling components are conserved throughout land plant evolution and have proliferated and specialized to control specific developmental processes.

PIN-Dependent Auxin Transport: Action, Regulation, and Evolution

Abstract: Auxin participates in a multitude of developmental processes, as well as responses to environmental cues. Compared with other plant hormones, auxin exhibits a unique property, as it undergoes directional, cell-to-cell transport facilitated by plasma membrane-localized transport proteins. Among them, a prominent role has been ascribed to the PIN family of auxin efflux facilitators. PIN proteins direct polar auxin transport on account of their asymmetric subcellular localizations. In this review, we provide an overview of the multiple developmental roles of PIN proteins, including the atypical endoplasmic reticulum-localized members of the family, and look at the family from an evolutionary perspective. Next, we cover the cell biological and molecular aspects of PIN function, in particular the establishment of their polar subcellular localization. Hormonal and environmental inputs into the regulation of PIN action are summarized as well.