Expression divergence of the AGL6 MADS domain transcription factor lineage after a core eudicot duplication suggests functional diversification

Background: Because of their known role as transcriptional regulators of key plant developmental processes, the diversification of MADS-box gene function is thought to be a major driving force in the developmental evolution of plants. Yet the function of some MADS-box gene subfamilies has remained elusive thus far. One such lineage, AGL6, has now been functionally characterized in three angiosperm species, but a phylogenetic framework for comparison of AGL6 gene function is currently missing.status: publishe

Assessment of the attraction flow in a fish passage

An attraction flow can be used to increase the effectivity of a fish passage. In 2004 a fish passage with a perpendicular attraction flow was built at Oudenaarde (Belgium) on the Upper Scheldt river. The design of the passage was based on scale model tests. In order to evaluate the hydraulic effectivity of the attraction flow, field measurements and new scale model tests are done. Velocities in the attraction flow and the fish passage entrance are assessed quantitatively and data of the scale model tests (1/15) are compared with the field measurements. The measured reach of the attraction flow seems to differ from results of the original scale model tests due to design modifications of the fish passage entrance. Results of the new scale model tests compare well with the data from the field measurements. Based on the results, a re-examination of the basic design rules for the attraction flow and fish pass entrances seems imperativ

Tapping into the maize root microbiome to identify bacteria that promote growth under chilling conditions

Background When maize (Zea mays L.) is grown in the Northern hemisphere, its development is heavily arrested by chilling temperatures, especially at the juvenile phase. As some endophytes are beneficial for plants under stress conditions, we analyzed the impact of chilling temperatures on the root microbiome and examined whether microbiome-based analysis might help to identify bacterial strains that could promote growth under these temperatures. Results We investigated how the maize root microbiome composition changed by means of 16S rRNA gene amplicon sequencing when maize was grown at chilling temperatures in comparison to ambient temperatures by repeatedly cultivating maize in field soil. We identified 12 abundant and enriched bacterial families that colonize maize roots, consisting of bacteria recruited from the soil, whereas seed-derived endophytes were lowly represented. Chilling temperatures modified the root microbiome composition only slightly, but significantly. An enrichment of several chilling-responsive families was detected, of which the Comamonadaceae and the Pseudomonadaceae were the most abundant in the root endosphere of maize grown under chilling conditions, whereas only three were strongly depleted, among which the Streptomycetaceae. Additionally, a collection of bacterial strains isolated from maize roots was established and a selection was screened for growth-promoting effects on juvenile maize grown under chilling temperatures. Two promising strains that promoted maize growth under chilling conditions were identified that belonged to the root endophytic bacterial families, from which the relative abundance remained unchanged by variations in the growth temperature. Conclusions Our analyses indicate that chilling temperatures affect the bacterial community composition within the maize root endosphere. We further identified two bacterial strains that boost maize growth under chilling conditions. Their identity revealed that analyzing the chilling-responsive families did not help for their identification. As both strains belong to root endosphere enriched families, visualizing and comparing the bacterial diversity in these communities might still help to identify new PGPR strains. Additionally, a strain does not necessarely need to belong to a high abundant family in the root endosphere to provoke a growth-promoting effect in chilling conditions

Directional auxin transport mechanisms in early diverging land plants

The emergence and radiation of multicellular land plants was driven by crucial innovations to their body plans [1]. The directional transport of the phytohormone auxin represents a key, plant-specific mechanism for polarization and patterning in complex seed plants [2, 3, 4 and 5]. Here, we show that already in the early diverging land plant lineage, as exemplified by the moss Physcomitrella patens, auxin transport by PIN transporters is operational and diversified into ER-localized and plasma membrane-localized PIN proteins. Gain-of-function and loss-of-function analyses revealed that PIN-dependent intercellular auxin transport in Physcomitrella mediates crucial developmental transitions in tip-growing filaments and waves of polarization and differentiation in leaf-like structures. Plasma membrane PIN proteins localize in a polar manner to the tips of moss filaments, revealing an unexpected relation between polarization mechanisms in moss tip-growing cells and multicellular tissues of seed plants. Our results trace the origins of polarization and auxin-mediated patterning mechanisms and highlight the crucial role of polarized auxin transport during the evolution of multicellular land plants

PIN-driven auxin transport emerged early in streptophyte evolution

PIN-FORMED (PIN) transporters mediate directional, intercellular movement of the phytohormone auxin in land plants. To elucidate the evolutionary origins of this developmentally crucial mechanism, we analysed the single PIN homologue of a simple green alga Klebsormidium flaccidum. KfPIN functions as a plasma membrane-localized auxin exporter in land plants and heterologous models. While its role in algae remains unclear, PIN-driven auxin export is probably an ancient and conserved trait within streptophytes

Cis-cinnamic acid is a novel natural auxin efflux inhibitor that promotes lateral root formation

Auxin steers numerous physiological processes in plants, making the tight control of its endogenous levels and spatiotemporal distribution a necessity. This regulation is achieved by different mechanisms, including auxin biosynthesis, metabolic conversions, degradation, and transport. Here, we introduce cis-cinnamic acid (c-CA) as a novel and unique addition to a small group of endogenous molecules affecting in planta auxin concentrations. c-CA is the photo-isomerization product of the phenylpropanoid pathway intermediate trans-CA (t-CA). When grown on c-CA-containing medium, an evolutionary diverse set of plant species were shown to exhibit phenotypes characteristic for high auxin levels, including inhibition of primary root growth, induction of root hairs, and promotion of adventitious and lateral rooting. By molecular docking and receptor binding assays, we showed that c-CA itself is neither an auxin nor an anti-auxin, and auxin profiling data revealed that c-CA does not significantly interfere with auxin biosynthesis. Single cell-based auxin accumulation assays showed that c-CA, and not t-CA, is a potent inhibitor of auxin efflux. Auxin signaling reporters detected changes in spatiotemporal distribution of the auxin response along the root of c-CA-treated plants, and long-distance auxin transport assays showed no inhibition of rootward auxin transport. Overall, these results suggest that the phenotypes of c-CA-treated plants are the consequence of a local change in auxin accumulation, induced by the inhibition of auxin efflux. This work reveals a novel mechanism how plants may regulate auxin levels and adds a novel, naturally occurring molecule to the chemical toolbox for the studies of auxin homeostasis

The 42nd Symposium Chromatographic Methods of Investigating Organic Compounds : Book of abstracts

The 42nd Symposium Chromatographic Methods of Investigating Organic Compounds : Book of abstracts. June 4-7, 2019, Szczyrk, Polan

Evolution of ancient MADS-gene functions.

Dit proefschrift bestudeert de evolutie van de functie van verschillende subfamilies binnen de MADS-box genfamilie. MADS-box genen functioneren als transcriptiefactoren en spelen een belangrijke rol in verschillende ontwikkelingsprocessen van bloeiende planten. Studies over de evolutie v an deze genfamilie hebben reeds aangetoond dat deze genfamilie gekenmerk t wordt door herhaalde en frequente genduplicatie, waarbij de transcript iefactoren na duplicatie behouden worden in het genoom. Een dergelijk pa troon van genduplicatie creëert een potentieel voor functionele diversif icatie via wijzigingen in de spatiotemporele expressie of door veranderi ngen in eiwit-eiwit interactiespecificiteit.. De eerste twee hoofdstukken bestuderen het patroon van genduplicatie en genverlies in twee verschillende MADS-box subfamilies, PISTILLATA en AGL 6. In een eerste hoofdstuk reconstrueren we de evolutie van PISTILLATA e n twee van zijn interactiepartners, TM6 and APETALA3, in de asteriden. H iervoor hebben we nieuwe B-klasse genen geïsoleerd uit basale asteriden en gecombineerd met EST-data. Onze resultaten suggereren dat zowel gedur ende de evolutie van de basale asteriden als doorheen de evolutie van de kernasteriden, oude en recente duplicaties zijn opgetreden in de PISTIL LATA-subfamilie. Bovendien correleren deze duplicaties niet met gelijkaa rdige duplicaties in de evolutie van de interactiepartners TM6 en APETAL A3. We hebben ook de evolutie na duplicatie bestudeerd voor een aantal v an deze gedupliceerde genen via RT-PCR, in situ hybridisatie en yeast-2- hybrid. Samen met informatie over andere soorten uit de groep van de ker nasteriden suggereren deze data dat, gedurende de evolutie van ast eriden, verschillende PISTILLATA duplicaties zijn opgetreden en dat deze gedupliceerde genen kunnen aangewend worden voor nieuwe functies in de bloem. In een tweede hoofdstuk wordt de evolutie van de AGL6-subfamilie doorhee n de bloemplanten beschreven. In totaal werden vier nieuwe duplicaties g eïdentificeerd; één aan de basis van de kerneudicotylen die resulteerde in een AGL6-like en een euAGL6 groep, een tweede gedurende de evolutie v an de basale angiospermen en twee extra duplicaties gedurende de evoluti e van de monocotylen. We hebben de expressiepatronen van deze genfamilie bepaald via kwantitatieve real time PCR om na te geen hoe deze subfamil e is gediversifieerd na duplicatie. Een van beide clades die ontstaan is na de duplicatie aan de basis van de kerneudicotylen (AGL6-like) komt s terk tot expressie in vegetatief weefsel, terwijl de andere clade (euAGL 6) vooral tot expressie komt in reproductieve weefsels. We suggereren da t, na duplicatie aan de basis van de kerneudicotylen, AGL6 een functie h eeft verkregen in de transitie van vegetatieve scheuten, naast de gekend e voorouderlijke functie in reproductieve structuren. In een derde hoofdstuk hebben we de evolutie en functie van een derde MA DS-box subfamile bestudeerd, TM8. Deze subfamilie heeft geen vertegenwoo rdigers in de modelplanten Arabidopsis en rijst en bovendien werd er nog geen enkele TM8-vertegenwoordiger functioneel gekarakteriseerd. In een eerste fase hebben we de reeds beschikbare TM8-vertegenwoordigers in ang iospermen geïdentificeerd en stellen als eerste een reconstructie van de evolutie van deze subfamilie voor. Deze resultaten suggereren dat genve rlies vermoedelijk is opgetreden in de evolutionaire lijn die leidt naar de monocotylen en de Brassicales. Vervolgens hebben we door middel van virus induced gene silencing de functie van TM8 gekarakteriseerd in Nico tiana benthamiana. De interactie van TM8 met SVP (SHORT VEGETATIVE PHASE ), een ander MADS-box gen dat een rol speelt in de controle van bloeitij d in Arabidopsis thaliana, speelt hierin een cruciale rol. Zo hebben we TM8 geïdentificeerd als een bloeirepressor die zijn functie vervult door een gekende promoter van bloei, FLOWERING LOCUS T (FT), te onderdrukken. De effecten op bloeijtijd zouden ook tot stand kunnen kome n via twee andere kleine RNA-molecules, miR156 en miR172. Voor beide is reeds aangetoond dat ze zowel de juveniele-adulte overgang als de bloei- inductie beïnvloeden in Arabidopsis. Onze data suggereren inderdaad dat TM8 (en vermoedelijk ook SVP) een rol spelen in de controle van de juven iele-adulte overgang in Nicotiana benthamiana. Tenslotte hebben we ook v ia virus induced gene silencing in Papaver somniferum aangetoond dat TM8 eveneens beide microRNA s reguleert, wat suggereert dat dit mechanisme geconserveerd is doorheen de evolutie.status: publishe