Albany, CA, United States
Albany, CA, United States

Time filter

Source Type

Soy J.,Autonomous University of Barcelona | Leivar P.,Autonomous University of Barcelona | Gonzalez-Schain N.,Autonomous University of Barcelona | Sentandreu M.,Autonomous University of Barcelona | And 4 more authors.
Plant Journal | Year: 2012

Arabidopsis seedlings display rhythmic growth when grown under diurnal conditions, with maximal elongation rates occurring at the end of the night under short-day photoperiods. Current evidence indicates that this behavior involves the action of the growth-promoting bHLH factors PHYTOCHROME-INTERACTING FACTOR 4 (PIF4) and PHYTOCHROME-INTERACTING FACTOR 5 (PIF5) at the end of the night, through a coincidence mechanism that combines their transcriptional regulation by the circadian clock with control of protein accumulation by light. To assess the possible role of PIF3 in this process, we have analyzed hypocotyl responses and marker gene expression in pif single- and higher-order mutants. The data show that PIF3 plays a prominent role as a promoter of seedling growth under diurnal light/dark conditions, in conjunction with PIF4 and PIF5. In addition, we provide evidence that PIF3 functions in this process through its intrinsic transcriptional regulatory activity, at least in part by directly targeting growth-related genes, and independently of its ability to regulate phytochrome B (phyB) levels. Furthermore, in sharp contrast to PIF4 and PIF5, our data show that the PIF3 gene is not subject to transcriptional regulation by the clock, but that PIF3 protein abundance oscillates under diurnal conditions as a result of a progressive decline in PIF3 protein degradation mediated by photoactivated phyB, and consequent accumulation of the bHLH factor during the dark period. Collectively, the data suggest that phyB-mediated, post-translational regulation allows PIF3 accumulation to peak just before dawn, at which time it accelerates hypocotyl growth, together with PIF4 and PIF5, by directly regulating the induction of growth-related genes. © 2012 The Authors.


Sentandreu M.,Autonomous University of Barcelona | Martin G.,Autonomous University of Barcelona | Gonzalez-Schain N.,Autonomous University of Barcelona | Leivar P.,Autonomous University of Barcelona | And 6 more authors.
Plant Cell | Year: 2011

The phytochrome (phy)-interacting basic helix-loop-helix transcription factors (PIFs) constitutively sustain the etiolated state of dark-germinated seedlings by actively repressing deetiolation in darkness. This action is rapidly reversed upon light exposure by phy-induced proteolytic degradation of the PIFs. Here, we combined a microarray-based approach with a functional profiling strategy and identified four PIF3-regulated genes misexpressed in the dark (MIDAs) that are novel regulators of seedling deetiolation. We provide evidence that each one of these four MIDA genes regulates a specific facet of etiolation (hook maintenance, cotyledon appression, or hypocotyl elongation), indicating that there is branching in the signaling that PIF3 relays. Furthermore, combining inferred MIDA gene function from mutant analyses with their expression profiles in response to light-induced degradation of PIF3 provides evidence consistent with a model where the action of the PIF3/MIDA regulatory network enables an initial fast response to the light and subsequently prevents an overresponse to the initial light trigger, thus optimizing the seedling deetiolation process. Collectively, the data suggest that at least part of the phy/ PIF system acts through these four MIDAs to initiate and optimize seedling deetiolation, and that this mechanism might allow the implementation of spatial (i.e., organ-specific) and temporal responses during the photomorphogenic program. © 2011 American Society of Plant Biologists. All rights reserved.


Burko Y.,Hebrew University | Geva Y.,Hebrew University | Refael-Cohen A.,Hebrew University | Shleizer-Burko S.,Hebrew University | And 6 more authors.
Plant and Cell Physiology | Year: 2011

Plant architecture is a predictable but flexible trait. The timing and position of organ initiation from the shoot apical meristem (SAM) contribute to the final plant form. While much progress has been made recently in understanding how the site of leaf initiation is determined, the mechanism underlying the temporal interval between leaf primordia is still largely unknown. The Arabidopsis ZRIZI (ZRZ) gene belongs to a large gene family encoding multidrug and toxic compound extrusion (MATE) transporters. Unique among plant MATE transporters identified so far, ZRZ is localized to the membrane of a small organelle, possibly the mitochondria. Plants overexpressing ZRZ in initiating leaves are short, produce leaves much faster than wild-type plants and show enhanced growth of axillary buds. These results suggest that ZRZ is involved in communicating a leaf-borne signal that determines the rate of organ initiation. © 2011 The Author.


Moon H.S.,University of Tennessee at Knoxville | Abercrombie L.L.,University of Tennessee at Knoxville | Eda S.,University of Tennessee at Knoxville | Blanvillain R.,Plant Gene Expression Center | And 5 more authors.
Plant Molecular Biology | Year: 2011

Transgene escape, a major environmental and regulatory concern in transgenic crop cultivation, could be alleviated by removing transgenes from pollen, the most frequent vector for transgene flow. A transgene excision vector containing a codon optimized serine resolvase CinH recombinase (CinH) and its recognition sites RS2 were constructed and transformed into tobacco (Nicotiana tabacum cv. Xanthi). CinH recombinase recognized 119 bp of nucleic acid sequences, RS2, in pollen and excised the transgene flanked by the RS2 sites. In this system, the pollen-specific LAT52 promoter from tomato was employed to control the expression of CinH recombinase. Loss of expression of a green fluorescent protein (GFP) gene under the control of the LAT59 promoter from tomato was used as an indicator of transgene excision. Efficiency of transgene excision from pollen was determined by flow cytometry (FCM)-based pollen screening. While a transgenic event in the absence of CinH recombinase contained about 70% of GFP-synthesizing pollen, three single-copy transgene events contained less than 1% of GFP-synthesizing pollen based on 30,000 pollen grains analyzed per event. This suggests that CinH-RS2 recombination system could be effectively utilized for transgene biocontainment. © 2011 Springer Science+Business Media B.V. (outside the USA).


Pfeiffer A.,University of California at Berkeley | Pfeiffer A.,Plant Gene Expression Center | Shi H.,University of California at Berkeley | Shi H.,Plant Gene Expression Center | And 6 more authors.
Molecular Plant | Year: 2014

A subfamily of four Phytochrome (phy)-Interacting bHLH transcription Factors (PIFs) collectively promote skotomorphogenic development in dark-grown seedlings. This activity is reversed upon exposure to light, by photoactivated phy molecules that induce degradation of the PIFs, thereby triggering the transcriptional changes that drive a transition to photomorphogenesis. The PIFs function both redundantly and partially differentially at the morphogenic level in this process. To identify the direct targets of PIF transcriptional regulation genome-wide, we analyzed the DNA-binding sites for all four PIFs by ChIP-seq analysis, and defined the genes transcriptionally regulated by each PIF, using RNA-seq analysis of pif mutants. Despite the absence of detectable differences in DNA-binding-motif recognition between the PIFs, the data show a spectrum of regulatory patterns, ranging from single PIF dominance to equal contributions by all four. Similarly, a broad array of promoter architectures was found, ranging from single PIF-binding sites, containing single sequence motifs, through multiple PIF-binding sites, each containing one or more motifs, with each site occupied preferentially by one to multiple PIFs. Quantitative analysis of the promoter occupancy and expression level induced by each PIF revealed an intriguing pattern. Although there is no robust correlation broadly across the target-gene population, examination of individual genes that are shared targets of multiple PIFs shows a gradation in correlation from strongly positive, through uncorrelated, to negative. This finding suggests a dual-layered mechanism of transcriptional regulation, comprising both a continuum of binding-site occupancy by each PIF and a superimposed layer of local regulation that acts differentially on each PIF, to modulate its intrinsic transcriptional activation capacity at each site, in a quantitative pattern that varies between the individual PIFs from gene to gene. These findings provide a framework for probing the mechanisms by which transcription factors with overlapping direct-target genes integrate and selectively transduce signals to their target networks. © 2014 The Authors. All rights reserved.


Chuck G.S.,Plant Gene Expression Center | Brown P.J.,Urbana University | Meeley R.,DuPont Pioneer | Hake S.,Plant Gene Expression Center
Proceedings of the National Academy of Sciences of the United States of America | Year: 2014

The separation of male and female flowers in maize provides the potential for independent regulation of traits that affect crop productivity. For example, tassel branch number controls pollen abundance and length of shedding time, whereas ear row number directly affects kernel yield. Mutations in duplicate SBP-box transcription factor genes unbranched2 (ub2) and ub3 affect both of these yield traits. Double mutants display a decrease in tassel branch number and an increase in ear row number, both of which are enhanced by loss of a related gene called tasselsheath4 (tsh4). Furthermore, triple mutants have more tillers and leaves - phenotypes seen in Corngrass1 mutants that result from widespread repression of SBP-box genes. Immunolocalization of UB2 and UB3 proteins revealed accumulation throughout the meristem but absence from the central domain of the meristem where cells regenerate. Thus, ub2, ub3, and tsh4 function as redundant factors that limit the rate of cell differentiation to the lateral domains of meristems. When these genes are mutated, cells are allocated to lateral primordia at a higher rate, causing a net loss of cells from the central domain and premature termination of the inflorescence. The ub3 locus is tightly linked to quantitative trait loci (QTL) for ear row number and tassel branch number in both the nested association mapping (NAM) and intermated B73 by Mo17 (IBM) populations of maize recombinant inbreds, indicating that this gene may be agronomically important. Analysis of ear and tassel QTL across biparental families suggests that multiple mutations in ub3 independently regulate male and female inflorescence development. © 2014, National Academy of Sciences. All rights reserved.


Leivar P.,University of California at Berkeley | Leivar P.,Plant Gene Expression Center | Leivar P.,Center for Research in Agricultural Genomics | Quail P.H.,University of California at Berkeley | Quail P.H.,Plant Gene Expression Center
Trends in Plant Science | Year: 2011

A small subset of basic helix-loop-helix transcription factors called PIFs (phytochrome-interacting factors) act to repress seed germination, promote seedling skotomorphogenesis and promote shade-avoidance through regulated expression of over a thousand genes. Light-activated phytochrome molecules directly reverse these activities by inducing rapid degradation of the PIF proteins. Here, we review recent advances in dissecting this signaling pathway and examine emerging evidence that indicates that other pathways also converge to regulate PIF activity, including the gibberellin pathway, the circadian clock and high temperature. Thus PIFs have broader roles than previously appreciated, functioning as a cellular signaling hub that integrates multiple signals to orchestrate regulation of the transcriptional network that drives multiple facets of downstream morphogenesis. The relative contributions of the individual PIFs to this spectrum of regulatory functions ranges from quantitatively redundant to qualitatively distinct. © 2010 Elsevier Ltd.


Schreiber K.J.,University of California at Berkeley | Baudin M.,University of California at Berkeley | Hassan J.A.,University of California at Berkeley | Lewis J.D.,University of California at Berkeley | Lewis J.D.,Plant Gene Expression Center
Seminars in Cell and Developmental Biology | Year: 2016

Bacterial pathogens inject type III secreted effector (T3SE) proteins into their hosts where they display dual roles depending on the host genotype. T3SEs promote bacterial virulence in susceptible hosts, and elicit immunity in resistant hosts. T3SEs are typically recognized when they modify a host target that is associated with a NOD-like receptor protein. We focus on the molecular mechanisms of T3SE recognition in plants. Plants guard multiple nodes of the immune signaling pathway, from recognition at the cell surface by receptor-like kinases to nuclear signaling. Some nodes are bacterial virulence targets, while other nodes are decoys that resemble true virulence targets. © 2016


Leivar P.,University of California at Berkeley | Leivar P.,Plant Gene Expression Center | Leivar P.,Center for Research in Agricultural Genomics IRTA UAB UB | Monte E.,Center for Research in Agricultural Genomics IRTA UAB UB | And 4 more authors.
Molecular Plant | Year: 2012

The reversibly red (R)/far-red (FR)-light-responsive phytochrome (phy) photosensory system initiates both the deetiolation process in dark-germinated seedlings upon first exposure to light, and the shade-avoidance process in fully deetiolated seedlings upon exposure to vegetational shade. The intracellular signaling pathway from the light-activated photoreceptor conformer (Pfr) to the transcriptional network that drives these responses involves direct, physical interaction of Pfr with a small subfamily of bHLH transcription factors, termed Phy-Interacting Factors (PIFs), which induces rapid PIF proteolytic degradation. In addition, there is evidence of further complexity in light-grown seedlings, whereby phyB-PIF interaction reciprocally induces phyB degradation, in a mutually-negative, feedback-loop configuration. Here, to assess the relative contributions of these antagonistic activities to the net phenotypic readout in light-grown seedlings, we have examined the magnitude of the light- and simulated-shade-induced responses of a pentuple phyBpif1pif3pif4pif5 (phyBpifq) mutant and various multiple pif-mutant combinations. The data (1) reaffirm that phyB is the predominant, if not exclusive, photoreceptor imposing the inhibition of hypocotyl elongation in deetiolating seedlings in response to prolonged continuous R irradiation and (2) show that the PIF quartet (PIF1, PIF3, PIF4, and PIF5) retain and exert a dual capacity to modulate hypocotyl elongation under these conditions, by concomitantly promoting cell elongation through intrinsic transcriptional-regulatory activity, and reducing phyB-inhibitory capacity through feedback-loop-induced phyB degradation. In shade-exposed seedlings, immunoblot analysis shows that the shade-imposed reduction in Pfr levels induces increases in the abundance of PIF3, and mutant analysis indicates that PIF3 acts, in conjunction with PIF4 and PIF5, to promote the known shade-induced acceleration of hypocotyl elongation. Conversely, although the quadruple pifq mutant displays clearly reduced hypocotyl elongation compared to wild-type in response to prolonged shade, immunoblot analysis detects no elevation in phyB levels in the mutant seedlings compared to the wild-type during the majority of the shade-induced growth period, and phyB levels are not robustly correlated with the growth phenotype across the pif-mutant combinations compared. These results suggest that PIF feedback modulation of phyB abundance does not play a dominant role in modulating the magnitude of the PIF-promoted, shade-responsive phenotype under these conditions. In seedlings grown under diurnal light-dark cycles, the data show that FR-pulse-induced removal of Pfr at the beginning of the dark period (End-of-Day-FR (EOD-FR) treatment) results in longer hypocotyls relative to no EOD-FR treatment and that this effect is attenuated in the pif-mutant combinations tested. This result similarly indicates that the PIF quartet members are capable of intrinsically promoting hypocotyl cell elongation in light-grown plants, independently of the effects of PIF feedback modulation of photoactivated-phyB abundance. © 2012 The Author.


Franklin K.A.,University of Leicester | Quail P.H.,University of California at Berkeley | Quail P.H.,Plant Gene Expression Center
Journal of Experimental Botany | Year: 2010

Light signals are fundamental to the growth and development of plants. Red and far-red light are sensed using the phytochrome family of plant photoreceptors. Individual phytochromes display both unique and overlapping roles throughout the life cycle of plants, regulating a range of developmental processes from seed germination to the timing of reproductive development. The evolution of multiple phytochrome photoreceptors has enhanced plant sensitivity to fluctuating light environments, diversifying phytochrome function, and facilitating conditional cross-talk with other signalling systems. The isolation of null mutants, deficient in all individual phytochromes, has greatly advanced understanding of phytochrome functions in the model species, Arabidopsis thaliana. The creation of mutants null for multiple phytochrome combinations has enabled the dissection of redundant interactions between family members, revealing novel regulatory roles for this important photoreceptor family. In this review, current knowledge of phytochrome functions in the light-regulated development of Arabidopsis is summarised.

Loading Plant Gene Expression Center collaborators
Loading Plant Gene Expression Center collaborators