TY - JOUR AB - Strigolactones, first discovered as germination stimulants for parasitic weeds [1], are carotenoid-derived phytohormones that play major roles in inhibiting lateral bud outgrowth and promoting plant-mycorrhizal symbiosis [2-4]. Furthermore, strigolactones are involved in the regulation of lateral and adventitious root development, root cell division [5, 6], secondary growth [7], and leaf senescence [8]. Recently, we discovered the strigolactone transporter Petunia axillaris PLEIOTROPIC DRUG RESISTANCE 1 (PaPDR1), which is required for efficient mycorrhizal colonization and inhibition of lateral bud outgrowth [9]. However, how strigolactones are transported through the plant remained unknown. Here we show that PaPDR1 exhibits a cell-type-specific asymmetric localization in different root tissues. In root tips, PaPDR1 is co-expressed with the strigolactone biosynthetic gene DAD1 (CCD8), and it is localized at the apical membrane of root hypodermal cells, presumably mediating the shootward transport of strigolactone. Above the root tip, in the hypodermal passage cells that form gates for the entry of mycorrhizal fungi, PaPDR1 is present in the outer-lateral membrane, compatible with its postulated function as strigolactone exporter from root to soil. Transport studies are in line with our localization studies since (1) a papdr1 mutant displays impaired transport of strigolactones out of the root tip to the shoot as well as into the rhizosphere and (2) DAD1 expression and PIN1/PIN2 levels change in plants deregulated for PDR1 expression, suggestive of variations in endogenous strigolactone contents. In conclusion, our results indicate that the polar localizations of PaPDR1 mediate directional shootward strigolactone transport as well as localized exudation into the soil. AU - Sasse, Joëlle AU - Simon, Sibu AU - Gübeli, Christian AU - Liu, Guowei AU - Cheng, Xi AU - Friml, Jirí AU - Bouwmeester, Harro AU - Martinoia, Enrico AU - Borghi, Lorenzo ID - 1536 IS - 5 JF - Current Biology TI - Asymmetric localizations of the ABC transporter PaPDR1 trace paths of directional strigolactone transport VL - 25 ER - TY - JOUR AB - A plethora of diverse programmed cell death (PCD) processes has been described in living organisms. In animals and plants, different forms of PCD play crucial roles in development, immunity, and responses to the environment. While the molecular control of some animal PCD forms such as apoptosis is known in great detail, we still know comparatively little about the regulation of the diverse types of plant PCD. In part, this deficiency in molecular understanding is caused by the lack of reliable reporters to detect PCD processes. Here, we addressed this issue by using a combination of bioinformatics approaches to identify commonly regulated genes during diverse plant PCD processes in Arabidopsis (Arabidopsis thaliana). Our results indicate that the transcriptional signatures of developmentally controlled cell death are largely distinct from the ones associated with environmentally induced cell death. Moreover, different cases of developmental PCD share a set of cell death-associated genes. Most of these genes are evolutionary conserved within the green plant lineage, arguing for an evolutionary conserved core machinery of developmental PCD. Based on this information, we established an array of specific promoter-reporter lines for developmental PCD in Arabidopsis. These PCD indicators represent a powerful resource that can be used in addition to established morphological and biochemical methods to detect and analyze PCD processes in vivo and in planta. AU - Olvera Carrillo, Yadira AU - Van Bel, Michiel AU - Van Hautegem, Tom AU - Fendrych, Matyas AU - Huysmans, Marlies AU - Šimášková, Mária AU - Van Durme, Matthias AU - Buscaill, Pierre AU - Rivas, Susana AU - Coll, Núria AU - Coppens, Frederik AU - Maere, Steven AU - Nowack, Moritz ID - 1543 IS - 4 JF - Plant Physiology TI - A conserved core of programmed cell death indicator genes discriminates developmentally and environmentally induced programmed cell death in plants VL - 169 ER - TY - JOUR AB - The elongator complex subunit 2 (ELP2) protein, one subunit of an evolutionarily conserved histone acetyltransferase complex, has been shown to participate in leaf patterning, plant immune and abiotic stress responses in Arabidopsis thaliana. Here, its role in root development was explored. Compared to the wild type, the elp2 mutant exhibited an accelerated differentiation of its root stem cells and cell division was more active in its quiescent centre (QC). The key transcription factors responsible for maintaining root stem cell and QC identity, such as AP2 transcription factors PLT1 (PLETHORA1) and PLT2 (PLETHORA2), GRAS transcription factors such as SCR (SCARECROW) and SHR (SHORT ROOT) and WUSCHEL-RELATED HOMEOBOX5 transcription factor WOX5, were all strongly down-regulated in the mutant. On the other hand, expression of the G2/M transition activator CYCB1 was substantially induced in elp2. The auxin efflux transporters PIN1 and PIN2 showed decreased protein levels and PIN1 also displayed mild polarity alterations in elp2, which resulted in a reduced auxin content in the root tip. Either the acetylation or methylation level of each of these genes differed between the mutant and the wild type, suggesting that the ELP2 regulation of root development involves the epigenetic modification of a range of transcription factors and other developmental regulators. AU - Jia, Yuebin AU - Tian, Huiyu AU - Li, Hongjiang AU - Yu, Qianqian AU - Wang, Lei AU - Friml, Jirí AU - Ding, Zhaojun ID - 1556 IS - 15 JF - Journal of Experimental Botany TI - The Arabidopsis thaliana elongator complex subunit 2 epigenetically affects root development VL - 66 ER - TY - JOUR AB - CyclophilinAis a conserved peptidyl-prolyl cis-trans isomerase (PPIase) best known as the cellular receptor of the immunosuppressant cyclosporine A. Despite significant effort, evidence of developmental functions of cyclophilin A in non-plant systems has remained obscure. Mutations in a tomato (Solanum lycopersicum) cyclophilin A ortholog, DIAGEOTROPICA (DGT), have been shown to abolish the organogenesis of lateral roots; however, a mechanistic explanation of the phenotype is lacking. Here, we show that the dgt mutant lacks auxin maxima relevant to priming and specification of lateral root founder cells. DGT is expressed in shoot and root, and localizes to both the nucleus and cytoplasm during lateral root organogenesis. Mutation of ENTIRE/ IAA9, a member of the auxin-responsive Aux/IAA protein family of transcriptional repressors, partially restores the inability of dgt to initiate lateral root primordia but not the primordia outgrowth. By comparison, grafting of a wild-type scion restores the process of lateral root formation, consistent with participation of a mobile signal. Antibodies do not detect movement of the DGT protein into the dgt rootstock; however, experiments with radiolabeled auxin and an auxin-specific microelectrode demonstrate abnormal auxin fluxes. Functional studies of DGT in heterologous yeast and tobacco-leaf auxin-transport systems demonstrate that DGT negatively regulates PIN-FORMED (PIN) auxin efflux transporters by affecting their plasma membrane localization. Studies in tomato support complex effects of the dgt mutation on PIN expression level, expression domain and plasma membrane localization. Our data demonstrate that DGT regulates auxin transport in lateral root formation. AU - Ivanchenko, Maria AU - Zhu, Jinsheng AU - Wang, Bangjun AU - Medvecka, Eva AU - Du, Yunlong AU - Azzarello, Elisa AU - Mancuso, Stefano AU - Megraw, Molly AU - Filichkin, Sergei AU - Dubrovsky, Joseph AU - Friml, Jirí AU - Geisler, Markus ID - 1558 IS - 4 JF - Development TI - The cyclophilin a DIAGEOTROPICA gene affects auxin transport in both root and shoot to control lateral root formation VL - 142 ER - TY - JOUR AB - The visualization of hormonal signaling input and output is key to understanding how multicellular development is regulated. The plant signaling molecule auxin triggers many growth and developmental responses, but current tools lack the sensitivity or precision to visualize these. We developed a set of fluorescent reporters that allow sensitive and semiquantitative readout of auxin responses at cellular resolution in Arabidopsis thaliana. These generic tools are suitable for any transformable plant species. AU - Liao, Cheyang AU - Smet, Wouter AU - Brunoud, Géraldine AU - Yoshida, Saiko AU - Vernoux, Teva AU - Weijers, Dolf ID - 1554 IS - 3 JF - Nature Methods TI - Reporters for sensitive and quantitative measurement of auxin response VL - 12 ER -