Abscisic acid (ABA) receptors: light at the end of the tunnel

The plant hormone abscisic acid (ABA) plays a role in several aspects of plant growth and development. Understanding how this hormonal stimulus is sensed and transduced turned out to be one of the major tasks in the field of plant signaling. A series of recent papers proposed several different proteins that could receive the ABA signal and initiate the signaling cascade. The winner appears to be PYR/PYL/RCAR (PYrabactin Resistance/PYrabactin Resistance-Like/Regulatory Component of Abscisic acid Receptor) proteins, as crystal structures were recently published. The crystal structures support the idea that upon ABA binding to a PYR/PYL/RCAR protein, the activity of a phosphatase 2C, with known repressive activity on ABA signaling, is inhibited

Hormonal networks involved in apical hook development in darkness and their response to light

In darkness, the dicot seedlings produce an apical hook as result of differential cell division and extension at opposite sides of the hypocotyl. This hook protects the apical meristem from mechanical damage during seedling emergence from the soil. In darkness, gibberellins act via the DELLA-PIF (PHYTOCHROME INTERACTING FACTORs) pathway, and ethylene acts via the EIN3/EIL1 (ETHYLENE INSENSITIE 3/EIN3 like 1)-HLS1 (HOOKLESS 1) pathway to control the asymmetric accumulation of auxin required for apical hook formation and maintenance. These core pathways form a network with multiple points of connection. Light perception by phytochromes and cryptochromes reduces the activity of PIFs and CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) --both required for hook formation in darkness--, lowers the levels of gibberellins, and triggers hook opening as a component of the switch between heterotrophic and photoautotrophic development. Apical hook opening is thus a suitable model to study the convergence of endogenous and exogenous signals on the control of cell division and cell growth.Fil: Mazzella, Maria Agustina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular; ArgentinaFil: Casal, Jorge Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquimicas de Buenos Aires; ArgentinaFil: Muschietti, Jorge Prometeo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; ArgentinaFil: Fox, Ana Romina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular; Argentin

The pollen receptor kinase LePRK2 mediates growth-promoting signals and positively regulates pollen germination and tube growth

In flowering plants, the process of pollen germination and tube growth is required for successful fertilization. A pollen receptor kinase from tomato (Solanum lycopersicum), LePRK2, has been implicated in signaling during pollen germination and tube growth as well as in mediating pollen (tube)-pistil communication. Here we show that reduced expression of LePRK2 affects four aspects of pollen germination and tube growth. First, the percentage of pollen that germinates is reduced, and the time window for competence to germinate is also shorter. Second, the pollen tube growth rate is reduced both in vitro and in the pistil. Third, tip-localized superoxide production by pollen tubes cannot be increased by exogenous calcium ions. Fourth, pollen tubes have defects in responses to style extract component (STIL), an extracellular growth-promoting signal from the pistil. Pollen tubes transiently overexpressing LePRK2-fluorescent protein fusions had slightly wider tips, whereas pollen tubes coexpressing LePRK2 and its cytoplasmic partner protein KPP (a Rop-GEF) had much wider tips. Together these results show that LePRK2 positively regulates pollen germination and tube growth and is involved in transducing responses to extracellular growth-promoting signals.Fil: Zhang, Dong. Chinese Academy of Sciences; República de ChinaFil: Wengier, Diego Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Fisiología, Biología Molecular y Celular. Laboratorio de Fisiología y Biología Molecular; Argentina. University of California at Berkeley; Estados UnidosFil: Shuai, Bin. University of California at Berkeley; Estados UnidosFil: Gui, Cai Ping. Chinese Academy of Sciences; República de ChinaFil: Muschietti, Jorge Prometeo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Fisiología, Biología Molecular y Celular. Laboratorio de Fisiología y Biología Molecular; ArgentinaFil: McCormick, Sheila. University of California at Berkeley; Estados UnidosFil: Tang, Wei Hua. Chinese Academy of Sciences; República de China. University of California at Berkeley; Estados Unido

Pollen aquaporins: The solute factor

In the recent years, the biophysical properties and presumed physiological role of aquaporins (AQPs) have been expanded to specialized cells where water and solute exchange are crucial traits. Complex but unique processes such as stomatal movement or pollen hydration and germination have been addressed not only by identifying the specific AQP involved but also by studying how these proteins integrate and coordinate cellular activities and functions. In this review, we referred specifically to pollen-specific AQPs and analyzed what has been assumed in terms of transport properties and what has been found in terms of their physiological role. Unlike that in many other cells, the AQP machinery in mature pollen lacks plasma membrane intrinsic proteins, which are extensively studied for their high water capacity exchange. Instead, a variety of TIPs and NIPs are expressed in pollen. These findings have altered the initial understanding of AQPs and water exchange to consider specific and diverse solutes that might be critical to sustaining pollen’s success. The spatial and temporal distribution of the pollen AQPs also reflects a regulatory mechanism that allowing a properly adjusting water and solute exchange.Fil: Pérez, Juliana Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; ArgentinaFil: Soto, Gabriela Cynthia. Instituto Nacional de Tecnologia Agropecuaria. Centro de Investigacion En Ciencias Veterinarias y Agronomicas. Instituto de Agrobiotecnologia y Biologia Molecular. Grupo Vinculado Instituto de Genetica "ewald A. Favret" Al Iabimo | Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Pque. Centenario. Instituto de Agrobiotecnologia y Biologia Molecular. Grupo Vinculado Instituto de Genetica "ewald A. Favret" Al Iabimo.; ArgentinaFil: Muschietti, Jorge Prometeo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; ArgentinaFil: Amodeo, Gabriela. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Biodiversidad y Biología Experimental y Aplicada. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Biodiversidad y Biología Experimental y Aplicada; Argentin

STIL, a peculiar molecule from styles, specifically dephosphorylates the pollen receptor kinase LePRK2 and stimulates pollen tube growth in vitro

<p>Abstract</p> <p>Background</p> <p>LePRK1 and LePRK2 are two pollen receptor kinases localized to the plasma membrane, where they are present in a high molecular weight complex (LePRK complex). LePRK2 is phosphorylated in mature and germinated pollen, but is dephosphorylated when pollen membranes are incubated with tomato or tobacco style extracts.</p> <p>Results</p> <p>Here we show that LePRK2 dephosphorylation is mediated by a heat-, acid-, base-, DTT- and protease-resistant component from tobacco styles. Using LePRK2 phosphorylation as a tracking assay for purification, style exudates were subjected to chloroform extraction, anionic exchange, and C18 reverse-phase chromatography columns. We finally obtained a single ~3,550 Da compound (as determined by UV-MALDI-TOF MS) that we named STIL (for <b>St</b>yle <b>I</b>nteractor for <b>L</b>ePRKs). STIL increased pollen tube lengths of <it>in vitro </it>germinated pollen in a dose-dependent manner.</p> <p>Conclusion</p> <p>We propose that the LePRK complex perceives STIL, resulting in LePRK2 dephosphorylation and an increase in pollen tube growth.</p

Arabidopsis pollen extensins LRX are required for cell wall integrity during pollen tube growth

Proper cell wall assembly is crucial during pollen tube growth. Leucine-rich repeat extensins (LRXs) are extracellular glycoproteins which belong to the hydroxyproline-rich glycoprotein (HRGP) family. They contain a conserved N-terminal leucine-rich repeat (LRR) domain and a highly variable C-terminal extensin domain. Here, we characterized four LRX proteins (LRX8 through LRX11) from pollen of Arabidopsis thaliana. To investigate the role of LRX8-LRX11 in pollen germination and pollen tube growth, multiple T-DNA lrx mutants were obtained. The lrx mutants display abnormal pollen tubes with an irregular deposition of callose and pectin. They also show serious alterations in pollen germination and segregation ratio. Our results suggest that LRXs are involved in ensuring proper cell wall assembly during pollen tube growth.Fil: Sede, Ana Rocío. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; ArgentinaFil: Borassi, Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Fisiología, Biología Molecular y Neurociencias. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Fisiología, Biología Molecular y Neurociencias; ArgentinaFil: Wengier, Diego Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; ArgentinaFil: Mecchia, Martin Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Estevez, Jose Manuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Muschietti, Jorge Prometeo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; Argentin

Editorial: Molecular mechanisms of flowering plant reproduction

Plant reproduction is an intricate process important for the survival of all dominant autotrophs and critical in agriculture and stable food production as the basis of our diet. Angiosperms undergo extreme transformations during their ontogeny, leading to the reproductive transition. During this process, several steps are needed, including transforming a shoot apical or a lateral vegetative meristem into an inflorescence meristem with flowering competence. Floral meristems are formed from the latter accompanied by cell differentiation leading to gamete formation in specialized reproductive floral organs. Gamete interaction relies on successful pollination, whether that occurs via biotic or abiotic vectors. In addition, fertilization requires numerous molecular and hormonal signals in place and results in proper pollen tube growth, zygote viability, and seed formation. This Research Topic addresses some of the most outstanding discoveries on angiosperm reproduction in model species like Arabidopsis thaliana and Oryza sativa and crops like cauliflower, cassava, citrus, and sugarcane, among others. In the papers on the topic, the reader will discover highlights on extremely diverse floral promotion pathways, mechanisms of floral organ identity and morphogenesis, sporogenesis and gametogenesis, pollen presentation, pollination, and fertilization strategies.Fil: Pabón Mora, Natalia. Universidad de Antioquia; ColombiaFil: Goldman, Maria Helena S.. Universidade de Sao Paulo; BrasilFil: Smyth, David R.. Monash University; AustraliaFil: Muschietti, Jorge Prometeo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; ArgentinaFil: Costa, Maria Manuela R.. Universidade do Minho; Portuga

The MED30 subunit of mediator complex is essential for early plant development and promotes flowering in arabidopsis thaliana

Mediator is a large multiprotein complex that is required for the transcription of most, if not all, genes transcribed by RNA Polymerase II. A core set of subunits is essential to assemble a functional Mediator in vitro and, therefore, the corresponding loss-of-function mutants are expected to be lethal. The MED30 subunit is essential in animal systems, but is absent in yeast. Here, we report that MED30 is also essential for both male gametophyte and embryo development in the model plant Arabidopsis thaliana. Mutant med30 pollen grains were viable and some were able to germinate and target the ovules, although the embryos aborted shortly after fertilization, suggesting that MED30 is important for the paternal control of early embryo development. When gametophyte defects were bypassed by specific pollen complementation, loss of MED30 led to early embryo development arrest. Later in plant development, MED30 promotes flowering through multiple signaling pathways; its downregulation led to a phase change delay, downregulation of SQUAMOSA PROMOTER BINDING PROTEIN-LIKE 3 (SPL3), FLOWERING LOCUS T (FTI) and SUPPRESSOR OF OVEREXPRESSION OF CO 1 (SOC1), and upregulation of FLOWERING LOCUS C (FLC).Fil: Jaskolowski, Aime. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Iñigo, Sabrina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Arellano, Sofía Maité. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Arias, Leonardo Agustín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Biológicas. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Biológicas; ArgentinaFil: Fiol, Diego Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Biológicas. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Biológicas; ArgentinaFil: Sede, Ana Rocío. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; ArgentinaFil: Oldrá, María Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; ArgentinaFil: Lorenzi, Hernan. J. Craig Venter Institute; Estados UnidosFil: Muschietti, Jorge Prometeo. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Ingeniería Genética y Biología Molecular "Dr. Héctor N. Torres"; ArgentinaFil: Pagnussat, Gabriela Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Biológicas. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Biológicas; ArgentinaFil: Cerdan, Pablo Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Bioquímicas de Buenos Aires. Fundación Instituto Leloir. Instituto de Investigaciones Bioquímicas de Buenos Aires; Argentin

On Gauge Invariant Regularization of Fermion Currents

We compare Schwinger and complex powers methods to construct regularized fermion currents. We show that, although both of them are gauge invariant, they are not always yield the same result.Facultad de Ciencias Exacta