Nitric oxide and salicylic acid signaling in plant defense

Salicylic acid (SA) plays a critical signaling role in the activation of plant defense responses after pathogen attack. We have identified several potential components of the SA signaling pathway, including (i) the H2O2-scavenging enzymes catalase and ascorbate peroxidase, (ii) a high affinity SA-binding protein (SABP2), (iii) a SA-inducible protein kinase (SIPK), (iv) NPR1, an ankyrin repeat-containing protein that exhibits limited homology to IκBα and is required for SA signaling, and (v) members of the TGA/OBF family of bZIP transcription factors. These bZIP factors physically interact with NPR1 and bind the SA-responsive element in promoters of several defense genes, such as the pathogenesis-related 1 gene (PR-1). Recent studies have demonstrated that nitric oxide (NO) is another signal that activates defense responses after pathogen attack. NO has been shown to play a critical role in the activation of innate immune and inflammatory responses in animals. Increases in NO synthase (NOS)-like activity occurred in resistant but not susceptible tobacco after infection with tobacco mosaic virus. Here we demonstrate that this increase in activity participates in PR-1 gene induction. Two signaling molecules, cGMP and cyclic ADP ribose (cADPR), which function downstream of NO in animals, also appear to mediate plant defense gene activation (e.g., PR-1). Additionally, NO may activate PR-1 expression via an NO-dependent, cADPR-independent pathway. Several targets of NO in animals, including guanylate cyclase, aconitase, and mitogen-activated protein kinases (e.g., SIPK), are also modulated by NO in plants. Thus, at least portions of NO signaling pathways appear to be shared between plants and animals.

Myosin Vb Is Associated with Plasma Membrane Recycling Systems

Myosin Va is associated with discrete vesicle populations in a number of cell types, but little is known of the function of myosin Vb. Yeast two-hybrid screening of a rabbit parietal cell cDNA library with dominant active Rab11a (Rab11aS20V) identified myosin Vb as an interacting protein for Rab11a, a marker for plasma membrane recycling systems. The isolated clone, corresponding to the carboxyl terminal 60 kDa of the myosin Vb tail, interacted with all members of the Rab11 family (Rab11a, Rab11b, and Rab25). GFP-myosin Vb and endogenous myosin Vb immunoreactivity codistributed with Rab11a in HeLa and Madin-Darby canine kidney (MDCK) cells. As with Rab11a in MDCK cells, the myosin Vb immunoreactivity was dispersed with nocodazole treatment and relocated to the apical corners of cells with taxol treatment. A green fluorescent protein (GFP)-myosin Vb tail chimera overexpressed in HeLa cells retarded transferrin recycling and caused accumulation of transferrin and the transferrin receptor in pericentrosomal vesicles. Expression of the myosin Vb tail chimera in polarized MDCK cells stably expressing the polymeric IgA receptor caused accumulation of basolaterally endocytosed polymeric IgA and the polymeric IgA receptor in the pericentrosomal region. The myosin Vb tail had no effects on transferrin trafficking in polarized MDCK cells. The GFP-myosin Va tail did not colocalize with Rab11a and had no effects on recycling system vesicle distribution in either HeLa or MDCK cells. The results indicate myosin Vb is associated with the plasma membrane recycling system in nonpolarized cells and the apical recycling system in polarized cells. The dominant negative effects of the myosin Vb tail chimera indicate that this unconventional myosin is required for transit out of plasma membrane recycling systems.

Importancia de la caracterización de la masa de raíces en la simulación de ecosistemas forestales

Los análisis de sensibilidad son una herramienta importante para comprender el funcionamiento de los modelos ecológicos, así como para identificar los parámetros más importantes en su funcionamiento. Además, los análisis de sensibilidad pueden utilizarse para diseñar de forma más efectiva planes de muestreo de campo dirigidos a calibrar los modelos ecológicos. En los estudios de ecosistemas forestales, el análisis cuantitativo de la parte subterránea es mucho más costoso y complicado que el estudio de la parte aérea, en especial el estudio de la dinámica de producción y descomposición de raíces gruesas y finas de los árboles. En este trabajo se muestra un ejemplo de análisis de sensibilidad del modelo forestal FORECAST a parámetros que definen la biomasa, longevidad y concentración de nitrógeno en las raíces de los árboles. El modelo se calibró para simular dos rodales de pino silvestre (Pinus sylvestris) en los Pirineos de Navarra. Los resultados indican que la tasa de renovación de raíces finas es el parámetro más influyente en las estimaciones del modelo de crecimiento de los árboles, seguida de la concentración de N en las mismas, siendo la relación biomasa subterránea/total el parámetro al cual el modelo es menos sensible. Además, el modelo es más sensible a los parámetros que definen el componente subterráneo de la biomasa arbórea cuando simula un sitio de menor capacidad productiva y mayor limitación por nutrientes.

Table 1. Radiocarbon dates from TPC522 and box core surface samples from BC521 and BC523

Recent intensification of wind-driven upwelling of warm upper circumpolar deep water (UCDW) has been linked to accelerated melting of West Antarctic ice shelves and glaciers. To better assess the long term relationship between UCDWupwelling and the stability of theWest Antarctic Ice Sheet, we present a multi-proxy reconstruction of surface and bottom water conditions in Marguerite Bay, West Antarctic Peninsula (WAP), through the Holocene. A combination of sedimentological, diatom and foraminiferal records are, for the first time, presented together to infer a decline in UCDW influence within Marguerite Bay through the early to mid Holocene and the dominance of cyclic forcing in the late Holocene. Extensive glacial melt, limited sea ice and enhanced primary productivity between 9.7 and 7.0 ka BP is considered to be most consistent with persistent incursions of UCDW through Marguerite Trough. From 7.0 ka BP sea ice seasons increased and productivity decreased, suggesting that UCDW influence within Marguerite Bay waned, coincident with the equatorward migration of the Southern Hemisphere Westerly Winds (SWW). UCDW influence continued through the mid Holocene, and by 4.2 ka BP lengthy sea ice seasons persisted within Marguerite Bay. Intermittent melting and reforming of this sea ice within the late Holocene may be indicative of episodic incursions of UCDW into Marguerite Bay during this period. The cyclical changes in the oceanography within Marguerite Bay during the late Holocene is consistent with enhanced sensitively to ENSO forcing as opposed to the SWW-forcing that appears to have dominated the early to mid Holocene. Current measurements of the oceanography of the WAP continental shelf suggest that the system has now returned to the early Holocene-like oceanographic configuration reported here, which in both cases has been associated with rapid deglaciation.

1999 University of Michigan Football Team

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Back Row: Paul Schmidt, Mike Gittleson, Mike Elston, Teryl Austin, Brady Hoke, Jim Herrmann, Mike DeBord, Fred Jackson, Bobby Morrison, Stan Parrish, Erik Campbell, Terry Malone, Scot Loeffler, Jon Falk, Scott Draper, Phil Bromley, Jim Schneider

8th Row: Tim Murphy, Dr. Edward Wojtys, Dr. C. Daniel Hendrickson, Kevin Undeen, Mark Borgman, Brian Smalls, Michael Kaselitz, Joe Ghannam, Tommy Huff, Dave Eklund, Rick Brandt, Bob Bland, Mark Ouimet, Kelly Cox, Dennis Coyle, Zach Adami

7th Row: Jason Clyne, Brandon Williams, Greg Brooks, Shantee Orr, Jeremy LeSueur, Carl Biggs, Dave Pearson, Ronald Bellamy, Tyrece Butler, John Navarre, Andy Mignery, Andy Brown, Grant Bowman, Courtney Morgan, Phil Brabbs*, Kyle Blerlein, Chris Roth

6th Row: P.J. Cwayna, TommyJones, Tad Van Pelt, Dwight Mosley, Scott Panique, Stephen Baker, Blake Nasif, Joe Sgroi, Tony Pape, Demeterius Soloman, Norman Boebert, John Spytek, Phil Brackins, B.J. Askew, Charles Drake, Brent Cummings, Ryan Beard, Jon Shaw

5th Row: Aaron Richards, Jason Ptak, Todd Howard, Walter Cross, Julius Curry, Justin Fargas, Bennie Joppru, Dan Rumishek, Dave Petruziello, Shawn Lazarus, Victor Hobson, Dave Armstrong, Deitan Dubuc, Cato June, John Wood, Kyle Froelich, Kirk Moundros

4th Row: Mark Bergin, Cyle Young, Bob Fraumann, Kurt Anderson, Todd Mossa, Rudy Smith, Evan Coleman, Hayden Epstein, Larry Foote, Joe Denay, Drew Henson, Dave Terrell, Marquise Walker, Gary Rose, Michael Manning, Jeremy Miller

3rd Row: Matt Johnson, Ryan Parini, James Whitley, Bill Seymour, Anthony Thomas, Shawn Thompson, Adam Adkins, Jake Frysinger, Ben Mast, Eric Brackins, Eric Rosel, DeWayne Patmon, Dan Williams, Cory Sargent, Brandon Kornblue

2nd Row: Tate Schanski, Jeff Smokevitch, Kevin Bryant, Eric Wilson, Grady Brooks, David Brandt, Steve Frazier, Steve Hutchinson, Jeff Backus, Jason Kapsner, Andy Sechler, Eric Warner, Ken Jackson, Jeff Del Verne

Front Row: Chris Ziemann, Josh Williams, Tom Brady, Patrick Kratus, DiAllo Johnson, Rob Renes, Head Coach Lloyd Carr, Dhani Jones, Ian Gold, Marcus Knight, Tommy Hendricks, Aaron Shea, James Hall

Régina /

Mode of access: Internet.