Auxin-Growth Relationships in Maize Coleoptiles and Pea Internodes and Control by Auxin of the Tissue Sensitivity to Auxin

Growth of a zone of maize (Zea mays L.) coleoptiles and pea (Pisum sativum L.) internodes was greatly suppressed when the organ was decapitated or ringed at an upper position with the auxin transport inhibitor N-1-naphthylphthalamic acid (NPA) mixed with lanolin. The transport of apically applied 3H-labeled indole-3-acetic acid (IAA) was similarly inhibited by NPA. The growth suppressed by NPA or decapitation was restored by the IAA mixed with lanolin and applied directly to the zone, and the maximal capacity to respond to IAA did not change after NPA treatment, although it declined slightly after decapitation. The growth rate at IAA saturation was greater than the rate in intact, nontreated plants. It was concluded that growth is limited and controlled by auxin supplied from the apical region. In maize coleoptiles the sensitivity to IAA increased more than 3 times when the auxin level was reduced over a few hours with NPA treatment. This result, together with our previous result that the maximal capacity to respond to IAA declines in pea internodes when the IAA level is enhanced for a few hours, indicates that the IAA concentration-response relationship is subject to relatively slow adaptive regulation by IAA itself. The spontaneous growth recovery observed in decapitated maize coleoptiles was prevented by an NPA ring placed at an upper position of the stump, supporting the view that recovery is due to regenerated auxin-producing activity. The sensitivity increase also appeared to participate in an early recovery phase, causing a growth rate greater than in intact plants.

Indole-3-Acetic Acid Controls Cambial Growth in Scots Pine by Positional Signaling1

The vascular cambium produces secondary xylem and phloem in plants and is responsible for wood formation in forest trees. In this study we used a microscale mass-spectrometry technique coupled with cryosectioning to visualize the radial concentration gradient of endogenous indole-3-acetic acid (IAA) across the cambial meristem and the differentiating derivatives in Scots pine (Pinus sylvestris L.) trees that had different rates of cambial growth. This approach allowed us to investigate the relationship between growth rate and the concentration of endogenous IAA in the dividing cells. We also tested the hypothesis that IAA is a positional signal in xylem development (C. Uggla, T. Moritz, G. Sandberg, B. Sundberg [1996] Proc Natl Acad Sci USA 93: 9282–9286). This idea postulates that the width of the radial concentration gradient of IAA regulates the radial number of dividing cells in the cambial meristem, which is an important component for determining cambial growth rate. The relationship between IAA concentration in the dividing cells and growth rate was poor, although the highest IAA concentration was observed in the fastest-growing cambia. The radial width of the IAA concentration gradient showed a strong correlation with cambial growth rate. The results indicate that IAA gives positional information in plants.

Hormonal Control of Parthenocarpic Ovary Growth by the Apical Shoot in Pea1

The role of the apical shoot as a source of inhibitors preventing fruit growth in the absence of a stimulus (e.g. pollination or application of gibberellic acid) has been investigated in pea (Pisum sativum L.). Plant decapitation stimulated parthenocarpic growth, even in derooted plants, and this effect was counteracted by the application of indole acetic acid (IAA) or abscisic acid (ABA) in agar blocks to the severed stump. The treatment of unpollinated ovaries with gibberellic acid blocked the effect of IAA or ABA applied to the stump. [3H]IAA and [3H]ABA applied to the stump were transported basipetally, and [3H]ABA but not [3H]IAA was also detected in unpollinated ovaries. The concentration of ABA in unpollinated ovaries increased significantly in the absence of a promotive stimulus. The application of IAA to the stump enhanced by 2- to 5-fold the concentration of ABA in the inhibited ovary, whereas the inhibition of IAA transport from the apical shoot by triiodobenzoic acid decreased the ovary content of ABA (to approximately one-half). Triiodobenzoic acid alone, however, was unable to stimulate ovary growth. Thus, in addition to removing IAA transport from the apical shoot, the accumulation of a promotive factor is also necessary to induce parthenocarpic growth in decapitated plants.

Higher Activity of an Aldehyde Oxidase in the Auxin-Overproducing superroot1 Mutant of Arabidopsis thaliana1

Aldehyde oxidase (AO; EC 1.2.3.1) activity was measured in seedlings of wild type or an auxin-overproducing mutant, superroot1 (sur1), of Arabidopsis thaliana. Activity staining for AO after native polyacrylamide gel electrophoresis separation of seedling extracts revealed that there were three major bands with AO activity (AO1–3) in wild-type and mutant seedlings. One of them (AO1) had a higher substrate preference for indole-3-aldehyde. This AO activity was significantly higher in sur1 mutant seedlings than in the wild type. The difference in activity was most apparent 7 d after germination, the same time required for the appearance of the remarkable sur1 phenotype, which includes epinastic cotyledons, elongated hypocotyls, and enhanced root development. Higher activity was observed in the root and hypocotyl region of the mutant seedlings. We also assayed the indole-3-acetaldehyde oxidase activity in extracts by high-performance liquid chromatography detection of indole-3-acetic acid (IAA). The activity was about 5 times higher in the extract of the sur1 seedlings, indicating that AO1 also has a substrate preference for abscisic aldehyde. Treatment of the wild-type seedlings with picloram or IAA caused no significant increase in AO1 activity. This result suggested that the higher activity of AO1 in sur1 mutant seedlings was not induced by IAA accumulation and, thus, strongly supports the possible role of AO1 in IAA biosynthesis in Arabidopsis seedlings.

Grasshopper crop and midgut extract effects on plants: an example of reward feedback.

Acid extracts and a resultant fraction from solid-phase extraction (SPE) of Romalea guttata crop and midgut tissues induce sorghum (Sorghum bicolor var. Rio) coleoptile growth in 24-h incubations an average of 49% above untreated controls. When combined with plant auxin, indole-3-acetic acid (IAA), the SPE fraction shows a synergistic reaction, yielding increases in coleoptile growth that average 295% above untreated controls and 8% above IAA standards. The interaction lowered the point of maximum sensitivity of IAA 3 orders of magnitude, resulting in a new IAA physiological set point at 10(-7) g/ml. This synergism suggests that contents in animal regurgitants making their way into plant tissue during feeding may produce a positive feedback in plant growth and development following herbivory. Such a process, also known as reward feedback, may exert major controls on ecosystem-level relationships in nature.

Two auxin-responsive domains interact positively to induce expression of the early indoleacetic acid-inducible gene PS-IAA4/5.

The plant growth hormone indole-3-acetic acid (IAA) transcriptionally activates expression of several genes in plants. We have previously identified a 164-bp promoter region (-318 to -154) in the PS-IAA4/5 gene that confers IAA inducibility. Linker-scanning mutagenesis across the region has identified two positive domains: domain A (48 bp; -203 to -156) and domain B (44 bp; -299 to -256), responsible for transcriptional activation of PS-IAA4/5 by IAA. Domain A contains the highly conserved sequence 5'-TGTCCCAT-3' found among various IAA-inducible genes and behaves as the major auxin-responsive element. Domain B functions as an enhancer element which may also contain a less efficient auxin-responsive element. The two domains act cooperatively to stimulate transcription; however, tetramerization of domain A or B compensates for the loss of A or B function. The two domains can also mediate IAA-induced transcription from the heterologous cauliflower mosaic virus 35S promoter (-73 to +1). In vivo competition experiments with icosamers of domain A or B show that the domains interact specifically and with different affinities to low abundance, positive transcription factor(s). A model for transcriptional activation of PS-IAA4/5 by IAA is discussed.

MEGARA: the future IFU and MOS of the 10.4 M GTC

In these proceedings we summarize the characteristics and current status of MEGARA, the future optical IFU and MOS for the 10.4 m GTC. MEGARA is being built by a Consortium led by the UCM (Spain) that also includes the INAOE (Mexico), the IAA-CSIC (Spain) and the UPM (Spain). The MEGARA IFU offers two different bundles, one called LCB with a field-of-view of 14 x 12 arcsec^2 and a spaxel size of 0.685 arcsec yielding spectral resolutions between R=6000-19000 and another one called SCB covering 10 x 8 arcsec^2 with 0.48 arcsec spaxels and resolutions R=8000-25000. The MOS component allows observing up to 100 targets in 3.5x3.5 arcmin^2. In September 2010 MEGARA was selected as the next optical spectrograph for GTC. Its PDR is scheduled for March 2012 with First Light on 2015.

The Interregional Association Agreement between the European Union and Mercosur: Is the Timing Right? Bruges Political Research Papers 46/2015.

The European Union (EU) and Mercosur talks have been stalled since discussions were resumed in 2000. Recurring protectionist and institutional obstacles have slowed down negotiations. The financial crisis, however, has resulted in low domestic demand in the EU. This has made the interregional association agreement (IAA) with Mercosur more attractive. The loss of the Generalized Scheme of Preference (GSP) status and the lack of a Free Trade Agreement (FTA) with the EU have both disadvantaged Mercosur. A further window of opportunity is opening up in Mercosur. In Brazil, there have been cries for a change in government. In Argentina, presidential elections will take place in October 2015 and will assuredly bring an end to Kirchnerismo. A change in leadership in both countries is expected to make agreement more likely. Protectionist policies are not expected to remain as high if there is change in government. This will provide the EU with an opportunity to advance the negotiations and conclude the IAA.

A guide to the inspection of new houses and houses under construction for conditions which favor attack by wood-inhabiting fungi and insects /

Prepared under interagency agreement IAA-25-75 between USDA Forest Service and Dept. of HUD

The branching gene RAMOSUS1 mediates interactions among two novel signals and auxin in pea

In Pisum sativium, the RAMOSUS genes RMS1, RMS2, and RMS5 regulate shoot branching via physiologically defined mobile signals. RMS1 is most likely a carotenoid cleavage enzyme and acts with RMS5 to control levels of an as yet unidentified mobile branching inhibitor required for auxin inhibition of branching. Our work provides molecular, genetic, and physiological evidence that RMS1 plays a central role in a shoot-to-root-to-shoot feedback system that regulates shoot branching in pea. Indole-3-acetic acid (IAA) positively regulates RMS1 transcript level, a potentially important mechanism for regulation of shoot branching by IAA. In addition, RMS1 transcript levels are dramatically elevated in rms3, rms4, and rms5 plants, which do not contain elevated IAA levels. This degree of upregulation of RMS1 expression cannot be achieved in wild-type plants by exogenous IAA application. Grafting studies indicate that an IAA-independent mobile feedback signal contributes to the elevated RMS1 transcript levels in rms4 plants. Therefore, the long-distance signaling network controlling branching in pea involves IAA, the RMS1 inhibitor, and an IAA-independent feedback signal. Consistent with physiological studies that predict an interaction between RMS2 and RMS1, rms2 mutations appear to disrupt this IAA-independent regulation of RMS1 expression.

Auxin dynamics after decapitation are not correlated with the initial growth of axillary buds

One of the first and most enduring roles identified for the plant hormone auxin is the mediation of apical dominance. Many reports have claimed that reduced stem indole-3-acetic acid (IAA) levels and/ or reduced basipetal IAA transport directly or indirectly initiate bud growth in decapitated plants. We have tested whether auxin inhibits the initial stage of bud release, or subsequent stages, in garden pea (Pisum sativum) by providing a rigorous examination of the dynamics of auxin level, auxin transport, and axillary bud growth. We demonstrate that after decapitation, initial bud growth occurs prior to changes in IAA level or transport in surrounding stem tissue and is not prevented by an acropetal supply of exogenous auxin. We also show that auxin transport inhibitors cause a similar auxin depletion as decapitation, but do not stimulate bud growth within our experimental time- frame. These results indicate that decapitation may trigger initial bud growth via an auxin-independent mechanism. We propose that auxin operates after this initial stage, mediating apical dominance via autoregulation of buds that are already in transition toward sustained growth.

Lack of mycorrhizal autoregulation and phytohormonal changes in the supernodulating soybean mutant nts1007

Autoregulatory mechanisms have been reported in the rhizobial and the mycorrhizal symbiosis. Autoregulation means that already existing nodules or an existing root colonization by an arbuscular mycorrhizal fungus systemically suppress subsequent nodule formation/root colonization in other parts of the root system. Mutants of some legumes lost their ability to autoregulate the nodule number and thus display a supernodulating phenotype. On studying the effect of pre-inoculation of one side of a split-root system with an arbuscular mycorrhizal fungus on subsequent mycorrhization in the second side of the split-root system of a wild-type soybean (Glycine max L.) cv. Bragg and its supernodulating mutant nts1007, we observed a clear suppressional effect in the wild-type, whereas further root colonization in the split-root system of the mutant nts1007 was not suppressed. These data strongly indicate that the mechanisms involved in supernodulation also affect mycorrhization and support the hypothesis that the autoregulation in the rhizobial and the mycorrhizal symbiosis is controlled in a similar manner. The accumulation patterns of the plant hormones IAA, ABA and Jasmonic acid (JA) in non-inoculated control plants and split-root systems of inoculated plants with one mycorrhizal side of the split-root system and one non-mycorrhizal side, indicate an involvement of IAA in the autoregulation of mycorrhization. Mycorrhizal colonization of soybeans also resulted in a strong induction of ABA and JA levels, but on the basis of our data the role of these two phytohormones in mycorrhizal autoregulation is questionable.

Characterization of a strong, constitutive mung bean (Vigna radiata L.) promoter with a complex mode of regulation in planta

We report the cloning and characterization in tobacco and Arabidopsis of a Vigna radiata L. (mung bean) promoter that controls the expression of VR-ACS1, an auxin-inducible ACC synthase gene. The VR-ACS1 promoter exhibits a very unusual behavior when studied in plants different from its original host, mung bean. GUS and luciferase in situ assays of transgenic plants containing VR-ACS1 promoter fusions show strong constitutive reporter gene expression throughout tobacco and Arabidopsis development. In vitro quantitative analyses show that transgenic plants harboring VR-ACS1 promoter-reporter constructs have on average 4-6 fold higher protein and activity levels of both reporter genes than plants transformed with comparable CaMV 35S promoter fusions. Similar transcript levels are present in VR-ACS1 and CaMV 35S promoter lines, suggesting that the high levels of gene product observed for the VR-ACS1 promoter are the combined result of transcriptional and translational activation. All tested deletion constructs retaining the core promoter region can drive strong constitutive promoter activity in transgenic plants. This is in contrast to mung bean, where expression of the native VR-ACS1 gene is almost undetectable in plants grown under normal conditions, but is rapidly and highly induced by a variety of stimuli. The constitutive behavior of the VR-ACS1 promoter in heterologous hosts is surprising, suggesting that the control mechanisms active in mung bean are impaired in tobacco and Arabidopsis. The 'aberrant' behavior of the VR-ACS1 promoter is further emphasized by its failure to respond to auxin and cycloheximide in heterologous hosts. VR-ACS1 promoter regulatory mechanisms seem to be different from all previously characterized auxin-inducible promoters.

Adventitious root formation in Grevillea (Proteaceae), an Australian native species

Grevillea (Proteaceae) is a native Australian plant genus with high commercial value as landscape ornamentals. There has been limited research on the culture and propagation of Australian native species. The effect of indole-3-butyric acid (IBA) on the rooting of G. 'Royal Mantle' and G. 'Coastal Dawn' in winter, spring and summer was evaluated at University of Queensland Gatton, Southern Queensland in order to determine the rooting ability of this species in different seasons. Both Grevillea cultivars showed seasonal rooting. The more difficult-to-root G. 'Coastal Dawn' had a reduced response to IBA application than G. 'Royal Mantle'. Stem and leaf indole-3-acetic acid (IAA) levels were not different between cultivars, therefore rooting ability between the two cultivars does not appear to be due to the differences in endogenous IAA levels. (c) 2005 Elsevier B.V. All rights reserved.

A configuração do circuito espacial de produção sucroalcooleira em Alagoas

The sugarcane production consists in the principal product activity in the state of Alagoas, holding a structure composed of 25 unities of production that represents the economic base of more than a half of its municipies, what make it be the biggest producer of the sector in North and Northwest, exporting its products for countries in different continents. From this reference, it was searched in the present work, to understand the configuration of the circuit space production of sugar cane in Alagoas, from the use of the territory, trough the analyses of the more significant events related to the sector, and, the established rules by the State, through the government, by organs like Institute of Sugar and Alcohol (IAA), and programs like National Alcohol Program (Proálcool), between others, that had as function to structure and to allocate resources to the sugar cane sector. It was realized that the investments done made possible the renovation of techniques used in the sugar cane complex. In the beginning, with the substitution of the mill for factories and, afterwards, the improvement of the agriculture and factory process themselves, improving the utilization of the byproduct, and the productive integration of instances, specially with the sugar, cane, electricity generation production, intensifying the participation of the state in the internation division of labor, giving it a organization structure divided by big hegemonic agents of this process. SO, the sugar cane geographic configuration existing in alagoano territory was restructured and the circuit even more pass to constitute movement of many scales, subsidized by cooperation circles. However, this configuration showed itself subservient to world commerce, what conditions the adoption of hegemonic practices that are far from the local projects and living practices. The verticality imposed offers a configuration that isn’t peculiar, that only serves to answer to the big hegemonic agent commands, characterizing the continuity of the present capitalism process. It means that the sugar cane factories use corporately the territory as resource to obtain more lucrativity and this way dominate the bigger quantity of consumer commerce