Effect of Ammonium Sulfate on Absorption of Imazethapyr by Quackgrass (Elytrigia repens) and Maize (Zea mays) Cell Suspension Cultures

Field trials indicated that addition of ammonium sulfate to imazethapyr plus nonionic surfactant increased quackgrass control, especially at low imazethapyr rates. In greenhouse experiments, approximately twice as much imazethapyr was absorbed by quackgrass leaves when the herbicide was applied in combination with nonionic surfactant plus ammonium sulfate than when the herbicide was applied with nonionic surfactant alone. Black Mexican Sweet maize (BMS) suspension-cultured cells were used to evaluate the effects of ammonium sulfate and nonionic surfactant on cellular absorption of imazethapyr in the absence of a cuticular barrier. Imazethapyr absorption by BMS cells was diffusion-mediated, energy-dependent, and exhibited a pH optimum of approximately 3. Over the concentration range of 0.1 to 10.0 μM, the equilibrium concentration of imazethapyr in BMS cells was a linear function of the external concentration. Addition of ammonium sulfate to the external medium of BMS cells enhanced both the rate of imazethapyr uptake and medium acidification. There was a linear correlation between the ability of ammonium sulfate (0.5 to 10 mM) to promote medium acidification and imazethapyr uptake by BMS cells. The ammonium sulfate-induced stimulation of imazethapyr absorption in BMS cells was sensitive to plasma membrane adenosine triphosphatase inhibitors (sodium vanadate, diethylstilbestrol), the uncoupler carbonyl cyanide m-chlorophenylhydrazone, and energy metabolism inhibitors (sodium azide, nitrogen gas), demonstrating that this effect was dependent on ATP production and the functioning of the plasma membrane ATPase. It is hypothesized that cytoplasmic acidification in BMS cells due to ammonium assimilation stimulates the plasma membrane ATPase to pump protons across the plasma membrane which in turn acidifies the cell wall promoting cellular accumulation of imazethapyr by ion-trapping. Cell wall acidification due to ammonium assimilation may contribute to the ability of ammonium sulfate to enhance the efficacy of imazethapyr and other foliar-applied herbicides.

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Parallel secretory pathways to the cell surface in yeast.

The Journal of Cell Biology ◽

10.1083/jcb.131.2.297 ◽

1995 ◽

Vol 131 (2) ◽

pp. 297-310 ◽

Cited By ~ 176

Author(s):

E Harsay ◽

A Bretscher

Keyword(s):

Cell Wall ◽

Plasma Membrane ◽

Double Mutant ◽

Average Diameter ◽

Plasma Membrane Atpase ◽

Membrane Atpase ◽

A Cell ◽

Exocytic Pathway ◽

Two Populations ◽

Wall Components

Saccharomyces cerevisiae mutants that have a post-Golgi block in the exocytic pathway accumulate 100-nm vesicles carrying secretory enzymes as well as plasma membrane and cell-wall components. We have separated the vesicle markers into two groups by equilibrium isodensity centrifugation. The major population of vesicles contains Bg12p, an endoglucanase destined to be a cell-wall component, as well as Pma1p, the major plasma membrane ATPase. In addition, Snc1p, a synaptobrevin homologue, copurifies with these vesicles. Another vesicle population contains the periplasmic enzymes invertase and acid phosphatase. Both vesicle populations also contain exoglucanase activity; the major exoglucanase normally secreted from the cell, encoded by EXG1, is carried in the population containing periplasmic enzymes. Electron microscopy shows that both vesicle groups have an average diameter of 100 nm. The late secretory mutants sec1, sec4, and sec6 accumulate both vesicle populations, while neither is detected in wild-type cells, early sec mutants, or a sec13 sec6 double mutant. Moreover, a block in endocytosis does not prevent the accumulation of either vesicle species in an end4 sec6 double mutant, further indicating that both populations are of exocytic origin. The accumulation of two populations of late secretory vesicles indicates the existence of two parallel routes from the Golgi to the plasma membrane.

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Putative PmrA and PmcA are important for normal growth, morphogenesis and cell wall integrity, but not for viability in Aspergillus nidulans

Microbiology ◽

10.1099/mic.0.080119-0 ◽

2014 ◽

Vol 160 (11) ◽

pp. 2387-2395 ◽

Cited By ~ 7

Author(s):

Hechun Jiang ◽

Feifei Liu ◽

Shizhu Zhang ◽

Ling Lu

Keyword(s):

Cell Wall ◽

Plasma Membrane ◽

Aspergillus Nidulans ◽

Normal Growth ◽

Cell Wall Integrity ◽

Plasma Membrane Atpase ◽

Growth Defects ◽

Double Deletion ◽

Intracellular Ca ◽

P Type

P-type Ca2+-transporting ATPases are Ca2+ pumps, extruding cytosolic Ca2+ to the extracellular environment or the intracellular Ca2+ store lumens. In budding yeast, Pmr1 (plasma membrane ATPase related), and Pmc1 (plasma membrane calcium-ATPase) cannot be deleted simultaneously for it to survive in standard medium. Here, we deleted two putative Ca2+ pumps, designated AnPmrA and AnPmcA, from Aspergillus nidulans, and obtained the mutants ΔanpmrA and ΔanpmcA, respectively. Then, using ΔanpmrA as the starting strain, the promoter of its anpmcA was replaced with the alcA promoter to secure the mutant ΔanpmrAalcApmcA or its anpmcA was deleted completely to produce the mutant ΔanpmrAΔpmcA. Different from the case in Saccharomyces cerevisiae, double deletion of anpmrA and anpmcA was not lethal in A. nidulans. In addition, deletion of anpmrA and/or anpmcA had produced growth defects, although overexpression of AnPmc1 in ΔanpmrAalcApmcA could not restore the growth defects that resulted from the loss of AnPmrA. Moreover, we found AnPmrA was indispensable for maintenance of normal morphogenesis, especially in low-Ca2+/Mn2+ environments. Thus, our findings suggest AnPmrA and AnPmcA might play important roles in growth, morphogenesis and cell wall integrity in A. nidulans in a different way from that in yeasts.

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