Influence of Enol Ether Amino Acids, Inhibitors of Ethylene Biosynthesis, on Aminoacyl Transfer RNA Synthetases and Protein Synthesis

Enhanced ethylene production and leaf epinasty are characteristic responses of tomato (Lycopersicon escukntum Mill.) to waterlogging. It has been proposed (Bradford, Yang 1980 Plant Physiol 65: 322-326) that this results from the synthesis of the immediate precursor of ethylene, 1-aminocyclopropane-I-carboxylic acid (ACC), in the waterlogged roots, its export in the transpiration stream to the shoot, and its rapid conversion to ethylene. Inhibitors of the ethylene biosynthetic pathway are available for further testing of this ACC transport hypothesis: aminooxyacetic acid (AOA) or aminoethoxyvinylglycine (AVG) block the synthesis of ACC, whereas CO2 prevents its conversion to ethylene. AOA and AVG, supplied in the nutrient solution, were found to inhibit the synthesis and export of ACC from anaerobic roots, whereas Co2" had no effect, as predicted from their respective sites of action. Transport of the inhibitors to the shoot was demonstrated by their ability to block wound ethylene synthesis in excised petioles. Al three inhibitors reduced petiolar ethylene production and epinasty in anaerobically stressed tomato plants. With AOA and AVG, this was due to the prevention of ACC import from the roots as well as inhibition of ACC synthesis in the petioles. With Co21, conversion of both root-and petiole-synthesized ACC to ethylene was blocked. Collectively, these data support the hypothesis that the export of ACC from low 02 roots to the shoot is an important factor in the ethylene physiology of waterlogged tomato plants.Ethylene is an important endogenous regulator of plant responses to waterlogging (7,14). Under the low 02 conditions in the soil during flooding, tomato roots synthesize ACC,3 the immediate precursor of ethylene, and transport it in the xylem to the shoot, where it is rapidly converted to ethylene (8,9). This increase in the ethylene content of the shoot tissues results in petiole epinasty, aerenchyma formation, and other anatomical and morphological responses associated with waterlogging (6,11,14).The sites of inhibition in the biosynthetic pathway of ethylene are now known for several inhibitors. Application of these inhibitors allows further tests of the role of root-synthesized ACC in shoot responses to waterlogging. AOA and AVG effectively prevent the conversion of SAM to ACC, both in vivo (1,22,23) conversion of ACC to ethlene. Co2" on the other hand, has no effect on ACC synthesis but inhibits the formation of ethylene from ACC (23). These compounds, therefore, permit inhibition of ethylene biosynthesis at specific steps in the pathway (see 18, 19, for reviews). In waterlogged plants, the locations of stress-induced ACC synthesis and its conversion to ethylene are separated spatially, with the formation of ACC from SAM occurring in the roots and conversion of ACC to ethylene occurring in the shoot.Thus, the effects of application of AOA, AVG, or Co2" to anaerobic roots should reflect their differing sites of action. In this study, these inhibitors were used to further characterize th...

Section: Resultsmentioning

confidence: 99%

Inhibition of Ethylene Synthesis in Tomato Plants Subjected to Anaerobic Root Stress

Bradford

Hsiao²,

Yang³

1982

“…AVG was obtained through the courtesy of Dr. G. Lee Benson, Maag Agrochemicals, HLR Sciences, Inc., Vero Beach, FL, and from samples kindly provided by Dr. Richard Gladon, Department of Horticulture, Iowa State University. In all cases, AVG was used at 10-6 M. This is below the concentration (10-4 M) at which AVG begins to inhibit protein synthesis (11), and, in fact, we find that 10-6 M AVG promotes root growth slightly (15).…”

Section: Methodsmentioning

confidence: 98%

Promotion of Growth and Hydrogen Ion Efflux by Auxin in Roots of Maize Pretreated with Ethylene Biosynthesis Inhibitors

Mulkey¹,

Kuzmanoff²,

Evans³

1982

Low concentrations of auxin (e.g. 10(-10)m) do not promote the growth of intact seedling roots of maize (Zea mays L. Bear Hybrid WF 9 x 38). Higher concentrations are inhibitory. When the roots are pretreated with the ethylene biosynthesis inhibitors, cobalt and aminoethoxyvinylglycine, auxin (10(-10) to 10(-8)m) strongly promotes their growth. The promotion of growth by auxin in pretreated roots is preceded by enhanced hydrogen ion secretion from the roots. The data indicate that hormone-enhanced hydrogen ion secretion may play a role in the rapid promotion of root growth by auxin. The ability of auxin to promote the growth of intact roots is discussed in relation to the Cholodny/Went hypothesis of hormonal control of root geotropism.

“…6); hydroxyproline and proline deposition in the cell wall were simultaneously inhibited by 21 and 22%, respectively. It has been demonstrated by Mattoo et al (18) that protein synthesis is not affected when AVG is used at concentrations ranging up to lo-4 M. Although sharing common structural features with canaline, AVG was more efficient at low concentrations since both ethylene and hydroxyproline were only slightly affected upon incubation with l0-5 M L-Can.…”

Section: )mentioning

confidence: 96%

Cell Surfaces in Plant-Microorganism Interactions

Toppan¹,

Roby²,

Esquerré-Tugayé³

1982

MATERIALS AND METHODSEthylene production and cell wail hydroxyproline-rich glycoprotein (HRGP) biosynthesis are greatly enhanced in melon (Cucumin melo cv.Cantaloup charentais) seedlings infected with CoUetotrichum lagenariwm.Short-term experiments performed in the presence of specific inhibitors of the ethylene pathway from methionine, namely L-canaline and aminoethoxyvinylglycine, indicate that under non-toxic conditions, both ethylene and I'4Clhydroxyproline deposition in the cell wall of infected tissues are significantly lowered. On the contrary, treatment of healthy tissues with 1-aminocyclopropane 1-carboxylic acid, a natural precursor of ethylene, stimulates both the production of the hormone and the incorporation of I'Clhydroxyproline into cell wall proteins.The data provide the first evidence of the in vivo effect of ethylene on the cell wall hydroxyproline-rich glycoprotein biosynthesis in plants.It has been reported in previous papers (10, 11) that melon seedlings respond to a fungal attack by the accumulation of HRGP2 in their cell walls. Special attention has been paid to this modification of the cell surface for it involves glycoproteins, a class of components often mediating cell to cell interactions (5). Availability of plants with higher or lower than normal amounts of cell wall hydroxyproline allowed us to ascertain that the enrichment of diseased plants in HRGP is closely associated to their defense against microorganisms (9). Indirect evidence suggests a role for ethylene in the regulation of this mechanism. When supplied exogenously to intact plants, this hormone promotes an enrichment of the cell wall in hydroxyproline (24) corresponding to an enrichment in HRGP (9). A similar hydroxyproline response occurs after wounding of plant tissues (7), a process otherwise well-known to stimulate the production ofethylene (13). Inasmuch as large amounts of this hormone are often released by infected plants (1,22) Patil and Tang (21), and then diluted to appropriate concentrations with 50 mm phosphate buffer (pH 6.0). AVG and ACC were each dissolved and adjusted to I x lo-3 M in 50 mm phosphate buffer (pH 6.0). Appropriate dilutions were then made with the same buffer.Ethylene Measurement. The production of ethylene was measured from excised seedlings, petiole of the first leaf, and from C. lagenarium, as follows. Four excised seedlings (without roots) were enclosed for 24 h in 570-ml serum flasks stopped with serum caps, and containing 30 ml of the usual growth medium (28). Newly excised seedlings were used everyday. The petioles were cut into 5-mm segments as previously indicated (9), and divided into lots of 2 g. The segments of each lot were incubated for 4 h under the light in 13 ml serum vials, stopped with serum vaccine caps, containing 6 ml of a medium consisting of 2% sucrose in 50 mm K-phosphate buffer (pH 6.0). A CO2 trap made of filter paper soaked with 200 td of 1 N KOH was inserted into each vial.Measurements of ethylene from C. lagenarium were performed on a 6-d-old culture i...