Production Of Stress Ethylene Research Articles

Enhancement of growth and salt tolerance of rice seedlings by ACC deaminase-producing Burkholderia sp. MTCC 12259

Increasing soil salinity is often associated with accelerated ethylene production in plants, leading to overall growth reduction. The salt-tolerant 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase-producing PGPR may alleviate salt stress by reducing the production of stress ethylene. In this study, a salt-tolerant ACC deaminase-producing strain named P50 was isolated from a coastal rice field in Odisha, India, which enhanced the growth of rice seedlings under salt stress. The P50 strain was identified as Burkholderia sp. based on phenotypic characteristics, MALDI-TOF MS data for ribosomal proteins and 16S rDNA sequence-based homology. Various PGP traits of strain P50 were characterized, among which the ACC deaminase activity was optimized at different physical conditions and confirmed by enzyme assay, as well as FTIR. The IAA, EPS and proline production of this strain were estimated under increasing NaCl concentrations essential for plant growth promotion under salt stress. Finally, the P50 strain was utilized in a gnotobiotic assay using rice seedlings (cv. Swarnamasuri) under saline stress. Seedlings treated with the P50 strain showed improvement in various morphological and biochemical characteristics, ROS scavenging antioxidant enzymatic activities, and reduced amounts of stress ethylene compared to non-inoculated strains under salinity. In addition, isolation of the ACC deaminase mutant of this strain was not found to reduce stress ethylene, confirming that the P50 strain was associated with a reduction in stress ethylene. Strain P50 was also found to colonize the root surfaces of rice seedlings associated with the plant-microbe interaction process. Thus, as an effective salt-tolerant PGPR, strain P50 can be utilized in salt-affected agricultural fields to improve plant growth in a sustainable manner.

ACC-Deaminase-Producing Endophyte Brachybacterium paraconglomeratum Strain SMR20 Ameliorates Chlorophytum Salinity Stress via Altering Phytohormone Generation

The higher content of salt in soil is the key constraint to crop productivity. Induction of stress ethylene production from 1-aminocyclopropane-1-carboxylate (ACC) in the plant system is one of the consequences of salt stress responsible for toxicity to the plant. Several transgenic plants have been developed by expressing the ACC deaminase bacterial gene as a stress management strategy which apart from being a costly proposition lacks public acceptability. Our main objective was to investigate if a plant inoculated with ACC-deaminase-producing bacterial endophyte will effectively mitigate salt-induced damage and act as an alternative to transgenics. An ACC deaminase-producing salt-tolerant endophyte SMR20 (Brachybacterium paraconglomeratum) was isolated from the roots of Chlorophytum borivilianum, a medicinal plant sensitive to salt stress. Initially we tested ACC-deaminase-producing SMR20 for amelioration of salt stress-induced damage at three different concentrations of salt, that is, 0, 75, 100 and 150 mM NaCl. 150 mM salt stress was selected for further study because wider differences between inoculated and uninoculated plants were noticed under this concentration of NaCl stress. Inoculated with SMR20 successfully protected C. borivilianum from salt stress-induced crop losses. SMR20 significantly alleviated the negative impact of salinity by potential deamination of ACC (precursor for ethylene generation) in the host Chlorophytum roots leading to decreased production of stress ethylene, delayed chlorosis and senescence that resulted in improved yield of plants. Apart from reducing stress ethylene, the presence of the endophyte also affected other phytohormone quantities like indole-3-acetic acid and abscisic acid in plants. It also altered the amount of total leaf pigments and biochemical compounds like proline, malondialdehyde and enhanced foliar nutrient uptake. Due to these outcomes, it appears that an ACC-deaminase-producing endophyte can enhance crop tolerance against salinity stress and can be an important area to explore.

ACC Deaminase Producing Arsenic Tolerant Bacterial Effect on Mitigation of Stress Ethylene Emission in Maize Grown in an Arsenic Polluted Soil

Arsenic is a known hazardous metalloid not only to the animals but also to plants. With high concentrations, it can impede normal plant growth and cause even death of plants at extremely high levels. A known plant response to stress conditions such as toxic levels of metal (loids) is the production of stress ethylene, causing inhibitory effect on root growth in plants. When the effect of various arsenic concentrations was tested to maize plant, the stress ethylene emission proportionately increased with increasing concentration of As(V). The inoculation of two arsenic tolerant bacteria; Pseudomonas grimonti JS126 and Pseudomonas taiwanensis JS238 having respective high and low 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity reduced stress ethylene emission by 59% and 30% in maize grown in arsenic polluted soils. The result suggested the possible use of Pseudomonas grimonti JS126 for phytoremediation of arsenic polluted soils.

Identification of a novel multiple environmental factor-responsive 1-aminocyclopropane-1-carboxylate synthase gene, NT-ACS2, from tobacco

Many abiotic environmental factors elicit the production of stress-ethylene in higher plants. To elucidate the molecular mechanisms underlying the regulation of stress-ethylene production and the physiological roles played by stress-ethylene in stress responses of plants, we studied the gene expression of ACC synthase in tobacco plants that had been subjected to environmental stresses. Four new tobacco ACC synthase cDNA fragments, NT-ACS2, NT-ACS3, NT-ACS4 and NT-ACS5, were identified and sequenced. It was found that NT-ACS2 could be induced by wounding, cold temperature and, especially, sunlight. NT-ACS4 was induced at a faster kinetics by wounding. The multiple environmental stress-responsive (MESR) NT-ACS2 gene was found to contain three introns and four exons and encode a polypeptide of 484 amino acids, 54·6 kDa and pI 6·87. Computer analysis of the 3·4 kb 5′ flanking region upstream of the ACS coding region revealed the existence of a group of putative cis-acting regulatory elements potentially conferring wounding, chilling, and UV light inducibility. Phylogenetic analysis of ACC synthase genes of different plant origins indicated that the chill-inducible NT-ACS2 gene is closely related to a chilling-inducible citrus ACS gene.

The Influence of Air Pollution on the Concentration of Airborne Elements and on the Production of Stress-Ethylene in the Lichen Usnea hirta (L.) Weber em. Mot. Transplanted in Urban Sites in Oulu, N. Finland

The purpose of the present study was to examine theresponse, as indicated by the production of stress-ethylene, of the lichenUsnea hirta, to a buffered acidic solution and to a solutioncontaining bisulfite ion, both at pH 4.0. In addition, the study investigatedthe accumulation capacity of U. hirta transplanted either to thevicinity of two streets with slow traffic, or to the vicinity of a highway inthe city of Oulu, N. Finland for a short period (45 d), and to analyze thecomparative production of stress-ethylene and the amounts of airborneelements accumulated in the thallus. Thalli of U. hirta manifested ahigh accumulation capacity for K, Ca, Na, Mg, Fe, Zn, and Mn in samplesexposed in one of the two streets with slow traffic in Oulu, in comparisonwith thalli left at the control site in the forest outside of the city. Twoof the observed elements, Pb and Ca, exhibited a positive correlation withthe concentration of ethylene detected consecutive to the treatment of lichenthalli with H2O (pH 6.8). The concentrations of stress-ethylene inlichen thalli retrieved from the streets with slow traffic and less cars(14,000 per day), soaked in solutions of NaHSO3 (pH 4.0), werehigher than those produced by thalli retrieved from a site near the highway(with 25,000 cars per day) and by thalli left in the forest. It is suggestedthat the streets with slow traffic and less cars are more polluted than thehighway as a result of bad ventilation conditions and a slow rate ofdispersion of airborne pollutants.

Differential Responses of Certain Lichen Species to Sulfur-Containing Solutions Under Acidic Conditions as Expressed by the Production of Stress-Ethylene

To determine whether fluctuations in the concentration of ethylene produced by lichens exposed to sulfur-containing solutions at a low pH correlate with the tolerance/sensitivity of these lichens to air pollution, we measured the amount of ethylene produced by thalli soaked in H2SO4 and NaHSO3. The exposure of Hypogymnia physodes, Cladina stellaris, and Bryoria fuscescens to H2SO4 at a pH ranging between 4.0 and 2.0 did not produce changes in the concentration of ethylene in comparison with samples wetted with H2O at pH 6.8. The exposure of two pendulous lichens, Usnea hirta and Alectoria sarmentosa, to 1.0 and 5.0 mM H2SO4 at pH 2.7 and 2.0, respectively, stimulated only a slight increase of ethylene production, whereas another pendulous lichen, Bryoria fremontii, exposed to H2SO4 at pH 4.0-2.0 decreased its production of ethylene. The soaking of H. physodes, U. hirta, C. stellaris, and A. sarmentosa thalli in NaHSO3 at pH 4.0 gradually increased the production of ethylene. The exposure of B. fremontii and B. fuscescens to low NaHSO3 concentrations depressed the production of ethylene in these lichens. The indifference of H. physodes to H2SO4 under strong acidic conditions correlated with its resistance to SO2 in the air. In accordance with a model by D. M. Reid (In "Effects of Atmospheric Pollutants on Forests, Wetlands and Agricultural Ecosystems" (T. C. Hutchinson and K. M. Meema, Eds.), Vol. G 16, pp. 241-245. NATO ASI Series, Springer-Verlag, Berlin and Heidelberg, 1987) referring to higher plants, it is suggested that sulfur-containing solutions under acidic conditions increase the solubility of particles containing heavy metals entrapped among the mycobiont hyphae in lichens. This may lead to an increase of the production of endogenous ethylene in lichens as they are exposed to sulfur-containing chemicals, to acidic rain, or to heavy metal-polluted air.

The effect of ethylene on phenylalanine ammonia lyase (PAL) induction by a fungal elicitor in Phaseolus vulgaris

The effects of ethylene on the induction of phenylalanine ammonia-lyase (PAL) by cell wall elicitors of Colletotrichum lindemuthianum was investigated in leaves of susceptible and resistant cultivars of Phaseolus vulgaris (cultivars Pinto and Kievit respectively). Induction of PAL by exogenously supplied ethylene and associated test substances alone, without elicitor, was negligible. With elicitor alone, cv. Kievit responded to lower concentrations than cv Pinto. Exogenously supplied ethylene augmented the response of cv. Kievit only in the presence of limiting concentrations of elicitor. When concentrations of elicitor giving maximum PAL induction were used, ethylene was without effect in cv. Kievit also. Aminoethoxyvinylglycine (AVG) partially inhibited the induction of PAL in cv. Kievit and this inhibition could be reversed by aminocyclopropane-1-carboxylic acid (ACC) and ethylene. However, since cv. Pinto did not respond to ethylene, the application of AVG in the presence of elicitor was, as expected, without effect. Unless introduced within 2 h of elicitor application, ethylene was without effect on PAL production in cv. Kievit also; likewise, the inhibitory effect of AVG was minimal if not injected within the same time period following elicitor. Elicitor rapidly induced the synthesis of ACC during this 2 h period leading to the production of stress ethylene and this was completely inhibited by AVG and completely reversed by ACC. The effect of the elicitor, after injection into the leaf of cv. Kievit, was to change both the distribution and relative concentrations of the soluble proteins. Ethylene enhanced this effect and the 40 % increase in PAL activity observed in the presence of the hormone can largely be accounted for by the increase in the concentration of the enzyme. Changes brought about by the elicitor were eliminated by inhibitors of protein and nucleic acid synthesis, the effects of which could not be reversed by ethylene. These results are discussed in relation to other studies. It has been proposed that elicitors induce the biosynthesis of ethylene and PAL independently. Ethylene is involved in the activation of the induced response leading to the synthesis of PAL, and thereby phytoalexins, particularly when the response to elicitor is sub-optimal.

Cotton Fleahopper and Associated Microorganisms as Components in the Production of Stress Ethylene by Cotton

Excised cotton terminal buds incubated with adults or nymphs of the cotton fleahopper (CFH), Pseudatomoscelis seriatus (Reuter), produced ethylene at theoretical abscission-inducing rates by 24 h after introduction of the insect. Inoculation of cotton shoot tips with three microorganisms commonly associated with CFH and cotton in all cases promoted ethylene production to theoretical abscission-inducing rates by 24 h after inoculation. CFH alone or injection of microorganisms consistently caused cotton shoot tips to darken and become soft. These changes paralleled the rise in ethylene production and did not occur in control shoot tips. Of the three microorganisms, Xanthomonas campestris pv malvacearum (Smith) Dye (XCM) produced little ethylene when grown in culture, while the two fungi, Penicillium purpurogenum Stoll and P. glabrum (Wehmer) Westling, produced higher levels. The parallel between plant response to CFH, XCM, and CFH + XCM suggests a similar mechanism of ethylene induction by these two stress agents. Since a portion of the CFH were devoid of microorganisms, yet their impact on ethylene production by cotton tissue was uniform, we propose that the primary mechanism of ethylene induction involves the insect's salivary fluids which contain cell wall hydrolyzing enzymes.

Effect of chlorine on stress ethylene production

Several plant species were exposed to chlorine to determine whether stress ethylene was induced. Increasing the chlorine concentration or duration of exposure increased stress ethylene production until a maximum level was reached; either a higher concentration or longer duration decreased ethylene production below the maximum. The production of stress ethylene persisted less than 24 hr following exposure. Stress ethylene increased prior to visual injury but it was associated with visual injury. However, low concentrations of chlorine that did not cause visual injury elicited stress ethylene formation, suggesting that stress ethylene production is a more sensitive measure of chlorine stress than foliar injury.