Strategies used by rhizobia to lower plant ethylene levels and increase nodulation

2002 ◽  
Vol 48 (11) ◽  
pp. 947-954 ◽  
Author(s):  
Wenbo Ma ◽  
Donna M Penrose ◽  
Bernard R Glick

Agriculture depends heavily on biologically fixed nitrogen from the symbiotic association between rhizobia and plants. Molecular nitrogen is fixed by differentiated forms of rhizobia in nodules located on plant roots. The phytohormone, ethylene, acts as a negative factor in the nodulation process. Recent discoveries suggest several strategies used by rhizobia to reduce the amount of ethylene synthesized by their legume symbionts, decreasing the negative effect of ethylene on nodulation. At least one strain of rhizobia produces rhizobitoxine, an inhibitor of ethylene synthesis. Active 1-aminocyclopropane-1-carboxylate (ACC) deaminase has been detected in a number of other rhizobial strains. This enzyme catalyzes the cleavage of ACC to α-ketobutyrate and ammonia. It has been shown that the inhibitory effect of ethylene on plant root elongation can be reduced by the activity of ACC deaminase.Key words: rhizobia, nodulation, ethylene, ACC deaminase, rhizobitoxine.

Endocrinology ◽  
2005 ◽  
Vol 146 (3) ◽  
pp. 1532-1540 ◽  
Author(s):  
Anne Florin ◽  
Magali Maire ◽  
Aline Bozec ◽  
Ali Hellani ◽  
Sonia Chater ◽  
...  

In the present study we investigated whether fetal exposure to flutamide affected messenger and protein levels of claudin-11, a key Sertoli cell factor in the establishment of the hemotesticular barrier, at the time of two key events of postnatal testis development: 1) before puberty (postnatal d 14) during the establishment of the hemotesticular barrier, and 2) at the adult age (postnatal d 90) at the time of full spermatogenesis. The data obtained show that claudin-11 expression was inhibited in prepubertal rat testes exposed in utero to 2 and 10 mg/kg·d flutamide. However, in adult testes, the inhibition was observed only with 2, and not with 10, mg/kg·d of the antiandrogen. It is shown here that these differences between prepubertal and adult testes could be related to dual and opposed regulation of claudin-11 expression resulting from positive control by androgens and an inhibitory effect of postmeiotic germ cells. Indeed, testosterone is shown to stimulate claudin-11 expression in cultured Sertoli cells in a dose- and time-dependent manner (maximum effect with 0.06 μm after 72 h of treatment). In contrast, postmeiotic germ cells potentially exert a negative effect on claudin-11 expression, because adult rat testes depleted in spermatids (after local irradiation) displayed increased claudin-11 expression, whereas in a model of cocultured Sertoli and germ cells, spermatids, but not spermatocytes, inhibited claudin-11 expression. The apparent absence of claudin-11 expression changes in adult rat testes exposed to 10 mg/kg·d flutamide therefore could result from the antagonistic effects of 1) the inhibitory action of the antiandrogen and 2) the stimulatory effect of the apoptotic germ cells on claudin-11 expression. Together, due to the key role of claudin-11 in the hemotesticular barrier, the present findings suggest that such regulatory mechanisms may potentially affect this barrier (re)modeling during spermatogenesis.


1998 ◽  
Vol 28 (3) ◽  
pp. 396-401 ◽  
Author(s):  
Simon M Landhäusser ◽  
Victor J Lieffers

Three experiments were conducted to examine the effects of Calamagrostis canadensis (Michx.) Beauv. on the growth of Populus tremuloides Michx. Containerized seedlings of P. tremuloides were transplanted into large pots and subjected to (1) three soil temperatures (20, 12, and 6°C), (2) root competition with C. canadensis, or (3) presence or absence of C. canadensis litter, each at two nutrient regimes. In the first experiment, significant differences (p = 0.0001) in pre- and neo-formed leaf area and root and shoot dry weights were observed for plants subjected to the three different soil temperatures. In experiment two, the presence of C. canadensis significantly (p < 0.001) reduced total biomass, plant height, and root collar calliper of P. tremuloides. In the third experiment, a significant interaction (p = 0.027) between C. canadensis litter and nutrient regime was observed, with the greatest inhibitory effect on P. tremuloides growth resulting from litter at the low nutrient regime. Low soil temperature had the strongest negative effect on P. tremuloides of the four factors investigated. However, direct competition with C. canadensis, low nutrient conditions, and C. canadensis litter likely would add to the growth suppression of P. tremuloides by this grass. The results of this study have significant implications for the management of P. tremuloides after harvesting.


Planta ◽  
1985 ◽  
Vol 164 (3) ◽  
pp. 406-414 ◽  
Author(s):  
J. C. Meeks ◽  
C. S. Enderlin ◽  
C. M. Joseph ◽  
J. S. Chapman ◽  
M. W. L. Lollar

1975 ◽  
Vol 78 (3) ◽  
pp. 442-450 ◽  
Author(s):  
J. Pelletier ◽  
R. Ortavant

ABSTRACT The intensity of negative feedback of androgens on hypothalamo-hypophyseal activity was compared in two groups of castrated rams under 8.00 or 16.00 h of daily illumination respectively following a conditioning period. In experiment I, two groups of 15 rams under each light photoperiod were slaughtered at different times after a 200 mg testosterone propionate (TP) intramuscular injection. Animals receiving the vehicle only acted as controls. The hypophyseal LH concentration, which increases when there is temporary inhibition of the release into the blood, was taken as a criterion of the inhibition due to TP. In both groups of rams the LH concentration increased in the pituitary following TP treatment. A return to the pre-injection level was observed 48 h later only in animals under a 8.00 h light photoperiod, indicating a shorter negative effect of the injection than in the case of rams under 16.00 h light photoperiod. In experiment II, the inhibitory effect of TP was assessed at two doses, i. e. 300 and 600 mg, by the decrease in the plasma LH level following an intramuscularly injection. In both cases the decrease in LH release was more pronounced in rams under 16.00 h of daily illumination than in those under 8.00 h (mean decrease in LH release: 21.2 and 33.2% respectively in 300 and 600 mg treated rams under 16.00 h daylight as against 9.2 and 14.8% in rams under 8.00 h). Thus it appears that to the intrinsic action of the photoperiod is superposed on a modulatory effect of steroid action on the hypothalamo-hypophyseal activity. The hypothesis is therefore presented that, in rams a decreasing light photoperiod acts in two ways: by stimulating the activity of the hypothalamo-hypophyseal system, by decreasing the intensity of the negative feedback effect of steroids.


2006 ◽  
Vol 84 (9) ◽  
pp. 1405-1416 ◽  
Author(s):  
Shiv T. Hiremath ◽  
Sujata Balasubramanian ◽  
Jun Zheng ◽  
Gopi K. Podila

The ectomycorrhiza is a symbiotic organ generated from the intricate association of fungal hyphae and plant root. The establishment of the ectomycorrhiza is a coordinated process of cross-talk between plant and fungus, followed by metabolic, developmental, and structural changes in the fungus, resulting in its growth toward the root. The initial stages of the symbiotic association are significant, since the direction of the association is determined by the gene expression level shifts that occur at this time. We have isolated a Laccaria bicolor (Maire) Orton cDNA clone corresponding to acetyl-CoA acetyltransferase (Lb-AAT), which is expressed during interaction with red pine roots and is symbiosis regulated. Acetyl-CoA acetyltransferase (EC 2.3.1.9) is an enzyme of the β-oxidation pathway that degrades long-chain fatty acids to acetyl-CoA. Expression of Lb-AAT is regulated by plant presence, by glucose, and by the presence of acetate or oleate in the medium. It is proposed that the role of Lb-AAT in the symbiosis is generation of two carbon compounds from stored lipids and generation of acetoacetyl-CoA in early interaction facilitating net growth from existing cell material. These results coupled with recent microarray analysis that revealed coordinated expression of malate synthase and other lipid metabolism genes along with Lb-AAT, suggest that this role for Lb-AAT could be an important part of preinfection process in ectomycorrhizal symbiosis and in the transfer and utilization of the carbon in the fungus.


2021 ◽  
Author(s):  
Shuhong Wang ◽  
Hanxue Chen ◽  
Kedong Yin

Abstract The employment effect of enterprises embedded in global value chains has important theoretical value, but existing research has ignored the impact of cross-border pollution transfer on employment under the division of labor system within the value chain. This study constructs a global environmental value chain (GEVC) analysis framework to combine economic and environmental issues and establishes a theoretical model to discuss the impact of the degree of enterprise embeddedness in the GEVC on employment. Using 2000–2006 data from the China Industry Business Performance and China Customs databases, the study finds that an increase in the degree of enterprise embeddedness has a significant inhibitory effect on employment, especially for female laborers, lower-skilled laborers, state-owned enterprises, private enterprises, and enterprises in the eastern region. The research also shows that the cost increase effect enhances the negative effect of increased GEVC embeddedness on employment, while the innovation promotion effect and the foreign direct investment effect serve to mitigate the negative effect. The results provide a reference for developing countries seeking to effectively protect people's livelihood and employment while achieving a leap in the division of labor along the green value chain.


2019 ◽  
Vol 39 (1) ◽  
Author(s):  
Ibomcha Ngangom ◽  
M. M. Nisha ◽  
S. Santhosh Kumar ◽  
K. V. Ravindra ◽  
Leela Tewari ◽  
...  

Plants produce a wide range of organic compounds like sugars, organic acids and vitamins, which can be used as nutrients or signals by microbial populations. On the other hand, microorganisms release phytohormones, enzymes, which may act directly or indirectly to activate plant immunity and regulate plant growth. Plant signalling molecules such as auxin and cytokinin can be produced by microorganisms to colonize efficiently with roots and enhance root activity. The isolated microbe Bacillus aryabhattai, has the ability to produce1-aminocyclopropane-1-carboxylate (ACC) deaminase to lower plant ethylene level, often a result of various stresses, and is found to be a key component in the efficacious functioning of this bacterium. The optimal functioning of this bacterium includes the synergistic interaction between ACC deaminase, and plant with bacterial indole-3-acetic acid (IAA).


Author(s):  
V.YU. DENISENKO

Соединения, для которых отсутствуют необходимые рецепторы на поверхности клеток, не способны проникать внутрь клеток. Для обеспечения их поступления в клетки используются различные методы (пермеабилизация, инъекция этих соединений внутрь клетки и т. д.). Однако эти способы дорогостоящие в применении, либо оказывают на клетки эффект, не совместимый с дальнейшей жизнедеятельностью. Вход в нагруженные флуоресцентными зондами хлортетрациклин (ХТЦ) и Фура-2АМ клетки гранулезы коров различных соединений вызывает изменение концентрации цитоплазматического и запасенного во внутриклеточных депо кальция. В интактных нагруженных ХТЦ клетках гранулезы добавление пролактина (ПРЛ) стимулировало освобождение Са2 из внутриклеточных депо. В необработанных клетках гепарин не способен самостоятельно проникать в клетки. Для обеспечения входа гепарина в клетки используется процедура пермеабилизации, то есть клетки предварительно обрабатываются детергентом (дигитонином). Использование гепарина приводило к ингибированию освобождения Са2 из внутриклеточных депо, стимулированного добавлением ПРЛ. Обработка клеток детергентом дигитонином не оказывала влияния на стимулированное ПРЛ освобождение Са2 из депо и ингибирующее действие гепарина на выход Са2 из внутриклеточных депо. В интактных нагруженных Фура-2АМ клетках гранулезы добавление ПРЛ не приводило к увеличению концентрации цитоплазматического кальция.После обработки дигитонином нагруженных Фура-2АМ клеток гранулезы внесение ПРЛ приводило к увеличению концентрации цитоплазматического Са2, которое ингибировалось при добавлении гепарина. Полученные данные позволяют предположить, что ХТЦ образует поры на поверхности клеток гранулезы, способствуя таким образом проникновению в клетки различных соединений.Соединения, для которых отсутствуют необходимые рецепторы на поверхности клеток, не способны проникать внутрь клеток. Для обеспечения их поступления в клетки используются различные методы (пермеабилизация, инъекция этих соединений внутрь клетки и т. д.). Однако эти способы дорогостоящие в применении, либо оказывают на клетки эффект, не совместимый с дальнейшей жизнедеятельностью. Вход в нагруженные флуоресцентными зондами хлортетрациклин (ХТЦ) и Фура-2АМ клетки гранулезы коров различных соединений вызывает изменение концентрации цитоплазматического и запасенного во внутриклеточных депо кальция. В интактных нагруженных ХТЦ клетках гранулезы добавление пролактина (ПРЛ) стимулировало освобождение Са2 из внутриклеточных депо. В необработанных клетках гепарин не способен самостоятельно проникать в клетки. Для обеспечения входа гепарина в клетки используется процедура пермеабилизации, то есть клетки предварительно обрабатываются детергентом (дигитонином). Использование гепарина приводило к ингибированию освобождения Са2 из внутриклеточных депо, стимулированного добавлением ПРЛ. Обработка клеток детергентом дигитонином не оказывала влияния на стимулированное ПРЛ освобождение Са2 из депо и ингибирующее действие гепарина на выход Са2 из внутриклеточных депо. В интактных нагруженных Фура-2АМ клетках гранулезы добавление ПРЛ не приводило к увеличению концентрации цитоплазматического кальция.После обработки дигитонином нагруженных Фура-2АМ клеток гранулезы внесение ПРЛ приводило к увеличению концентрации цитоплазматического Са2, которое ингибировалось при добавлении гепарина. Полученные данные позволяют предположить, что ХТЦ образует поры на поверхности клеток гранулезы, способствуя таким образом проникновению в клетки различных соединений.In the absence of the necessary receptors on the cell membrane surface, the compounds are not able to penetrate into the cells. Various methods are used to ensure the entry of such compounds into the cells (permeabilization, compound injection into the cell, etc.), however, all these methods are expensive to use or have a negative effect on the cellular viability. The penetration of various compounds into the granulosa cells of cows treated with chlortetracycline (CTC) and Fura-2AM fluorescent probes causes a change in the concentration of cytoplasmic calcium and calcium stored in intracellular stores. In intact CTC-treated granulosa cells, the addition of prolactin (PRL) stimulated the Ca2 release from the intracellular stores. In untreated cells, heparin is not able to independently penetrate into the cells. To ensure the penetration of heparin into the cells, the permeabilization procedure when the cells are pre-treated with a detergent (digitonin). The usage of heparin led to the inhibition of Ca2 release from the intracellular stores stimulated by the PRL. The treatment of the cells with digitonin did not affect the PRL-stimulated release of Ca2 and the inhibitory effect of heparin on the Ca2 release from the stores. In intact Fura-2AM-treated granulosa cells, the addition of PRL did not increase the concentration of cytoplasmic calcium. After digitonin treatment of Fura-2AM-treated granulosa cells, the supplementation of PRL led to an increase in the concentration of cytoplasmic Ca2, which was inhibited by the heparin addition. The obtained data suggest that CTC forms pores in the membrane of granulosa cells facilitating the penetration of various compounds into cells.


1988 ◽  
Vol 8 (7) ◽  
pp. 2875-2883
Author(s):  
N Parkin ◽  
A Darveau ◽  
R Nicholson ◽  
N Sonenberg

We have previously shown that the 5' noncoding region of mouse c-myc mRNA has a negative effect on translational efficiency in a rabbit reticulocyte lysate (A. Darveau, J. Pelletier, and N. Sonenberg, Proc. Natl. Acad. Sci. USA 82:2315-2319, 1985). We wanted to localize and characterize the inhibitory translational element(s) in the mRNA and to study its effect in other in vitro and in vivo systems. Here we report that the restrictive element is confined to a 240-nucleotide sequence of the 5' noncoding region of mouse c-myc mRNA and that this sequence acts in cis to inhibit the translation of a heterologous mRNA. In addition, we report that the cis-inhibitory effect is also exhibited in microinjected Xenopus oocytes and wheat-germ extracts but not in HeLa cell extracts. Transfection of corresponding plasmid DNA constructs into several established cell lines did not produce the cis-inhibitory effect. A model to explain these results is presented.


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