Interactions between Plants and Epiphytic Bacteria Regarding Their Auxin Metabolism

Wichner, Siegfried; Libbert, Eike

doi:10.1111/j.1399-3054.1968.tb07275.x

Cited by 17 publications

(3 citation statements)

References 23 publications

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“…Corn roots were ground in distilled water without chloramphenicol (a procedure which does little damage to the bacteria [22]), '4C-MH was added, and the mixture was incubated for as long as 24 hr. If bacteria were present in great numbers and were playing a significant role in the binding of MH, on or in intact roots, they should be even more active in the homogenates.…”

Section: Resultsmentioning

confidence: 99%

“…To determine the rates of uptake and binding of 'IC in corn roots, the seedlings were incubated with their roots in aerated 14C-MH solution containing chloramphenicol to suppress bacterial growth (15,18,22). After thorough washing and excision, the roots (10 per sample) were used whole or cut into sections and ground at 40 in a mortar with a bit of sand and 2 drops of mercaptoethanol, 2 ml of 0.1% (w/w) sodium dodecyl sulfate in 0.01 M tris (pH 7.4), and 1 ml of H20-saturated phenol.…”

Section: Methodsmentioning

confidence: 99%

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Metabolism and Binding of ¹⁴C-Maleic Hydrazide

Noodén

1970

Plant Physiol.

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Maleic hydrazide (MH) is taken up by corn and pea seedling roots and bound to some material which is insoluble in 80% ethanol or 5% trichloroacetic acid. 14C-MH is stable metabolically; chromatography of the 80% ethanol-soluble 'IC from treated corn roots and tobacco pith gives no indication of degradation. Very little 14C-MH is bound in the zone of cell division (where MH acts to inhibit root elongation) or even in the region of cell enlargement in corn roots and most is bound 1 or more centimeters behind the tip. Likewise, very little MH is bound in corn coleoptile and tobacco pith sections. About 90% of 14C-MH bound in corn roots is associated with large particles which may be cell wall fragments. The binding is blocked by azide and dinitrophenol, indicating a requirement for metabolic energy; however, inhibitors of protein synthesis (chloramphenicol, puromycin, cycloheximide) and DNA synthesis (fluorodeoxyuridine) do not inhibit binding. Only very small amounts of MH are bound in root homogenates, providing further evidence that the binding process is active. Once the MH is bound in the roots, the complex is stable for at least 1 week. Treatment with 2-aminoethanol releases MH.Over the past 2 decades, maleic hydrazide has attracted a great deal of research effort by plant physiologists and cytologists because of its effects on development and chromosome structure; however, its mechanism of action is still unknown (8,16,24). Several years ago Callaghan and Grun (4) and Baker (2) reported that 14C-MH2 was bound selectively in the nuclei of root tips. Thus it appeared likely that a study on the binding of MH would shed some light on how it acts. This paper is concerned with the uptake of MH, its metabolic stability, and some of the characteristics of its binding to some unidentified macromolecule(s). A preliminary report of these findings has been made (14). MATERIALS AND METHODSSeeds of Zea mays Michigan 250 RF hybrid (a yellow field corn) were surface sterilized and germinated in vermiculite as described elsewhere (15). The corn coleoptile sections, tobacco pith explants, and pea seedlings (Pisum sativum variety Alaska)were also grown and prepared as before (15,16 14C-Maleic hydrazide with the label in the 1-position and a specific radioactivity of 4.12 mc/mmole was obtained from Tracerlab, Waltham, Mass. The radiochemical purity of all batches of '4C-MH was checked by descending chromatography using three solvent systems. These were n-butanol, concentrated acetic acid, H20 (6:1:2, v/v); i-propanol, concentrated ammonia, H20 (60:15:25, v/v); and 72% crystalline reagent phenol, 28% H20 (w/v). More than 99% of the 14C-MH was in the MH peak; no other peaks of radioactivity could be detected. In the three solvents used above the RFS of "4C-MH were 0.7 to 0.8.To determine the rates of uptake and binding of 'IC in corn roots, the seedlings were incubated with their roots in aerated 14C-MH solution containing chloramphenicol to suppress bacterial growth (15,18,22). After thorough washing and excision, the ro...

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Metabolism and Binding of ¹⁴C-Maleic Hydrazide

Noodén

1970

Plant Physiol.

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“…The existence of BIPs was recognized very early in the research on auxin, and plant-associated BIPs have long been considered a source of contamination in measurements of IAA present in plant tissues (24,51,52). Later, BIPs were identified as the cause of symptoms associated with severe plant diseases such as gypsophila gall (26), knot disease of olive and oleander (43), and russet of pear fruit (25), or, in other cases, as benefactors of plants, e.g., nitrogen-fixing Bradyrhizobium japonicum in root nodules (9) and plant-growth-promoting rhizobacteria such as Pseudomonas putida (33).…”

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Utilization of the Plant Hormone Indole-3-Acetic Acid for Growth by Pseudomonas putida Strain 1290

Leveau

Lindow

2005

Appl Environ Microbiol

274

146

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We have isolated from plant surfaces several bacteria with the ability to catabolize indole-3-acetic acid (IAA). One of them, isolate 1290, was able to utilize IAA as a sole source of carbon, nitrogen, and energy. The strain was identified by its 16S rRNA sequence as Pseudomonas putida. Activity of the enzyme catechol 1,2-dioxygenase was induced during growth on IAA, suggesting that catechol is an intermediate of the IAA catabolic pathway. This was in agreement with the observation that the oxygen uptake by IAA-grown P. putida 1290 cells was elevated in response to the addition of catechol. The inability of a catR mutant of P. putida 1290 to grow at the expense of IAA also suggests a central role for catechol as an intermediate in IAA metabolism. Besides being able to destroy IAA, strain 1290 was also capable of producing IAA in media supplemented with tryptophan. In root elongation assays, P. putida strain 1290 completely abolished the inhibitory effect of exogenous IAA on the elongation of radish roots. In fact, coinoculation of roots with P. putida 1290 and 1 mM concentration of IAA had a positive effect on root development. In coinoculation experiments on radish roots, strain 1290 was only partially able to alleviate the inhibitory effect of bacteria that in culture overproduce IAA. Our findings imply a biological role for strain 1290 as a sink or recycler of IAA in its association with plants and plant-associated bacteria.One intriguing type of interorganismal interaction is the manipulation by some microbes of their host's hormone system. A good example is given by bacteria of the genus Wolbachia, which convert male woodlice into females, supposedly by suppressing a gland that produces a masculinizing hormone (37). Another striking example is the microbial production of plant hormones such as auxin, cytokinin, and gibberellin, which allows certain bacteria and fungi to direct a plant's physiology toward their own advantage (5,7,14,20).Indole-3-acetic acid (IAA) is the main auxin in plants, controlling many important physiological processes including cell enlargement and division, tissue differentiation, and responses to light and gravity (45). Bacterial IAA producers (BIPs) have the potential to interfere with any of these processes by input of IAA into the plant's auxin pool. The consequence for the plant is usually a function of (i) the amount of IAA that is produced and (ii) the sensitivity of the plant tissue to changes in IAA concentration. A root, for instance, is one of the plant's organs that is most sensitive to fluctuations in IAA, and its response to increasing amounts of exogenous IAA extends from elongation of the primary root, formation of lateral and adventitious roots, to growth cessation (8).The existence of BIPs was recognized very early in the research on auxin, and plant-associated BIPs have long been considered a source of contamination in measurements of IAA present in plant tissues (24, 51, 52). Later, BIPs were identified as the cause of symptoms associated with severe plant disease...

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