Biosynthesis

Heller, Werner; Forkmann, G.

doi:10.1007/978-1-4899-2913-6_11

Cited by 132 publications

(52 citation statements)

References 203 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…At times when maximum root nodule initiation is required, the plant may convert most 2',4,4'-trihydroxychalcone to the strong nod inducer, 4,4'-dihydroxy-2'-methoxychalcone. Then if nod induction must be decreased, the plant could reduce the availability of 4,4'-dihydroxy-2'-methoxychalcone by using chalcone isomerase to produce the weak nod inducer 4',7-dihydroxyflavanone from 2',4,4'-trihydroxychalcone (12). This reaction also occurs spontaneously in the absence ofenzymatic factors.…”

Section: Discussionmentioning

confidence: 99%

A Chalcone and Two Related Flavonoids Released from Alfalfa Roots Induce nod Genes of Rhizobium meliloti

Maxwell¹,

Hartwig²,

Joseph³

et al. 1989

Plant Physiol.

221

167

View full text Add to dashboard Cite

Flavonoid signals from alfalfa (Medicago sativa L.) induce transcription of nodulation (nod) genes in Rhizobium melioti. Previous investigations identified the flavone luteolin as an active inducer in alfalfa seed extracts, but the nature of nod inducers released from roots has not been reported. Root exudate from 3-day-old alfalfa seedlings was purified and then assayed for biological activity with a nodABC-IacZ fusion in R. meliloti. Indentities of major nod inducers were established by spectroscopic analyses (ultraviolet/visible, proton nuclear magnetic resonance, and mass spectroscopy) and comparison with authentic standards. Major nod inducers, which were identified as 4',7-dihydroxyflavone, 4'-7-dihydroxyflavanone, and 4,4'-dihydroxy-2'-methoxychalcone, were released from seedling roots at 54, 22, and 20 picomole.plantr'. day-1, respectively. Luteolin was not found in these root exudates. The 4,4'-dihydroxy-2'-methoxychalcone induced nod genes at a concentration one order of magnitude lower than luteolin and is the first naturally released chalcone reported to have this function. Moderate and weak nod-inducing activity was associated, respectively, with 4',7-dihydroxyflavone and 4',7-dihydroxyflavanone.Alfalfa (Medicago sativa L.), an important leguminous forage crop throughout the world, forms N2-fixing root nodules in association with the soil bacterium Rhizobium meliloti. The earliest events of alfalfa nodule formation require expression ofthe nodulation (nod) DABC genes on the megaplasmid (pSym) of R. meliloti (8,16). Transcription of nodABC is induced through the cooperative action of the constitutive nodD product and components of root and seed exudates (22). Luteolin, 3',4',5,7-tetrahydroxyflavone, was isolated from alfalfa seed extracts and shown to participate in nod induction (23) evidence that some N2-dependent alfalfa seedlings are initially N-limited due to insufficient root nodule formation (10) and suggests that more nodules might be formed if more rhizobial cells are induced to initiate the infection process.The presence of active nod inducers in plants does not guarantee release into the rhizosphere. Yelton et al. (30) observed that extracts from some plants induced nod transcription in R. meliloti even when exudates ofthe same plants did not. In contrast, both extracts and exudates of alfalfa induced nod genes, but it is unclear if luteolin was solely responsible for nod induction.In order to better understand the process of nod-inducer release, it is necessary to identify active compounds actually exuded into the rhizosphere. The purpose ofthis study was to identify, quantify, and characterize the major nod inducers exuded by roots of young, unnodulated alfalfa seedlings. MATERIALS AND METHODS Plant CultureOne g of alfalfa (Medicago sativa L.) seed (cv 'Moapa 69') containing about 400 seeds (94% viable) was scarified, surfacesterilized 3 min with 70% ethanol, rinsed with sterile water, and imbibed in sterile, aerated water. Imbibing solutions were changed after 4 and 8 h to rem...

show abstract

Section: Discussionmentioning

confidence: 99%

A Chalcone and Two Related Flavonoids Released from Alfalfa Roots Induce nod Genes of Rhizobium meliloti

Maxwell¹,

Hartwig²,

Joseph³

et al. 1989

Plant Physiol.

221

167

View full text Add to dashboard Cite

show abstract

“…Phenylalanine enters the flavonoid biosynthetic pathway several steps before commitment to flavonoid biosynthesis (10). As a result, neither flavonoids that were present before treatment with 14C nor alternative molecular structures which originated from them would be labeled.…”

Section: Discussionmentioning

confidence: 99%

“…Such synthesis presumably would require active phenylpropanoid metabolism, including PAL2 activity, to supply carbon skeletons for general flavonoid formation (10). Newly synthesized flavonoids could be released directly into the rhizosphere or conjugated and stored in vacuoles.…”

mentioning

confidence: 99%

Concurrent Synthesis and Release of nod-Gene-Inducing Flavonoids from Alfalfa Roots

Maxwell

Phillips

1990

Plant Physiol.

View full text Add to dashboard Cite

Flavonoid signals from alfalfa (Medicago sativa L.) induce transcription of nodulation (nod) genes in Rhizobium meliloti. Alfalfa roots release three major nod-gene inducers: 4',7-dihydroxyflavanone, 4',7-dihydroxyflavone, and 4,4'-dihydroxy-2'-methoxychalcone. The objective of the present study was to define temporal relationships between synthesis and exudation for those flavonoids. Requirements for concurrent flavonoid biosynthesis were assessed by treating roots of intact alfalfa seedlings with [U-14C]-L-phenylalanine in the presence or absence of the phenylalanine ammonia-lyase inhibitor L-2-aminoxy-3-phenylpropionic acid (AOPP). In the absence of AOPP, each of the three flavonoids in exudates contained 14C. In the presence of AOPP, 14C labeling and release of all the exuded nod-gene inducers were reduced significantly. AOPP inhibited labeling and release of the strongest nod-gene inducer, methoxychalcone, by more than 90%. Experiments with excised cotyledons, hypocotyls, and roots incubated in solution showed that the flavonoids could be synthesized in and released from each organ. However, the ratio of the three flavonoids in exudates from intact plants was most similar to the ratio recently synthesized and released from excised roots. A portion of recentiy synthesized flavonoid aglycones was found conjugated, presumably as glycosides, in root extracts and may have been involved in the release process. Data from root extracts showed that formononetin, an isoflavonoid which does not induce nod genes, was present in conjugated and aglycone forms but was not released by normal intact roots. In contrast, roots stressed with CuCI2 did release the aglycone formononetin. Thus, the release process responsible for exudation of nod-gene inducers appears to be specific rather than a general phenomenon such as a sloughing off of cells during root growth. The synthesis and specific concurrent release of flavonoid nod-gene inducers in this study is consistent with the physiological requirement for nodule formation of the 3-day-old seedlings used.Alfalfa (Medicago sativa L.), an important leguminous forage crop, forms N2-fixing root nodules in association with the soil bacterium Rhizobium meliloti. Early events of alfalfa nodule formation require expression of nodulation genes including nodDABC on the megaplasmid of R. meliloti (6,15). Transcription of nodABC is induced through the cooperative action of the protein product of the nodD gene and components of root and seed exudates (21). Luteolin, '

show abstract

“…The fact that Me-J influences the secondary metabolism of plants is already established and reported (Ali et al 2007). Generally, phenolics and flavonoids are anti-oxidative in nature and are produced in the phenyl-propanoid pathway (Heller and Forkmann 1988;Lister et al 1996). Biosynthesis of phenolics and flavonoids in plants initiates through the deamination of L-phenylalanine to trans-cinnamic acid and ammonia by a strategic enzyme phenylalanine ammonia-lyase (PAL).…”

Section: Elicitation Of Adventitious Roots In Liquid Mediummentioning

confidence: 99%

Impacts of methyl jasmonate and phenyl acetic acid on biomass accumulation and antioxidant potential in adventitious roots of Ajuga bracteosa Wall ex Benth., a high valued endangered medicinal plant

Saeed

Ali

Khan

et al. 2017

Physiol Mol Biol Plants

View full text Add to dashboard Cite

Ajuga bracteosa is a medicinally important plant globally used in the folk medicine against many serious ailments. In the present study, effects of two significant elicitors, methyl jasmonate (Me-J) and phenyl acetic acid (PAA) were studied on growth parameters, secondary metabolites production, and antioxidant potential in adventitious root suspension cultures of A. bracteosa. The results showed a substantial increase in biomass accumulation, exhibiting longer log phases of cultures growth in response to elicitor treatments, in comparison to control. Maximum dry biomass formation (8.88 DW g/L) was recorded on 32nd day in log phase of culture when 0.6 mg/L Me-J was applied; however, PAA at 1.2 mg/L produced maximum biomass (8.24 DW g/L) on day 40 of culture. Furthermore, we observed the elicitors-induced enhancement in phenolic content (total phenolic content), flavonoid content (total flavonoid content) and antioxidant activity (free radical scavenging activity) in root suspension cultures of A. bracteosa. Application of 0.6 mg/L and 1.2 mg/L of Me-J, root cultures accumulated higher TPC levels (3.6 mg GAE/g DW) and (3.7 mg GAE/g DW) in the log phase and stationary phase, respectively, while 2.5 mg/L Me-J produced lower levels (1.4 mg GAE/g DW) in stationary phase of growth stages. Moreover, TFC and FRSA values were found in correspondence to TPC values in the respective growth phases at the similar elicitor treatment. Thus, a feasible protocol for establishment of adventitious roots in A. bracteosa was developed and enhancement in biomass and metabolite content in adventitious root was promoted through elicitation.

show abstract

Biosynthesis

Cited by 132 publications

References 203 publications

A Chalcone and Two Related Flavonoids Released from Alfalfa Roots Induce nod Genes of Rhizobium meliloti

A Chalcone and Two Related Flavonoids Released from Alfalfa Roots Induce nod Genes of Rhizobium meliloti

Concurrent Synthesis and Release of nod-Gene-Inducing Flavonoids from Alfalfa Roots

Impacts of methyl jasmonate and phenyl acetic acid on biomass accumulation and antioxidant potential in adventitious roots of Ajuga bracteosa Wall ex Benth., a high valued endangered medicinal plant

Contact Info

Product

Resources

About