Photoperiod Modification of [ 14 C]Gibberellin A 12 Aldehyde Metabolism in Shoots of Pea, Line G2

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To interpret the metabolism of radiolabeled gibberellins A12-aldehyde and A12 in shoots of pea (Pisum sativum L.), the identity of the radiolabeled peaks has to be determined and the endogenous presence of the gibberellins demonstrated. High specific activity [14C]GA12 and [14C]GA12-aldehyde were synthesized using a pumpkin endosperm enzyme preparation, and purified by high performance liquid chromatography (HPLC).[14C]GA12 was supplied to upper shoots of pea, line G2, to produce radiolabeled metabolites on the 13-OH pathway. Endogenous compounds copurifying with the [14C]GAs on HPLC were analyzed by gas chromatography-mass spectrometry. The endogenous presence of GAN, GA", GA19 and GA20 was demonstrated and their HPLC peak identity ascertained. The 14C was progressively diluted in GAs further down the pathway, proportional to the levels found in the tissue and inversely proportional to the speed of metabolism, ranging from 63% in GAN to 4% in GA20. Calculated levels of GA2o, GA19, GA.", and GAN, were 42, 8, 10, and 0.5 nanograms/ gram, respectively.The identification of endogenous gibberellins provides the necessary starting point from which metabolism and physiological studies can begin. The endogenous GAs of pea seeds and shoots have been extensively studied but evidence for some metabolic steps in vivo is still lacking (7,14). In the G2 genetic line of.neas (Pisum sativum L.) growth is indeterminate in short photoperiods while in long photoperiods the senescence of the plants takes place (12). Indeterminate growth is correlated with a higher level of biologically active GAs (13) which were subsequently associated with GAs identified by GC-MS as GA20 and GA,9 (5). In addition, the presence of GA29 and GA29-catabolite was shown in shoot extracts (5). When ['4C]GA,2-aldehyde is metabolized by G2 pea shoots many products are formed (4). The levels of the 14C metabolites tentatively identified as GA53, GA44, GA19, and GA20 were higher in shoots grown in SD than in those grown in LD. Since the products of ['4C]GA,2-aldehyde were tentatively identified from the HPLC retention time of en-

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confidence: 82%

Section: Gc-ms Analysismentioning

confidence: 99%

Further Identification of Endogenous Gibberellins in the Shoots of Pea, Line G2

Halinska¹,

Davies²,

Lee³

et al. 1989

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“…1). We estimated the amount of GA53 present in the composite extract of pea fruits based on two assumptions: (1) that pea seeds of this age contain approximately 8 Ag of GA20/seed (10); and (2) that equal amounts of GA53 and GA20 generate equivalent TIC traces. After accounting for recovery, the amount of GA53 present in the composite extract was estimated from the appropriate TIC traces of peak J (22 DAF) and peak G (composite) to be 0.7 Ag/g fwt.…”

Section: Discussionmentioning

confidence: 99%

“…Peak G represented most of the radioactivity recovered in the 0.5 h samples but decreased thereafter to 1.2% after 24 h (Table II). Usually, peaks I and J co-eluted on HPLC system 1 at 16.8 min although some separation could be achieved on a superior column (8). Peaks I and J were completely resolved on HPLC system 2.…”

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confidence: 99%

Identification of Pea Gibberellins by Studying [¹⁴C]GA₁₂-Aldehyde Metabolism

Maki

Brenner²,

Birnberg³

et al. 1986

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Experiments were designed to test the hypothesis that the labeled products recovered from plant tissue incubated with '4"CGA1r7-aldehyde (['4CGA12ald) would serve as appropriate I'Cimarkers for the recovery of naturally-occurring gibberellins (GAs). The I'CIGA12Ald (about 200 millicuries per millimole) was synthesized from pumpkin endosperm using 14,5-ClCmevalonic acid. It was added to the adaxial surface of isolated pea cotyledons at 22 days after flowering. Products recovered after 0.5 and 4.0 hour incubations yielded four major peaks which were separated by high perfornumce liquid chromatography (HPLC). These products were purified by multiple-column HPLC using on-line radioactivity detection. They were then added as I'4C1markers to two unlabeled pea extracts. In general, preparative HPLC followed by further HPLC purification resulted in a single UV-absorbing peak co-eluting with each 114Cimarker. These '4"C and UV-absorbing peaks were shown to contain GAI3, GA4, GA2, GA,, and GA17 by GC-MS. The fmding of GAS3 is novel; all others have previously been found in pea. Endogenous GAs of pea were thus readily detected using ['4CjGA,2ald metabolites as I'4Cimarkers to recover naturally occurring GAs suggesting that the method may be applicable in detecting naturally occurring GAs in other species.

“…The relative sink strength of pea plants may be regulated, at least in part, by the gibberellin content of the shoot (5).…”

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confidence: 99%

Photoperiodic and Genetic Control of Carbon Partitioning in Peas and Its Relationship to Apical Senescence

Kelly¹,

Davies²

1988

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Apical senescence but not flower initiation is delayed by short days (SD) compared to long days (LD) in pea plants (Pisum sativum L.) of genotype E Sn Hr. We recently reported that delay of senescence correlated with slower reproductive development, suggesting that fruits are weaker sinks for assimilates under delayed senescence conditions. Thus, we have examined assimilate partitioning in peas to determine if genotype and photoperiod regulate relative sink strength. Assimilate diversion by developing fruit has been implicated in senescence induction. A greater percentage of leaf-exported 14C was transported to fruits and a smaller percentage to the apical bud of G2 peas (genotype E S.4 Hr) in LD than in SD. Relatively more of the 14C delivered to the apical bud of G2 peas was transported to flower buds than to young leaves in LD as compared to SD.