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

Abstract

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-

Hormone physiology of pea mutants prevented from flowering by mutations gi or veg1

“…The low level of GA 20 in compact gi and veg1 plants indicates that the pathway is blocked or down‐regulated prior to synthesis of GA 20 . A similar conclusion was reached by Davies et al (1986) and Halinska et al (1989) in relation to changes in GA levels during apical senescence in different reproductive lines of pea. However, GA metabolism may also be important.…”

Metabolism of Gibberellin A12 and A12-Aldehyde in Developing Seeds of Pisum sativum L.

“…When the same material was applied to pea shoots for 3 h, about 50 to 60% was metabolized to putative ['4C]GA53, GA44, GA19,. GA2,, and GA., (14). GA5,-aldehyde conjugate was also produced as a major peak, but it was no longer a dominant one as found in seed coat incubations (Fig.…”

The Control of Apical Bud Growth and Senescence by Auxin and Gibberellin in Genetic Lines of Peas

“…Our previous failure (Davies et al, 1982) to identify GA, by GC-MS in G2 pea shoots can probably be attributed to the much lower sensitivity of the GC-MS we used in that study. The increased level of GA,, and GA, in SD-grown G2 plants is probably the result of an overall increase in the metabolic flux through the early 13-hydroxylase pathway under short photoperiods, since SDgrown G2 peas produced more [14C]GA,,, GA,, GA19, and GA,, from applied [14C]GA,,-aldehyde than LD-grown plants (Davies et al, 1986a;Halinska et al, 1989). Thus photoperiod possibly operates at one of the two metabolic steps between GA,,-aldehyde and GA,,, although modulation at other points of GA, biosynthesis is not excluded.…”