Relation of Polyamine Biosynthesis to the Initiation of Sprouting in Potato Tubers

Abstract

The polyamines putrescine, spermidine, and spermine and their biosynthetic enzymes arginine decarboxylase, ornithine decarboxylase and Sadenosyl-L-methionine decarboxylase are present in all parts of dormant potato (Solamm tuberosum L.) tubers. They are equally distributed among the buds of apical and lateral regions and in nonbud tissues. However, the breaking of dormancy and initiation of sprouting in the apical bud region are accompanied by a rapid increase in ornithine decarboxylase and Sadenosyl-L-methionine decarboxylase activities, as well as by higher levels of putrescine, spermidine, and spermine in the apical buds. In contrast, the polyamine biosynthetic enzyme activities and titer remain practically unchanged in the dormant lateral buds and in the nonbud tissues. The rapid rise in ornithine decarboxylase, but not arginine decarboxylase activity, with initiation of sprouting suggests that ornithine decarboxylase is the rate-limiting enzyme in polyamine biosynthesis. The low level of polyamine synthesis during dormancy and its dramatic increase in buds in the apical region at break of dormancy suggest that polyamine synthesis is linked to sprouting, perhaps causally.The PA,2 Put, Spd, and Spm are present throughout the microbial, animal, and plant worlds (3, 7). In microbial and plant cells, Put is derived either from arginine via ADC and the intermediate Agm, or from ornithine by ODC. In mammalian cells, Put synthesis occurs only by the latter pathway. The Put thus formed is converted successively to Spd and Spm through propylamino group transfer from SAM mediated by SAMDC in all the above types of cells (3, 11). These amines have been implicated in several important processes involved in-cell growth and development, especially those involving nucleic acids (3,7,11,27 (2,10,14,15). PA appear to inhibit senescence by preventing Chl, protein, and RNA breakdown in leaves (16) and by increasing macromolecular synthesis and mitotic activity in protoplasts (15). The antisenescence properties of PA and their correlation with cell proliferation and differentiation lend support to the contention that they act as growth factors (3,5,11). Despite these observations, the relative roles of individual PA biosynthetic enzymes in dormant and actively dividing plant tissues is not well understood. We have, therefore, examined the activities of ADC, ODC, and SAMDC and the endogenous levels of Put, Spd, and Spm in dormant and actively growing tissues of potato tubers.MATERIALS AND METHODS Plant Materials. Idaho Russet baking potatoes (Solanum tuberosum L.) (U.S. No. 1) were purchased from the local supermarket. The tubers were firm, with no sign of sprouting, and were therefore regarded as dormant. Medium-size tubers were selected and allowed to sprout by storing them in the dark at room temperature for about 2 months. Samples of tissue were taken from dormant, initial, and advanced (profuse) sprouted tubers. Three areas from the same tuber showing different sprouting activity were selected for sampling ( Fig. 1...

Improved Method for HPLC Analysis of Polyamines, Agmatine and Aromatic Monoamines in Plant Tissue

“…Misidentification of the Agm peak in the original report (3) may require reevaluation of some data presented in later studies employing this HPLC method (4,8). For example, Kaur-Sawhney et al (8) reported a nearly fivefold increase in Agm titers of apical bud tissues of potato tubers during sprouting, although ADC activity in these tissues did not increase.…”

“…For example, Kaur-Sawhney et al (8) reported a nearly fivefold increase in Agm titers of apical bud tissues of potato tubers during sprouting, although ADC activity in these tissues did not increase. However, a fivefold increase in ODC activity was observed to accompany markedly elevated PA levels in these tissues.…”

Partial Purification and Characterization of Arginine Decarboxylase from Avocado Fruit, A Thermostable Enzyme

“…Arginine is converted by ADC2 to agmatine which is then converted to putrescine (1,11,12). In recent studies by Heimer et al (10) and Cohen et al (6) on tomato ovaries and fruits, it was observed that the activity of ODC changed during fruit development, whereas the relatively low '…”

Poliaminas na embriogênese somática em cenoura (Daucus carota L.)

“…Assim sendo, elevados níveis de poliaminas são necessários durante a embriogênese de cenoura em cultura de tecidos (FEIRER, et al, 1984). Os níveis de poliaminas livres e conjugadas aumentaram drasticamente durante a diferenciação e regeneração de plantas derivadas do mesofilo de Vigna em cultura deprotoplastos (KAUR-SAWHNEY et al, 1982). A formação de novas células está correlacionada com o aumento na síntese de DNA, RNA, proteínas e com a formação de poliaminas (COHEN et al, 1982).…”