Effect of inhibition of phenylalanine ammonia‐lyase activity on growth of alfalfa cell suspension culture: Alterations in mitotic index, ethylene production, and contents of phenolics, cytokinins and polyamines

Abstract

The effect of inhibition of phenylpropanoid biosynthesis on the growth of Medicago sativa L. suspension culture was studied. 2‐Aminoindan‐2‐phosphonic acid (AIP), a potent inhibitor of phenylalanine ammonia‐lyase (PAL; EC 4.3.1.5), caused a marked reduction in the amount of hydroxycinnamic acid derivatives in a few hours after cell inoculation into AIP medium. The treatment of alfalfa suspension culture with this inhibitor increased the extractable PAL activity and elevated ethylene production during the growth cycle. The addition of AIP (10 μM) stimulated cell division activity during the growth cycle, although the onset of cell division was slightly delayed. The maxima of cytokinin content as well as of the mitotic index were postponed in AIP‐treated cells, however, the unchanged content of cytokinins did not correlate with increased mitotic activity of treated cells. The decreased level of hydroxycinnamic acid derivatives, which represent the phenolic conjugation partners of free polyamines (PAs), influenced the rate of PA conjugation. Consequently, the balance between free and conjugated PAs was shifted in favor of the free PA form. A potential role of the reduction of the pool of phenolic acids in the enhancement of cell division of alfalfa cell suspension culture is discussed.

Influence of auxins on somatic embryogenesis and alkaloid accumulation in Leucojum aestivum callus

“…The mechanism of action of phenolics is difficult to explain and somewhat ambiguous; however, it is supposed that they are one factor involved in determining the capacity of plant tissues to regenerate [42]. On the basis of our observations, the induction of Leucojum aestivum somatic embryos may also be connected to the presence of phenolic compounds in the callus.…”

“…Beruto et al [43] also observed a higher level of phenols in nonregenerating callus of Ranunculus asiaticus compared to regenerating callus. However, Hrubcová et al [41] and Cvirková et al [42] showed that nonembryogenic suspension of Medicago sativa produced more phenolic compounds than embryogenic suspension.…”

Regulation by Polyamines of Ornithine Decarboxylase Activity and Cell Division in the Unicellular Green Alga Chlamydomonas reinhardtii

“…The control of ODC degradation by the intracellular polyamine level and the antizyme level (Murakami and Hayashi, 1985;Hayashi and Murakami, 1995;Hayashi et al, 1996) is proposed to assure homeostatic regulation of both the ODC activity and the polyamine concentrations in mammalian cells. However, elevated polyamine levels have been found in proliferating plant and mammalian cells as well as in cancer cells (Hibshoosh et al, 1991;Auvinen et al, 1992;Moshier et al, 1993;Daoudi and Biondi, 1995;Marton and Pegg, 1995;Ben Hayyim et al, 1996;Fowler et al, 1996;Cvikrova et al, 1999). A rapid increase in ODC activity was measured when growth-arrested mammalian or plant cells were transferred to fresh culture medium enabling cell proliferation (Manzella et al, 1991;Fowler et al, 1996;Graff et al, 1997).…”

Role of Polyamines in Efficiency of Norway Spruce (Hurst Ecotype) Somatic Embryogenesis

“…The formation of somatic embryos in tissue cultures of wild carrot seemed to be also associated with high Spd level and much more Spd than Put was found in torpedo stage of these embryos (Mengoli et al, 1989). Especially Spd was implicated in somatic embryogenesis in tissue cultures of Vigna aconitifolia (Kaur-Sawhney et al, 1985), Hevea brasiliensis (El Hadrami & D'Auzac, 1992) and in the development of globular pro-embryos in alfalfa (Cvikrová et al, 1999). However, it is not always Spd, which is the dominant polyamine in somatic embryos of conifers.…”