J. Plant Physiol. 159. 671–674 (2002)  Urban & Fischer Verlag http://www.urbanfischer.de/journals/jpp Short Communication Propionate, a source of β-alanine, is an inhibitor of β-alanine methylation in Limonium latifolium , Plumbaginaceae Bala Rathinasabapathi* Horticultural Sciences Department, University of Florida, Gainesville, FL 32611-0690, USA Received November 9, 2001 · Accepted January 2, 2002 Summary The origin of β-alanine was investigated in Limonium latifolium (Plumbaginaceae), an angiosperm species that methylates β-alanine to β-alanine betaine, an osmoprotective compound. The hypothe- sis that propionate metabolism leads to β-alanine in L. latifolium was tested using radiotracer labeling techniques. 2-[ 14 C]-Propionate was supplied to leaf and root tissues. Following incubation for defined periods, radiolabel was identified in β-alanine. However, in both the tissues, little radioactivity was found in the methylated derivatives of β-alanine namely N-methyl β-alanine, N,N-dimethyl β-alanine and β-alanine betaine, suggesting that propionate was inhibitory to β-alanine methylation. This con- clusion was confirmed by in vitro assays wherein propionate was found to be highly inhibitory to β-alanine N-methyltransferase activity in a leaf protein fraction. Key words: β-alanine – β-alanine betaine – Limonium latifolium – propionate – radiotracer analysis Abbreviations: TLC = thin layer chromatography Introduction β-Alanine is a vital non-protein amino acid as one of the pre- cursors to pantothenic acid. In certain members of the stress- tolerant plant family Plumbaginaceae, it is methylated to β-alanine betaine, an osmoprotective compound suitable for saline and hypoxic conditions (Hanson et al. 1991). In some * E-mail corresponding author: brath@mail.ifas.ufl.edu legumes, β-alanine is a precursor to homoglutathione, a com- pound implicated in heavy metal detoxification (Klapheck 1988). Despite β-alanine’s central role in pantothenate pro- duction and secondary role in plant-environment interactions, its origin is not well understood in plants. For our biochemical investigations on β-alanine synthesis in plants, we employed Limonium latifolium (Plumbagina- ceae), since in this species a large flux of β-alanine is methyl- ated to β-alanine betaine via N-methyl β-alanine and N,N- 0176-1617/02/159/06-671 $ 15.00/0