Members of the Chenopodiaceae can accumulate high levels (>100 mol·(g DW)
-1) of glycine betaine (betaine) in leaves when salinized. Chenopodiaceae synthesize betaine by a two-step oxidation of choline (cholinebetaine aldehyde betaine), with the second step catalyzed by betaine aldehyde dehydrogenase (BADH, EC 1.2.1.8). High betaine levels have also been reported in leaves of species from several distantly-related families of dicotyledons, raising the question of whether the same betaine-synthesis pathway is used in all cases.Fast atom bombardment mass spectrometry showed that betaine levels of >100 mol·(g DW)
-1 are present in
Lycium ferocissimum Miers (Solanaceae),
Helianthus annuus L. (Asteraceae),
Convolvulus arvensis L. (Convolvulaceae), and
Amaranthus caudatus L. (Amaranthaceae), that salinization promotes betaine accumulation in these plants, and that they can convert supplied choline to betaine aldehyde and betaine.
Nicotiana tabacum L. and
Lycopersicon lycopersicum (L.) Karst. ex Farw. (Solanaceae),
Lactuca sativa L. (Asteraceae) and
Ipomoea purpurea L. (Convolvulaceae) also contained betaine, but at a low level (0.1–0.5 mol·(g DW)
-1. Betaine aldehyde dehydrogenase activity assays, immunotitration and immunoblotting demonstrated that the betaine-accumulating species have a BADH enzyme recognized by antibodies raised against BADH from
Spinacia oleracea L. (Chenopodiaceae), and that the M
r of the BADH monomer is in all cases close to 63 000. These data indicate that the cholinebetaine aldehydebetaine pathway may have evolved by vertical descent from an early angiosperm ancestor, and might be widespread (albeit not always strongly expressed) among flowering plants. Consistent with these suggestions,
Magnolia x soulangiana was found to have a low level of betaine, and to express a protein of M
r 63 000 which cross-reacted with antibodies to BADH from
Spinacia oleracea.Abbreviations BADH
Betaine aldehyde dehydrogenase
- DCIMS
desorption chemical ionization mass spectrometry
- FABMS
fast atom bombardment mass spectrometry
- M
r
relative molecular mass
- PAGE
polyacrylamide gel electrophoresis
- SDS
sodium dodecyl sulfate
- TLC
thin-layer chromatography
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