Preferential accumulation of betaine uncoupled to choline monooxygenase in young leaves of sugar beet--importance of long-distance translocation of betaine under normal and salt-stressed conditions.
It has been reported that glycinebetaine (betaine) is synthesized in response to abiotic stresses via a two-step oxidation of choline in which choline monooxygenase (CMO) and betaine aldehyde dehydrogenase (BADH) are involved. Here we show that significant amounts of betaine, > 20 micromol/gFW, accumulated in young leaves of Beta vulgaris even under normal growth conditions, whereas levels in old leaves, cotyledons, hypocotyls, and roots were low. Under the same conditions, CMO accumulates exclusively in old leaves and is difficult to be detected in young leaves. By contrast, the levels of BADH were high in all tissues. Exogenously supplied choline was converted into betaine in old leaves, but levels were significantly lower in young leaves under the same conditions. When d(11)-betaine was applied exogenously to old leaves, it was translocated preferentially into young leaves and roots. In response to salt stress, betaine levels increased in all tissues, but most significantly increased in young leaves. The levels of CMO increased in various tissues, but were low in young leaves. A betaine transporter gene was isolated. Its expression was more strongly induced in old leaves than in young leaves. Based on these data, we discussed the role of CMO and betaine transporter under stress and non-stress conditions.
Yamada
Nana
N
Graduate School of Environmental and Human Sciences, Meijo University, Nagoya 468-8502, Japan.
Promden
Worrawat
W
Yamane
Koji
K
Tamagake
Hideto
H
Hibino
Takashi
T
Tanaka
Yoshito
Y
Takabe
Teruhiro
T
D027461:Beta vulgaris / Q000235:genetics / Q000378:metabolism*; D001622:Betaine / Q000378:metabolism*; D050728:Betaine-Aldehyde Dehydrogenase / Q000378:metabolism; D050260:Carbohydrate Metabolism; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D050485:GABA Plasma Membrane Transport Proteins; D009994:Osmolar Concentration; D010105:Oxygenases / Q000378:metabolism*; D018515:Plant Leaves / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D012965:Sodium Chloride / Q000378:metabolism; D013312:Stress, Physiological
D002352:Carrier Proteins; D050485:GABA Plasma Membrane Transport Proteins; C072207:betaine plasma membrane transport proteins; D001622:Betaine; D012965:Sodium Chloride; D012964:Sodium; C105448:choline monooxygenase; D010105:Oxygenases; D050728:Betaine-Aldehyde Dehydrogenase; D011188:Potassium