Enzymatic characterization of peroxisomal and cytosolic betaine aldehyde dehydrogenases in barley

Betaine aldehyde dehydrogenase (BADH; EC 1.2.1.8) is an important enzyme that catalyzes the last step in the synthesis of glycine betaine, a compatible solute accumulated by many plants under various abiotic stresses. In barley ( Hordeum vulgare L.), we reported previously the existence of two BADH genes ( BBD1 and BBD2 ) and their corresponding proteins, peroxisomal BADH (BBD1) and cytosolic BADH (BBD2). To investigate their enzymatic properties, we expressed them in Escherichia coli and purified both proteins. Enzymatic analysis indicated that the affinity of BBD2 for betaine aldehyde was reasonable as other plant BADHs, but BBD1 showed extremely low affinity for betaine aldehyde with apparent K_m of 18.9 μ M and 19.9 m M , respectively. In addition, V_max/K_m with betaine aldehyde of BBD2 was about 2000-fold higher than that of BBD1, suggesting that BBD2 plays a main role in glycine betaine synthesis in barley plants. However, BBD1 catalyzed the oxidation of ω-aminoaldehydes such as 4-aminobutyraldehyde and 3-aminopropionaldehyde as efficiently as BBD2. We also found that both BBDs oxidized 4- N -trimethylaminobutyraldehyde and 3- N -trimethylaminopropionaldehyde.     

Abscisic acid is involved in the water stress-induced betaine accumulation in pear leaves

ABA exogenously applied to the leaves of the whole plants of pear (Pyrus bretschneideri Redh. cv. Suly grafted on Pyrus betulaefolia Rehd.) significantly increased the betaine concentrations in the leaves when the plants were well watered. The plants subjected to 'drought plus ABA' treatment had significantly higher betaine concentrations in their leaves than those given drought treatment alone. The 'drought plus ABA' treatment increased the amount of betaine aldehyde dehydrogenase (BADH, EC 1.2.1.8) and its activity in the leaves more than did the drought treatment alone. The experiments with detached leaves showed that ABA treatment significantly increased the concentration of betaine, activity of BADH and apparent amount of BADH in non-dehydrated leaves, and enhanced the accumulation of betaine, activity of BADH and apparent amount of BADH in dehydrated leaves. These effects of ABA were both time- and dose-dependent. Two ABA isomers, (-)-cis, trans-ABA and 2-trans, 4-trans-ABA, had no effect on the betaine accumulation in the leaves, showing that the ABA-induced effects are specific. These data demonstrate that ABA is involved in the drought-induced betaine accumulation in the pear leaves.     

高粱ATP合成酶E亚基基因(SbATPase-E)的克隆及其抗逆功能研究

高粱是一种抗旱性较强的禾谷类作物。本研究在高粱中克隆到一个全长为693 bp的编码ATP合成酶E亚基的基因(SbATPase-E)。在高粱幼苗期,SbATPase-E基因受Na Cl和脱落酸(ABA)处理诱导上调表达。该基因在拟南芥中过量表达可提高转基因植株的耐旱性和耐盐性,在逆境胁迫条件下转基因拟南芥植株较野生型植株根系发达,可能是转基因植株耐旱性和耐盐性提高的主要原因。在干旱胁迫条件下,转基因植株中DREB2A、P5CS1、RD29A、RAB18和ABI1基因的表达量相对于野生型植株中的表达量提高更为显著;在高盐处理条件下,转基因植株中SOS1和SOS2基因的表达量也较野生型植株中的表达量明显提高。这些抗逆相关基因的上调表达可能是转基因植株抗逆性提高的主要分子机制。     

Effect of salinity and abscisic acid on accumulation of glycinebetaine and betaine aldehyde dehydrogenase mRNA in Sorghum leaves (Sorghum bicolor)

The effects of salt stress and abscisic acid (ABA) on the expression of betaine aldehyde dehydrogenase (BADH) were determined in sorghum (Sorghum bicolor L.) plants. BADH mRNA expression was induced by salinity, and the timing coincided with the observed glycinebetaine (betaine) accumulation. The leaf water potential in the leaves of the sorghum plants was significantly affected by salinity. In response to salinity, betaine, ABA, Na and Cl accumulations increased 6-, 16-, 90-, and 3-fold, respectively. In the leaf disks from unsalinized plants incubated on NaCl, or ABA solution, the BADH mRNA level was lower than in the ABA-treated disks. Exogenous application of the ABA biosynthetic inhibitor fluridone to the NaCl-treated disks reduced the ABA accumulation and BADH mRNA levels compared with NaCl-treated leaves. The results indicate that the salt-induced accumulation of betaine and BADH mRNA coincides with the presence of ABA.