Effects of Soil Salinity on the Expression of Betaine Aldehyde Dehydrogenase in Leaves: Investigation of Hydraulic, Ionic and Biochemical Signals
Effects of Soil Salinity on the Expression of Betaine Aldehyde Dehydrogenase in Leaves: Investigation of Hydraulic, Ionic and Biochemical Signals
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土壤盐分对叶片甜菜碱醛脱氢酶表达的影响：水力、离子和生化信号的研究
DOI：
10.1071/pp9920555
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发表时间：
1992
期刊：
影响因子：
--
通讯作者：
A. Hanson
中科院分区：
文献类型：
--
作者：
K. McCue;A. Hanson
甜菜碱醛脱氢酶（BADH）是甜菜碱合成的最后一步。BADH酶和BADH mRNA的水平已经被证明在盐胁迫下增加了几倍。为了更彻底地表征这种诱导，我们分析了不同盐渍化制度下甜菜植株（Beta vulgaris L.）叶片中BADH mRNA水平和酶活性。盐冲击后（从0 ~ 400 mM NaCI）， BADH酶活性在数天内缓慢上升。相反，BADH mRNA水平在数小时内先下降后升高。盐碱化植株生根培养基浸出盐后，BADH酶活性下降，半衰期大于4天。然而，BADH mRNA水平急剧下降，表观半衰期为2 h，这表明BADH基因的转录或BADH mRNA在叶片中的稳定性可以对根周围盐度的变化做出非常动态的响应。在逐渐盐渍化后再处理不同NaCl浓度的植株中，酶的稳态水平在0 ~ 500 mM NaCl之间持续上升，而BADH mRNA的稳态水平在100 mM NaCl时达到平稳水平。总的来说，观察到的BADH mRNA波动不能令人满意地解释为对水力信号的响应。这表明非液压信号或来自根部的信号的参与。非水力信号不太可能是NaCl，因为暴露于盐浓度下的叶盘（典型的盐碱化叶片外质体）没有积累BADH mRNA。因此暗示了一个生化信使。虽然脱落酸在叶盘上的应用引起了BADH mRNA水平的显著增加，但这些水平比在完整的盐碱化植物叶片上观察到的要小几倍，这表明有其他物质的参与。
Betaine aldehyde dehydrogenase (BADH) catalyses the last step in glycine betaine synthesis. The levels of BADH enzyme and BADH mRNA have previously been shown to be increased several-fold by salt stress. To characterise this induction more thoroughly, BADH mRNA levels and enzyme activities were analysed in leaves of sugar beet plants (Beta vulgaris L.) subjected to different salinisation regimes. Following a salt shock (transfer from 0 to 400 mM NaCI) BADH enzyme activity rose slowly for several days. In contrast, BADH mRNA level first decreased for several hours, and then increased. When salt was leached from the rooting medium of salinised plants, BADH enzyme activity declined, with a half-life of more than 4 days. However, the level of BADH mRNA declined sharply with an apparent half-life of 2 h showing that transcription of the BADH gene or the stability of BADH mRNA in leaves can respond very dynamically to salinity changes around the root. In plants which had been gradually salinised and then held at various NaCl concentrations, the steady state level of enzyme rose continuously between 0 and 500 mM NaCl, whereas that of BADH mRNA reached a plateau at 100 mM NaCl. In general, the observed BADH mRNA fluctuations could not be satisfactorily explained by assuming them to be responses to hydraulic signals. This suggests the participation of a non-hydraulic signal or signals coming from the root. The non-hydraulic signal is unlikely to be NaCl, because leaf disks exposed to salt concentrations typical of the apoplast of salinised leaves did not accumulate BADH mRNA. A biochemical messenger is thus implied. Although abscisic acid application to leaf disks elicited significant increases in BADH mRNA level, these were several-fold smaller than those observed in leaves of intact salinised plants, suggesting the involvement of some other substance.