Chattopadhyay M K, Gupta S, Sengupta D N, Ghosh B
Department of Botany, Bose Institute, Calcutta, India.
Plant Mol Biol. 1997 Jun;34(3):477-83. doi: 10.1023/a:1005802320672.
The effect of salinity stress on the activity of arginine decarboxylase (ADC, EC 4.1.1.19), the first enzyme in biosynthesis of polyamines (PA) from arginine, as well as its transcript level has been compared in salt-sensitive (M-1-48) and salt-tolerant (Pokkali) rice cultivars. Treatment of 72 h grown seedlings either with increasing concentrations of NaCl or with 150 mM NaCl for different time periods, showed a gradual increase of activity in Pokkali. In M-1-48 an immediate increase followed by sharp decrease was observed on prolonged treatment beyond 6 h or above 150 mM NaCl. To generate a DNA probe for ADC, the polymerase chain reaction was used with oat genomic DNA and sequence-specific primers. A region of oat genomic DNA containing a coding sequence for 166 amino acids of the C-terminal part of the ADC enzyme was amplified and called OAD1. Southern analysis of EcoRI- or BamHI-cut genomic DNAs from different cultivars of rice with OAD1 as the probe revealed strong hybridization with one DNA fragment of rice and restriction fragment length polymorphism (RFLP) was noticed. Northern analysis of total RNA of rice with OAD1 as the probe revealed hybridization with a transcript of similar size to the ADC transcript in oat. While in Pokkali, at least a 20-fold accumulation of OAD1 homologous transcript was detected after treatment with 200 mM NaCl, only a seven-fold increase in transcript level was found in M-1-48 after 150 mM NaCl treatment. Results suggest that in the salt-tolerant rice cultivar Pokkali, ADC enzyme activity increases and its transcript also accumulates during the prolonged salinity stress, this mechanism is absent in the salt-sensitive rice cultivar M-1-48 where a prolonged period of salinity stress down-regulates both ADC activity and its transcript level.
在盐敏感型（M-1-48）和耐盐型（Pokkali）水稻品种中，比较了盐胁迫对精氨酸脱羧酶（ADC，EC 4.1.1.19）活性及其转录水平的影响。精氨酸脱羧酶是从精氨酸生物合成多胺（PA）的首个酶。用浓度递增的氯化钠处理生长72小时的幼苗，或用150 mM氯化钠处理不同时间段，结果显示Pokkali中该酶的活性逐渐增加。在M-1-48中，延长处理超过6小时或氯化钠浓度高于150 mM时，会立即出现活性增加，随后急剧下降。为了生成用于ADC的DNA探针，使用燕麦基因组DNA和序列特异性引物进行聚合酶链反应。扩增出燕麦基因组DNA中包含ADC酶C末端部分166个氨基酸编码序列的区域，称为OAD1。以OAD1为探针，对不同水稻品种经EcoRI或BamHI酶切的基因组DNA进行Southern分析，结果显示与水稻的一个DNA片段有强烈杂交，并观察到限制性片段长度多态性（RFLP）。以OAD1为探针，对水稻总RNA进行Northern分析，结果显示与燕麦中大小与ADC转录本相似的转录本发生杂交。在Pokkali中，用200 mM氯化钠处理后，检测到OAD1同源转录本至少积累了20倍；而在M-1-48中，用150 mM氯化钠处理后，转录本水平仅增加了7倍。结果表明，在耐盐水稻品种Pokkali中经过长时间盐胁迫后，ADC酶活性增加且其转录本也会积累，而在盐敏感水稻品种M-1-48中不存在这种机制，长时间的盐胁迫会下调ADC活性及其转录本水平。
