| Soil salinizaion is one of the most serious problems which influence agricultural production and ecological environments. Alkaline soil, which contains excessive Na2CO3(sodium carbonate) and NaHCO3 (sodium bicarbonate), inhibits the rice growth and development, and futhermore limits the rise in rice yield. To solve this problem, one of the most economical and feasible approaches to exploit and utilize the alkaline soil is to breed for new rice varieties tolerant to alkaline. The methods of gene differential expression and gene cloning such as Northern blot analysis and cDNA-RAPD provide a new channel for unraveling the molecular mechanisms of rice adaptation to carbonate stress. Rice is moderately saline-tolerant crop, studies of the molecular mechanisms of rice adaptation to sodium carbonate and sodium bicarbonate stress, will guide the breeding of alkaline tolerant transgenic crops, therefore, japonica rice variety Nipponbare (Oryza sativa L.) was employed as materials, at first, under the stress condition of both different concentrations of NaCl, NaHCO3 and Na2CO3, and pH value, stress effects on the seed germination and seedlings growth were compared, and neutral red staining was also detected. Moreover, the transcription profiles of genes, such as CA, HSP90, PEPCase, NADP-MEl, NADP-ME2, PM-H+-ATPase, V-H+-ATPase, FB8(mitochondria ATPase 6kD subunit), FB24(APX), FB37 (thoredoxin) and FB38(UDPG-glucuronyl transferase), in root and shoot, were further comparatively analysed, cDNA-RAPD method was applied to clone the VB12-independent methionine synthetase gene(MetE) and ribosome protein large subunit 16 (rpL16). The main results were as follows:1. The different stress levels of H2O, NaCl, NaHCO3 and Na2CO3 in different pH values, affected seed germination and seedlings growth. Under pH5.00-8.50, seed germination rate was high. Rice root was more resistant to NaCl than the shoot, but more sensitive to carbonate stress than the shoot. The alkaline stress sensitivity of seedlings growth was in the order of Na2CO3 > NaHCO3> NaCl. Judging from dry root weight and dry shoot weight, stress threshold concentration was NaCl (160mmol.l-1, pH7.00), NaCl (140-160mmol.l-1, pH8.50), NaCl(120mmol.l-1, pH10.50), NaHCO3(60-80mmol.l-1, pH8.50), Na2CO3 (30mmol.l-1,pH 10.50).2. The different concentration levels of NaCl, NaHCO3 and Na2CO3 under different pHvalues slightly affected lOd old seedlings growth, the main performance was characterized by inhibition of seedlings growth in affecting the root and shoot growth, severity of root stress was more intense than that of shoot, sensitivity degree was in the order of Na2CO3> NaHCO3> NaCl, stress effect was increasingly obvious after 6d treatment.3. After 6d treatment of seedlings with NaCl, NaHCO3 and Na2CO3, neutral red staining of root tips cross section showed that, with the depth of stress level, acidification of root tips aggravated, the elongation zone was stained more deeply than maturation zone, main staining area was focused on sclerenchymatous tissue of exodermis, endodermis and pericycle, while cortical layer cells were slightly stained. Stainability was related with the metabolism activity and ion transport in the elongation zone.4. Characterization of gene transcription of time course in root and shoot during seedlings stage showed that, FB8 gene was more strongly expressed in NaHCO3 (60mmol.r-1,pH8.50) than that in H2O in 6h, after that, transcription would steadily increase, transcription of gene FB24 reached the peak in 48h after treatment, 3.05 times higher than that in E^O, transcription of gene FB38 was 2.41 times higher than that in H2O in 12h after treatments, the transcription of gene FB37 gradually reduced after different treatments of time course, gene PEPCase was weakly induced to transcribe, transcription of gene HSP90 in 48h increased by 2.48 times higher than in H2O, gene CA was more significantly reduced to transcribe than that in corresponding control, the transcription of gene V-lf-ATPase reduced more rapidl...
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