The roles of phosphorus (P) starvation on the induction of intracellular acid phosphatase (ACP; EC 3.1.3.2) activity have been studied in a marine macroalga Ulva lactuca L. In comparison to creasy and dark green appearance in P-sufficient thalli (100 mM NaH2PO4), P-starved thalli (1 mM NaH2PO4) showed less crease and light green appearance. On exposure to 1 mM NaH2PO4, the growth rate, the contents of SRP, PP and P, and tissue C:P and N:P molar ratio decreased at day 3 and the contents of SNRP, TSP and polyphosphate decreased immediately. Intracellular ACP activity increased at day 3 after exposure to 1 mM NaH2PO4 and reached 16 folds of P-sufficient thalli at day 14, while extracellular alkaline phosphatase (AP; EC 3.1.3.1) activity increased at day 2 and reached the plateau after 4 days. Activity staining both on Native PAGE and IEF gel showed the induction of 10 and 9 ACP isoenzymes, respectively. Changes in intracellular ACP and extracellular AP activities were negatively correlated with SRP, SNRP, PP and P contents. After transferred to 100 mM NaH2PO4, the growth rate of 10 day-starvated thalli recovered after 5 days, the contents of SRP¡BSNRP¡BTSP and P, and the C:P and N:P molar ratio recovered to the level of P-sufficient thalli at day 1. When recovered to 100 mM NaH2PO4, extracellular AP activity of 10 day-starvated thalli decreased at day 2 and reached the minimum after day 8, while intracellular ACP activity decreased at day 3 and reached the minimum after day 8. The analog of Pi, Phi (1 mM) inhibited the intracellular ACP and extracellular AP activities induced by P swtarvation. The results of present investigation show that ACP has a role in the enhancement of P availability in U. lactuca via the enzymatically degradation of polyphosphates and organic P when suffers P deficiency.

Nutrients and cations have significant effect on activated sludge characteristics and therefore effect the efficiency of whole processes. To determine the properties in phosphorus deficient medium and the effect of calcium ions two reactor sets with two different phosphorus concentration (C/N/P=100/5/0.05 and C/N/P=100/5/1), three different concentrations of calcium (0.5, 5, 15 meq/L) were operated with 8 days of sludge residence time and an effective volume of 2 L. Results showed amount and composition of EPS was dependent on calcium and phosphorus concentrations. Except for the highest calcium concentration, increase in phosphorus concentration resulted in increase in total EPS production. Under phosphorus deficient conditions, calcium ions stimulated the production of carbohydrate type polymers and viscous bulking was observed. However, the increase in phosphorus concentration led to increase in protein type polymer production and bulking condition was cured. Addition of calcium ions increased conductivity in both cases, but increase in phosphorus concentration caused decrease in conductivity. Increase in phosphorus concentration had improved settleability, dewaterability and rheology of sludge. Moreover, effluent turbidity was decreased and COD removal efficiency was recorded as greater than 95 % for all calcium concentrations under phosphorus sufficient conditions. Microscopic analyses showed that under phosphorus deficient conditions flocs were weak, dispersed and nonresistant. Increase in phosphorus concentration resulted in improvement of floc structure. Same Enterobacter and Citrobacter species were identified at all calcium concentrations under phosphorus deficient conditions. Yet, under phosphorus sufficient conditions different species were identified in control reactor as compared to 5 meq/L and 15 meq/L concentrations.

京都大学 / 0048 / 新制・課程博士 / 博士(農学) / 甲第21147号 / 農博第2273号 / 新制||農||1058(附属図書館) / 学位論文||H30||N5121(農学部図書室) / 京都大学大学院農学研究科地域環境科学専攻 / (主査)教授 北山 兼弘, 教授 小杉 緑子, 教授 北島 薫 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DFAM

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<p> </p> <p>Phosphorus (P) is an essential macronutrient for plant growth and development. P deficiency is becoming one of the most limiting factors for crop productivity. It has been discovered that vascular tissue-mediated systemic signaling plays important roles in plant responses to P deficient growth conditions. In order to understand vascular tissue-specific molecular alterations in response to P deficiency, I used <em>Plantago major </em>as a model species to study the transcriptomic alterations in vascular tissues because it is fast and easy to dissect pure vascular tissues from this plant. I identified 237 differentially expressed genes involved in various roles to P deficiency, such as “phosphate metabolism and remobilization”, “sucrose metabolism, loading and synthesis” and “plant hormone metabolism and signal transduction”. In addition, translating ribosome affinity purification (TRAP) was used to identify 547 differentially expressed genes from the Arabidopsis vascular tissues. <em>AtERF</em>, one of the downregulated genes, was chosen for further functional characterization. My results demonstrated that <em>AtERF </em>is specifically expressed in vascular tissues and it encodes a transcription factor. Over-expression of <em>AtERF </em>led to a purple vein phenotype, decreased growth of shoots and roots, and reduced Pi concentrations in shoots and roots. The <em>erf </em>mutant plants displayed larger shoots and roots, and increased Pi concentration in shoots and roots. Molecular analysis in the over-expression and mutant plants showed that genes related to hormone metabolisms and root architecture establishment might be the major players enabling plants to cope with low P. The discoveries from this study may be used to implement strategies for the production of crops with increased P uptake efficiency. </p>

Abiotic stresses such as salinity and phosphorous (P) deficiency are major yield-limiting factors for rice, particularly on marginal lands. Marker-aided backcrossing (MAB), enabled by advances in genomics and molecular mapping in recent years, is said to be a more precise, time-saving, and cost-effective way to develop rice varieties that can withstand these abiotic stresses than conventional breeding. The study employs the economic surplus approach to measure the benefits of MAB for salinity tolerance in rice for Bangladesh, India, Indonesia, and Philippines, and for rice with tolerance to P-deficient soils in Indonesia. At a 5% discount rate, the benefits over 15 years of planting salt-tolerant varieties amount to $226.9 million in the Philippines, $3.666 billion in Bangladesh, $4.848 billion in India, and $895.7 million in Indonesia. The gains from growing varieties that can withstand P deficient soils in Indonesia amount to $2.070 billion. The incremental benefits from completing the salt-tolerant and P-deficient tolerant breeding cycles 2 years earlier are $340.5 million in Bangladesh and $192.1 in Indonesia, respectively. In India, $227.0 million is gained even if MAB develops salt-tolerant varieties just a year earlier. The additional gains from completing the salt-tolerant rice breeding cycle 4 years earlier are $40.3 million in the Philippines and $158.9 in Indonesia. In general, the gains from saline- (Bangladesh, Indonesia, Philippines) and P-deficient (Indonesia) tolerant rice are reduced by 5%, 9%, 14%, and 18% when MAB breeding cycle is delayed by one, two, three, and four years, respectively. In India, there is 3%, 7%, 10%, and 13% loss in benefits from salt-tolerant rice for every additional year of delay in the MAB breeding cycle. / Master of Science

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