Application of Salt-tolerant and Nitrogen-fixing Blue-green Algae to Agriculture in Sea Water

我们克隆了耐盐植物分子育种所必需的基因，如四氢嘧啶合成基因、水稻HKT基因和酵母ENA 1基因。由于这些基因不足以实现最终目标，因此克隆了其他基因并分析了它们的功能。过量表达水稻钾离子转运蛋白OsHAK 5基因的烟草BY2细胞能在低钾培养基中生长并表现出耐盐性。过量表达烟草HAL 3基因可提高BY2细胞的耐盐性，氮源的供应将是耐盐植物在海水中生长的一个重要因素。从冲绳附近海域分离到的单细胞蓝绿藻Synechococcus sp. TU 126具有固定大气氮的能力，可在无碳源和无氮源的人工海水中生长。在25℃光照条件下培养14天和45天的聚球藻，胞内总氮分别为19.22mg/l和41.8mg/l，分泌氮分别为3.2mg/l和4.2mg/l。在条件培养基含氮量相同的情况下，披衣菌W80在聚球藻的条件培养基中的生长量与在含NH_4Cl的新鲜培养基中的生长量相同，表明聚球藻产生的含氮化合物可被植物利用。藻酸钙固定化的聚球藻细胞在培养30天和60天后分别分泌1.0 mg/l和5.6 mg/l的氮。因此，固定化聚球藻TU 126可以作为耐盐植物的氮源用于海水农业生产。

We have cloned essential genes required for molecular breeding of salt-tolerant plants which can grow in sea water, such as ectoine synthetic genes, rice HKT gene and yeast ENA1 gene. Since these genes were not enough for the final goal, other genes were cloned and analyzed their function. Tobacco BY2 cell, which was over-expressed rice potassium ion transporter, OsHAK5 gene, can grow in low potassium ion medium and showed salt-tolerance. BY2 cell increased salt tolerance when it was over-expressed tobacco HAL3 gene which participate to praline accumulation.Supply of nitrogen source will be an important factor when salt-tolerant plants are grown in sea water. Single-cell blue-green algae, Synechococcus sp.TU126, which was isolated from sea water near from Okinawa can fix atmosphere nitrogen and grew in artificial sea water without carbon and nitrogen source. Total intracellular nitrogen in the Synechococcus grown in artificial sea water under light at 25℃ for 14 days and 45 days, was 19.22 mg/l、 41.8mg/l, respectively, and excreted 3.2 mg/l、4.2 mg/l nitrogen, respectively, in the medium.Salt-tolerant green algae, Clamydomonas sp.W80 grew in the conditioned medium of the Synechococcus in the same extent as that in the fresh medium contained NH_4 Cl in the same level of nitrogen in the conditioned medium, suggesting that nitrogen compounds produced by the Synechococcus can be utilized by plants. Immobilized Synechococcus cells in calcium alginate secreted nitrogen of 1.0 mg/l and 5.6 mg/l in culture medium after 30 days and 60 days, respectively. In conclusion, salt-tolerant plants can be supplied nitrogen source from immobilized Synechococcus sp.TU126 in agriculture in sea water.