Langfristige Versorgung groBer Gemusepflanzen mit Stickstoff uber Becherdepots, dargestellt an den Kulturen WeiBkohl(Brassica oleracea L.), Gurken(Cucumis sativus L.) und Tomaten (Lycopersicon esculentum Mill.)

국문 초록 (Abstract)

토마토, 오이, 피망, 멜론등은 시설재배시 뿐만 아니라 노지재배시 집약적인 관수를 요구하며, 높은 면적생산성을 가진 채소작물이다. 이 채소작물들은 또한 전 생육기간에 높고, 지속적인 질소요구도를 갖고 있다.

화학비료를 분배시용하는 관행시비나 완효성질소비료의 투입, 혹은 관비에 의한 시비방법으로는 이 채소작물들의 높은 질소요구도를 충족 시킬수 없으며, 시용된 질소가 부분적으로 용탈되거나 탈질되어 유실된다.

집약적인 채소재배로 인한 환경오염문제를 해결하고자 CULTAN방식에 의하여 암모늄태질소를 질소공급원으로 하여 Beaker안에 충진하여 만든 환경친화형 NH₄-Beaker deposit비료를 개발하였다. Beaker deposit비료의 단일시비로 Deposit beaker안에 들어있는 질소를 작물이 생육초기부터 후기까지 흡수하게 되며, 이 질소는 암모늄이 갖고 있는 독성과 뿌리의 생육을 Attraction하는 특성 때문에 작물의 생육상태에 맞추어, 조절되어 흡수된다.

본 시험에서는 (NH₄)₂SO₄와 CO(NH₂)₂를 1대 2의 비율로 혼합하여 확산완충물질과 함께 PVC-Beaker안으로 충진하였다. 지속적이고 균일한 질소의 용출과 확산구매를 형성하기 위하여 점토질토양을 점결제로 사용하였으며, Beaker는 개열구가 밑으로 향하게 하여 유묘의 정식기에 지중 식물뿌리 부분으로 삽입하였다.

CULTAN방식에 의하여 제작된 Beaker deposit비료를 작물의 생육초기에 질소공급원으로 단일시비하였을 때 관행시비구보가 최소한 동등한, 보편적으로 높은 수확량과 질소공급 효과를 얻을수가 있었으며, 또한 용탈이나 탈질로 인한 질소의 유실을 방지할 수 있었다.

본 실험결과들에 의하면 Beaker deposit비료를 농가 채소작물재배에 질소 비료의 공급원으로 사용하는 것이 환경적인 면에서나 경제적인 면에서 타당성이 높은 것으로 판단된다. 미량원소나 역제제, 또는 생장조절제등을 Deposit beaker안으로 혼합충진하면 더 좋은 효과들을 기대해 볼 수 있다.

다국어 초록 (Multilingual Abstract)

The bacteriophage λO protein localizes the initiation of replication to a unique sequence, ori λ through specific protein-DNA and protein-protein interactions.
Conformational changes at ori λ introduced by O protein binding have been reported and their roles have been implicated in the initiation of λ DNA replication. In our studies, we focused on detailed structural basis of the formation of the O protein-ori λ complex(O-some). This work was divided into five Chapters including a general introduction given in Chapter 1, a brief review of genetic, biochemical, and structural data for understanding the mechanism of the initiation of λ DNA replication. As shown in Chapter 2, we found that the O protein exists as a dimer and demonstrated that the active DNA binding species is also a dimer. Dimerization and sequence-specific DNA recognition are specifically mediated through the amino-terminal half of O(O1-162(아래첨자 1-162입력불가)). The binding affinity of O for a single copy of its 19 bp recognition sequence was 2-3 nM.
We also found that the O-some is composed of 4 dimers of O and ori λ DNA, which contains four 19 bp direct repeat recognition sites, i, e., a dimer of O is bound to each repeat(iteron). Moreover, we found that only the amino-terminal DNA binding domain is required for formation of the O-some.
To investigate the structural basis for the unique properties of O protein, we generated a number of carboxy-terminal and internal and internal deletion mutants of O. Experiments with purified mutant proteins, as shown in Chapter 3, indicated that (ⅰ) the deletion mutant retaining amino acid residues 19-110 is the smallest O protein species that can both bind to DNA and form a dimer, (ⅱ) the affinities of all mutant proteins for a single iteron are almost the same, ranging from 2 to 4 nM; (ⅲ) the portion of O that is responsible for dimerization is located between amino acid residues 19 and 85; (ⅳ) the carboxy-terminal domain (O 156-299(아래첨자 156-299입력불가)) is a monomeric species that does not recognize specific DNA sequences but instead, bind non-specifically to duplex DNA; (ⅴ) the linker joining the two structural domains is not required for O function, but its coding sequence of DNA contains several recognition sites for O protein (ori λ); and (ⅵ) a deletion!
m!
utant missing the amino-terminal portion of the carboxyl-terminal domain is still comparably active in the in vitro λdv replication assay.
In Chapter 4, the structural basis of the O protein-DNA complex was studied in detail. Hydroxy radical footprinting was employed to obtain the high resolution structural information about the contacts between the protein and the sugar-phosphate backbone of DNA. The missing nucleoside experiment allowed us to identify energetically important base moieties that may be in contact with bound O protein.
Quantitation of the extent of O-mediated DNA bending indicated that O induces a relatively sharp bend in an individual recognition sequence of 85。 ±5。 . Measurement of the O-induced topological change indicated that a region of DNA or specifically ori λis wrapped around the O protein core in a left-handed fashion with a linking number change of 0.7±0.1 turn.
In Chapter 5, we present direct evidence that the O protein also has the capacity to interact with single-stranded DNA, the first such interaction discovered among prokaryotic origin-binding proteins. The implication of this dual DNA binding specificity of O for the formation of the unwound structure at the A/T-rich region of ori λ is dis cussed. The addition of the λP-DnaB comple x to the O-some produces a new nucleoprotein species with a super-shift in migration. The presence of P and DnaB reduces significantly the amount of O required for binding to single-stranded DNA.
Based on these results, we propose a detailed model for sequential structural changes in ori λ as a consequence of O binding to the origin of λreplication.