Study on the relationship between phytochrome-regulated genes and a latitudinal cline in FR-dependent leaf senescence

Doctor식물과 같은 고착생물들은 주변 환경에 적응하기 위해 환경에 따라 다양한 형질이 선택적으로 진화되어 왔고, 때로는 위도 기울기에 따른 환경 변화에 맞추어 식물의 형질에서도 위도에 따른 기울기가 나타난다. 최근, 잎의 노화와 위도의 기울기 사이에 상관관계가 보고 되었지만 어떤 환경요소가 중요하게 작용하는지에 대해서는 여전히 불명확하다. 위도에 따라 태양광 내 근적외선의 비율이나 노출되는 시간이 다르다는 것이 잘 알려져 있는데, 이러한 근적외선 신호가 위도에 따른 잎의 노화에 중요한지 알기 위해 우리는 18가지의 애기장대 생태형을 가지고 실험하였다. 그 결과, 근적외선을 처리한 경우에 고위도에 존재하는 애기장대 생태형일수록 잎의 노화 시기가 점점 더 빨라지는 것을 확인할 수 있었고, 노화 척도와 위도 사이의 경향성 (correlation)도 유의미하게 나타났다. 위도에 따른 잎의 노화 기울기에 어떤 유전자들이 관여하는지 알기 위해, 근적외선과 관련된 광수용체인 phytochrome A (phyA)와 phyB 돌여변이를 가지고 잎의 노화를 관찰하였다. 근적외선 조건에서 phyA 돌연변이는 야생종에 비해 빨라진 노화 표현형을 보인 반면, phyB 돌연변이에서는 잎의 노화가 지연된 것을 알 수 있었다. 그리고 이 식물들을 가지고 전사체 분석을 하여 각 돌연변이의 노화 표현형을 뒷받침하는 유전자들을 찾아냈고, 실제 이 유전자들의 발현 또한 위도와 유의미한 경향성을 보이는 것을 확인할 수 있었다. 이런 결과들을 통해, 근적외선에 의한 상반된 phyA와 phyB의 기능이 하위 유전자들의 발현에 영향을 주어 잎의 노화를 세밀하게 조절한다는 것을 알 수 있었고, 이런 조절 기작은 아마도 실제 위도에 따라 분포되어 있는 식물들이 각자의 환경에 적응하도록 도와주는 방법으로 진화되어 왔을 것이다.Environmental gradients across the latitudinal ranges of sessile organisms such as plants produce phenotypic clines through selection of adaptive genetic variation. Despite recent report of latitudinal clines in leaf senescence, the relationship between light quality and latitudinal differences in leaf senescence responses remains unclear. As the timing and duration of far-red (FR) light differs with latitude, it provides geographical information. Here, we found that Arabidopsis accessions exposed to FR light showed a strong correlation between leaf senescence phenotypes and latitude of origin. In addition, phytochrome A (phyA) and B (phyB) mutants showed early and delayed senescence in FR light, respectively. Transcriptomic analysis using phyA and phyB mutants in FR identified differentially expressed genes in leaf senescence related processes such as light, phytohormones, temperature, photosynthesis, and defense. These genes were oppositely regulated by phyA and phyB, supporting that antagonistic regulation of phyA and phyB was coupled in FR-dependent leaf senescence. Furthermore, expression of representative genes associated with FR-dependent leaf senescence correlated with latitude of origin and senescence phenotypes of Arabidopsis accessions, suggesting that genes regulated by phyA and phyB are involved in latitudinal leaf senescence in FR light. Variation in this regulatory mode between Arabidopsis accessions may therefore contribute to latitudinal adaptation

차량 애드-혹 네트워크에서의 효율적인 익명 인증 기법 연구

학위논문(석사) - 한국과학기술원 : 전산학과, 2011.2, [ vi, 30 p. ]Vehicular Ad-hoc Networks (VANETs) are one of typical application of wireless communication technology, which provide communications among nearby vehicles and between vehicles and roadside units (RSUs) connected the infrastructure. VANETs provide a perfect way to collect dynamic traffic information and sense various physical conditions related to traffic distribution with very low cost and high accuracy, which have a great potential to revolutionize driving environment, and will undoubtedly play an important role in the future transportation system. However, it is clear that security and privacy enhancing mechanisms are necessary, which are in fact a prerequisite for deployment. This has been recently well understood in academia, the industry, and among authorities. And a large number of agreed efforts have been undertaken to design security architectures for VANET systems. Extensive research efforts have been made by both industry and academia to make VANETs secure. In this thesis, we proposed a novel anonymous authentication scheme in VANETs. Our proposed scheme guarantees authentication, anonymity, unlinkability, and traceability simultaneously. The unlinkability which enables privacy preservation and the traceability which enables conditional tracking are contradictory. We utilize the traceable ring signature scheme with the $k$ -times anonymous authentication scheme to address the contradictory between the unlinkability and the traceability. Our scheme also uses elliptic curve cryptosystem to achieve storage, computation, and communication efficiency. Compared with existing works, we claim that our scheme has better performance in terms of storage, computation, and communication overhead. In addition, our scheme has three advantages compared with other previous works. First, our scheme doesn`t have revocation list update process in authentication process. Second, our scheme always provides unlinkability although multiple RSUs are compromised. Finally, our ...한국과학기술원 : 전산학과

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