A Study on an ABC transporter that mediates the root-to-shoot translocation of cytokinin in Arabidopsis

DoctorPlants are composed of the aboveground structure, shoot, and the belowground structure, root. The shoot conducts photosynthesis and provides the products to the root via phloem, as building blocks and energy sources. On the other hand, the root absorbs water and minerals from soil and delivers them to the shoot through xylem. Therefore, the growth and activity of the two structures are tightly associated and need to be coordinated to adapt to the ever-changing environment; alteration in root growth or activity by changes in rhizosphere alters those of shoot and vice versa. This coordination is achieved by signal molecules which translocate between root and shoot to induce responses in the distant tissues under given envrionmental conditions. Cytokinin, a phytohormone, is one of the long-distance signal molecules transported from the site of biosynthesis to the distant tissues either via xylem or phloem. For example, cytokinins of N6-(Δ2-isopentenyl)adenine (iP) type are delivered from shoot to root via phloem and regulate vasculature patterning in root apical meristem. On the other hand, supply of nitrate to rhizosphere induces biosynthesis of trans-zeatin (tZ)-type cytokinins in the root and the hormone is translocated to the shoot via xylem. A recent study revealed that the root-derived tZ-type cytokinins stimulate shoot growth. However, the molecular identity underlying the long-distance transport of the cytokinin remained elusive. The aim of this study is to identify the transporter that mediates the root-to-shoot translocation of the cytokinin. To address the question, I hypothesized that the transporter would be expressed in spatiotemporally similar way with rate-limiting enzymes for cytokinin biosynthesis in the root. Therefore, I established the following three criteria to search for the candidate transporters using In silico database; (i) The transporter would be highly co-expressed with adenosine phosphate isopentenyltransferase 3, one of the most important enzymes for cytokinin biosynthesis; (ii) The transporter would be primarily expressed in root phloem companion cells where cytokinins are actively produced; (iii) The transporter would be up-regulated in transcription by cytokinin treatment. I screened transporters based on the criteria and found only one transporter, AtABCG14, which satisfied all the criteria. The high expression of the transporter in the cells synthesizing the cytokinins was confirmed by analysis of the AtABCG14 expression pattern in transgenic plants carrying reporter genes under the control of AtABCG14 promoter. The atabcg14 knockout mutant exhibited shoot growth retardation that was reminiscent of cytokinin-deficient mutants, but it was recovered by exogenously applied tZ. The results suggested that lack of tZ in the mutant shoot might cause the growth defects. As predicted, the content of tZ-type cytokinins in the mutant shoot was significantly decreased but increased in the mutant root compared to those of the wild type with the consistent changes in the expression level of cytokinin response genes. In addition, tZ-type cytokinins in the mutant xylem sap were dramatically reduced by ~90% compared to that of wild type, indicating that AtABCG14 plays crucial roles in the xylem loading and the acropetal transport of the cytokinins. Consistently, the translocation of 14C-labled tZ from root to shoot was significantly delayed in the mutant in comparison with the wild type. Grafting of atabcg14 scion onto the wild-type rootstock rescued the growth of the mutant shoot while the wild-type scion grafted on the mutant rootstock exhibited shoot growth defects. These results strongly indicate that AtABCG14 mediates the root-to-shoot translocation of cytokinin, which is important for the shoot growth. This study revealed the long-sought molecular identity for the acropetal transport of cytokinin. AtABCG14 is a first transporter, which showed physiological relevance by mediating the long-distance cytokinin transport. Therefore, this study provides new opportunities for investigating and manipulating the cytokinin-dependent pathways as well as cytokinin transport

Introduction to Marine Energy Technical Standards in China

최근 중국은 급속한 경제 성장과 함께 재생에너지 소비비율이 해마다 증가하고 있으며, 관련 시장 또한 성장하고 있다. 해양에너지는 중국 에너지 시장에서 점점 더 중요한 역할을 해오고 있으며, 2016년 중국발전개혁위원회에서는 제13차 재생에너지 개발 5개년 계획을 수립하여 해양에너지 기술의 종합적인 활용을 위한 R&D 강화를 제안하였다. 또한 중국 자연자원부에서는 해양에너지 산업 형성과 관리에 초점을 두고 정책을 추진하고 있다. 이처럼 중국은 경제성장과 함께 해양에너지에 많은 투자가 이뤄지고 있으며, 또한 국제 시장에 대응하기 위한 국가 기술 표준을 제정하고 있다. 이에 본 연구에서는 중국 해양에너지 기술 현황 및 표준을 소개하고자 한다.2

A revision status of the technical specification for electricity producing tidal energy converters-power performance assessment in IEC/TC114 MT-200

이 발표에서는 국제전기기술위원회(IEC, International Electrotechnical Commission) 산하 해 양에너지 분야 기술위원회인 TC114(Technical Committee 114)에서 발행한 조류발전기에 대한 출 력성능평가 기준에 대한 개정 작업에 대한 내용을 소개하고자한다. IEC/TC114는 지난 2013년 5월 출간된 조류발전기에 대한 출력성능평가 기준, 즉 IEC/TS62600-200(Marine Energy-Wave, Tidal and Other Water Current Converters - Part 200: Electricity producing tidal energy converters - Power performance assessment)에 대한 Ed2.0 발행을 위하여, 기존 TS62600-200에 대한 AHG(ad hoc group) 을 작년 하반기 중 MT(maintenance team)으로 개편하고, 현재 개정 작업을 수행하고 있다. 현재 논의 되고 있는 개정 내용으로는, 애매한 용어 및 IEC/TS62600-1 용어편 및 타 기술규격서와 일치하지 않는 용어에 대한 보완, Ed1.0에는 구체적인 내용이 없었던 8.9.2 Contribution from turbulence, 8.9.3 Contribution from waves 항에 대한 보완, 그리고 계측불확도(measurement uncertainty)에 대한 부분 등이 있다. 현재 MT-200에서는 2019년 6월 CD(committee draft)를, 2020년 5월 DTS(draft technical specification)을 제출하고, 승인을 받아 2020년 12월 TS62600-200 Ed2.0을 발행할 계획이다.2

해양에너지 산업의 중대사고 위험 관리에 관한 신규 작업 항목 제안

최근 해양에너지 시스템에 대한 실해역 실증시험 증가로 다양한 중대 사고에 노출되어 있다. 그러나 작업자의 안전 확보 및 환경 피해 저감에 대한 대책은 미흡하며, 중대 사고에 대한 관리 방안 또한 수립되어 있지 않다. 이에 전 세계적으로 해양에너지 분야에 대한 체계적인 중 대사고 관리 기준 정립이 필요하며, 이를 위한 최소 요구사항을 규정할 필요가 있다. 이에 본 연구에서는 IEC TC 114 신규 작업 항목으로 해양에너지 산업의 중대사고 위험 관리를 제안하였으며 이 내용에 대해 소개하고자 한다. 향후 본 신규 항목에 대한 회원국의 동의가 필요하 며, 위험성평가 등 위험 관리를 위한 절차를 마련하고자 한다.2

Analysis of Vertical Profile Characteristics in Jangjuk Strait using Layered Tidal Field Measurement Data

Various mathematical models have been proposed to estimate the vertical tidal current profile. However, because the parameters of these models depend on specific site conditions such as seabed conditions and viscosity, it is recommended to estimate them using field-measured data. In particular, tidal current energy sites with fast tidal velocities exhibit different vertical tidal current profile characteristics from general sea areas, making it essential to estimate these profiles using field-measured data for practical purposes. In this study, layered tidal currents were measured over two months using an acoustic Doppler current profiler to analyze the vertical tidal current profiles at two sites in Jangjuk Strait, a candidate site for tidal current energy. Based on the field-measured data, the profiles were fitted using power law and logarithmic profile models, and the parameters were estimated for both flood and ebb tides with a velocity bin set at 1 m/s intervals. The analysis results indicated that at JSD-1, the power law parameter was estimated to be 7.50 during flood tide and 9.49 during ebb tide, with an average bed roughness of 0.42. Additionally, the roughness length, which represents seabed roughness in the logarithmic profile, was estimated at 0.022 m during flood tide and 0.011 m during ebb tide, while the friction velocity was estimated at 0.115 m/s during flood tide and 0.073 m/s during ebb tide. At JSD-2, the power law parameter was estimated at 7.40 during flood tide and 10.30 during ebb tide, with an average bed roughness of 0.41. Additionally, the roughness length was estimated at 0.020 m during flood tide and 0.005 m during ebb tide, while the friction velocity was estimated at 0.118 m/s during flood tide and 0.074 m/s during ebb tide. Finally, a correlation analysis between the parameters confirmed a positive correlation between the depth-averaged tidal current velocities and friction velocities. Tidal current energy sites display characteristics different from other sea areas; hence, it is necessary to consider field conditions when analyzing layered tidal characteristics or conducting numerical ocean modeling.22Nkc

Establishment Plan for Sea Test Bed for Tidal Current Energy Converters in Korea

The world’s energy consumption has been increasing and global warming has been getting more serious. Because of this, eco-friendly energy policies are being established in Korea.Especially, Korean energy policy has been changed with the beginning of nuclear power phaseout and development of new and renewable energy. There has been a lot of interests in the development of marine energy. Among marine energy technology, tidal current energy is the closest technology to the commercialization. In particular, the southwestern coast of Korea is the candidate site for the development of tidal current energy. Because there are strong velocities occurring between islands. MOF(Ministry of Oceans and Fisheries) has planned for the Strategic Plan for Development and Support of New and Renewable Energy such as Ocean Energy in 2017. Meanwhile, KIOST(Korea Institute of Ocean Science & Technology) is developing sea test bed for tidal current energy converters at Jang-Juk strait and Uldolmok. And MOF is supporting the construction projects of the open sea test sites for tidal current energy converters from 2017. Thus, in this paper, establishment plan for sea test bed is introduced. The sea test bed was titled K-TEC(Korea Tidal current Energy Center). The project for open sea test bed with 5 berths of 4.5 MW grid-connected capacity for the tidal energy converters is scheduled from April 2017 to December 2022 by KIOST.2

Analysis on the Emersion and Submersion Patterns of the Coastal Zone in Korea

연안 해역의 노출 및 침수양상은 연안 서식생물의 서식환경에 직접적인 영향을 미치는 중요한 인자이다. 본 연구에서는 우리나라 연안 8개 지점의 조위자료를 이용하여 연안의 노출 및 침수양상을 빈도에 따라 5개의 영역으로 구분하고, 구분된 영역의 특성 분석을 수행하기 위하여 기존의 AHHW, ALLW 기준조위와 더불어 국제적인 기준조위로 널리 이용되는 HAT, LAT 기준조위를 추정하였다. 연안 8개 지점에 대한 노출 및 침수형태를 분류된 5가지 종류의 구역 중심으로 분석한 결과, 모든 지점에서 1일 2회의 노출과 침수가 발생하는 영역 3의 점유시간 빈도가 87.2-88.2% 범위로 가장 우세한 것으로 파악되었으며, 조위와는 무관하게 비교적 일정한 비율을 유지하는 것으로 파악되었으며, 영역 2, 4는 각각 4% 이하, 8% 이상의 비율을 유지하고 있다. 한편, 조석 형태수에 의하면 일주조 우세로 분류되는 포항에서는 조석의 뚜렷한 연주조와 반년주조의 영향으로 그 비율이 각각 1.4%, 10.8% 정도로 증감하는 양상을 보이고 있다. The submersion and emersion patterns are key factors that directly influence the habitat environment of the coastal plants and animals. In this study, the coasts are divided into five zones (zones 1, 2, 3, 4, and 5 - not flooded, flooded once, flooded and exposed to air twice, exposed to air once, continuously flooded in the day, respectively) based on the patterns using tidal elevation data at the major eight stations and the domestic and international reference tidal levels, i.e., AHHW, ALLW, HAT and LAT, are also estimated to analyse the characteristics of the five distinct zones. Based on the results, the frequency of the zone 3 are dominant and forms from 87.2% to 88.2% (nearly constant) irrelevant with the tidal ranges at all stations. The taking-up percentages of the zones 2 and 4 show nearly constant, below 4% and over 8%, respectively. In Pohang station classified as the mainly diurnal tide, the percentages are decreased to 1.4% in zone 2 and increased to 10.8% due to the effects of the annual and semi-annual tidal components.22Nkc

Statistical Characteristics of Hourly Tidal Levels around the Korean Peninsula

Representative tidal gauging (TG) stations are selected to cover the tidal characteristics of the Korean peninsula coastal seas, and the statistical parameters of the data are analysed from the perspective of the probability distribution at that TG station. The shape of the distribution in the Incheon and Gunsan TG stations, which are tide-dominated areas, shows two clear modes at HWONT and LWONT in the distributions, and in the Mokpo station, shows an asymmetric double peak distribution. In contrast, the frequency distribution shape shows a smoothed flat peak in the Jeju, Yeosu and Busan TG stations, and a single peak in the Pohang and Sokcho TG stations. The emersion and submersion equations suggested as the 6-parameter Gaussian mixture models in this study are accurate, and well fitted to the observed tidal elevation data. The μ1 , μ2 parameters are highly correlated to the LWONT and HWONT, and the σ1 and σ2 parameters are also closely correlated to the mean tidal range. The μ1 and μ2 parameters coincide with the modes of the suggested probability distribution of the hourly tidal level data. 한반도 연안 주요 조위관측소 조위자료를 선정하여 확률분포 측면에서 분석을 수행함으로써 조위 특성 및 통계적인 매개변수들을 분석하였다. 조석현상이 우세한 인천과 군산 자료의 조위확률 분포는 HWONT와 LWONT에서 2개의 대칭형 첨두형태를 보이고, 목포 자료의 경우 비대칭형 첨두형태를 보이고 있다. 반면에 제주, 여수, 부산 자료의 경우 편평한 첨두형태를 보이고, 포항, 속초 자료의 경우 1개의 첨두형태를 보이고 있다. 본 연구에서 노출과 침수 관계식으로 제안한 6개의 매개변수를 가진 가우스 혼합분포 모형은 정확하고, 관측결과와도 잘 일치하고 있다. μ1 , μ2 매개변수는 LWONT, HWONT와 σ1 , σ2 매개변수는 평균조차와 밀접하다. μ1 , μ2 는 제안한 확률분포의 최빈값에 해당한다.22Nkc