오이 떡잎의 발달 과정에서 carnitine의 검출과 변화

국문 초록 (Abstract)

지방 저장 종자의 발아 시 저장 지방의 유동은 떡잎이 스스로 광합성을 하기 전까지 탄소 에너지원을 공급하기 위한 핵심적인 대사과정이다. 본 연구에서는 오이 종자의 발아와 유식물의 발달 및 노쇠화 과정의 떡잎에서 식물성 카니틴의 검출과 변화를 처음으로 보고하고자 한다. 또한 오이 떡잎의 전 발달과정에서 불포화 지방산의 변화를 조사하였다. 카니틴은 오이 종자의 파종 후 3일째 떡잎에서 14.5 nM 수준으로 최고조에 달하며, 4일째에는 그 절반 수준인 7.2 nM 수준으로 급격하게 감소하였다. 이후 이어지는 3일 동안 7일째까지 카니틴은 ~3.0 nM 수준을 유지하였다. 같은 시기 불포화 지방산의 함량은 카니틴이 최고조에 달하는 파종 후 3일째 급격히 떨어지고, 5일째 저장 지방은 완전히 고갈되는 것으로 보인다. 파종 9일째부터 카니틴은 검출되지 않았으나 떡잎이 절반 노랗게 변한 노쇠화 중기의 떡잎에서 6.8 nM 수준으로 검출되었는데, 이 검출량은 오이 종자의 파종 후 저장 지방이 고갈되어가는 4일째 떡잎에서 검출된 카니틴의 양과 비슷한 수준이다. 파종 5일 이후 광합성 기능을 완전히 확보한 녹색 떡잎에서 불포화 지방산은 일정한 수준을 유지하며, 노쇠화 단계에 접어든 떡잎에서는 세포의 내막구조물들이 파괴되며 또다시 불포화 지방산의 함량이 다소 증가하는 것을 관찰할 수 있었다. 이러한 카니틴과 불포화 지방산의 검출과 변화의 관찰은 오이 떡잎의 발달과정에서 밝혀진 최초의 발견이다. 이것은 오이 종자의 발아와 떡잎의 발달과정에 카니틴 대사와 관련 BOU 유전자 발현이 밀접하게 공조함을 확인한 것이다. 또한 오이종자의 발아과정에 에너지를 공급하기 위한 글라이옥실산 회로와 더불어 부가적인 탄소원 이동의 경로의 가능성을 뒷받침한다.

다국어 초록 (Multilingual Abstract)

Mobilization of storage lipids is critical for the germination of oil seeds, as they supply carbon and energy until photosynthesis commences in cotyledons. In this study, we determined the levels of plant carnitine and associated changes in these levels from seed germination to cotyledon senescence. We also examined changes in the content of unsaturated fatty acids throughout seedling development. Carnitine levels peaked on day 3 at 14.5 nM in cotyledons and decreased sharply to 7.2 nM on day 4. On development day 3 carnitine levels were maintained at around 3 nM until day 7. The unsaturated fatty acid content dropped by half at the same time as carnitine peaked (day-3), and storage lipids were almost depleted by day 5. Thereafter, carnitine was hardly detected until the second stage of cotyledon senescence, at which stage the carnitine content was 6.8 nM, similar to that on day 4 at the time of fatty acid depletion in the cotyledons. Unsaturated fatty acids levels remained constant in green cotyledons but slightly increased in the senescing cotyledons. The latter can be explained by intracellular breakdown of membrane lipids. This is the first such discovery in developing cotyledons and may offer clues regarding other roles of the acetyl unit transport system in plants. The expression of BOU was closely associated with carnitine metabolism during seed germination and cotyledon development. The results provide support for the possibility of carbon re-routing during the glyoxylate cycle in the supply of energy for early germination and development.

목차 (Table of Contents)

• 서론
• 재료 및 방법
• 결과 및 고찰
• References
• 초록

참고문헌 (Reference)

1 Hoppel, C, "The role of carnitine in normal and altered fatty acid metabolism" 41 (41): S4-S12, 2003

2 Reynolds, S. J., "The isocitrate lyase gene of cucumber : Isolation, characterization and expression in cotyledons following seed germination" 27 : 487-497, 1995

3 Fiume, M. M., "Tentative safety assessment; Cucumis sativus (Cucumber) -Derived ingredients as used in cosmetics"

4 Pinfield-Wells, H., "Sucrose rescues seedling establishment but not germination of Arabidopsis mutants disrupted in peroxisomal fatty acid catabolism" 43 : 861-872, 2005

5 Penfield, S., "Storage reserve mobilization and seedling establishment in Arabidopsis" 4 : 1-17, 2006

6 Weir, E. M., "Regulation of glyoxysomal enzymes during germination of cucumber, Temporal changes in translatable mRNAs for isocitrate lyase and malate synthase" 112 : 469-477, 1980

7 Eastmond, P. J., "Re-examining the role of the glyoxylate cycle in oilseeds" 6 : 72-78, 2001

8 Schwadbedissen-Gerbling, H., "Purification and characterization of carnitine acyltransferase from higher plant mitochondria" 39 : 39-44, 1995

9 Kim, D. J., "Molecular cloning of cucumber phosphoenolpyruvate carboxykinase and developmental regulation of gene expression" 26 : 423-434, 1994

10 차현정, "Metabolic Gene Expression in Lipid Metabolism during Cotyledon Development in Cucumbers and the Possibility of a Secondary Transport Route of Acetyl Units" 한국생명과학회 24 (24): 1055-1062, 2014

11 Munshi, S. K., "Lipid composition in fast and slow germination sunflower(Helianthus annuus L. )seeds" 33 : 235-246, 2007

12 Strijbis, K., "Intracellular acetyl unit transport in fungal darbon metabolism" 9 : 1809-1815, 2010

13 Graham, I. A., "Induction of malate synthase gene expression in senescent and detached organs of cucumber" 4 : 349-357, 1992

14 Smith, S. M, "Does the glyoxylate cycle have an anaplerotic function in plants?" 7 : 12-13, 2002

15 Graham, I. A., "Developmental regulation of expression of the malate synthase gene in transgenic plants" 15 : 539-549, 1990

16 Robinson, R. W., "Cucurbits" CAB International 34-38, 1997

17 Footitt, S., "Control of germination and lipid mobilization by COMATOSE, the Arabidopsis homologue of human ALDP" 21 : 2912-2922, 2002

18 Watanabe, M., "Comprehensive dissection of spatiotemporal metabolic shifts in primary, secondary, and lipid metabolism during developmental senescence in Arabidopsis" 162 : 1290-1310, 2013

19 Rylott, E. L., "Co-ordinate regulation of genes involved in storage lipid mobilization in Arabidopsis thaliana" 29 : 283-287, 2001

20 Cha, H. J., "Assay of L-carnitine in developing cucumber cotyledon" 33 : 43-50, 2017

21 Chen, Z. H., "Are isocitrate lyase and phosphoenolpyruvate carboxykinase involved in gluconeogenesis during senescence of barley leaves and cucumber cotyledons?" 41 : 960-967, 2000

22 Pracharoenwattana, I., "Arabidopsis peroxisomal citrate synthase is required for fatty acid respiration and seed germination" 17 : 2037-2048, 2005

23 Lawand, S., "Arabidopsis A BOUT DE SOUFFLE, which is homologous with mammalian carnitine acyl carrier, is required for postembryonic growth in the light" 14 : 2161-2173, 2002

24 Eisenhut, M., "Arabidopsis A BOUT DE SOUFFLE is a putative mitochondrial transporter involved in photorespiratory metabolism and is required for meristem growth at ambient CO₂levels" 73 : 836-849, 2013

25 Nguyen, P. J., "Acylcarnitines participate in developmental processes associated to lipid metabolism in plants" 243 : 1011-1022, 2016

26 Folch, J., "A simple method for the isolation and purification of total lipids from animal tissues" 226 : 497-509, 1957

27 Reis, A., "A comparison of five lipid extraction solvent systems for lipidomic studies of human LDL" 54 : 1812-1824, 2013