control of plant growth and development ( 식물 생장과 발육 조절 ) chapter 35
TRANSCRIPT
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Control of Plant Growth and Development
( 식물 생장과 발육 조절 )
Chapter 35
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환경에 대한 식물의 반응의 예 , 햇빛의 방향을 향하고 있는 해바라기들 (Helianthus).
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Why It Matters
Gibberellin and rice
그림 35.1. 벼 (Oryza) 의 줄기생장에 대한 호르몬 지베렐린의 효과 .
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35.1 Plant Hormones
Auxins promote growth
Gibberellins also stimulate growth, including the elongation of stems
Cytokinins enhance growth and retard aging
Ethylene regulates a range of responses, including senescence
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35.1 (cont.)
Brassinosteroids regulate plant growth responses
Abscisic acid suppresses growth and influences responses to environmental stress
Jasmonates and oligosaccharins regulate growth and have roles in defense
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Auxins( 옥신 )
Mainly indole acetic acid (IAA)
Synthesized primarily in shoot apical meristem and young stems and leaves
Promote elongation of cells in coleoptiles and stems
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그림 35.2. 굴광성에 대한 다윈의 실험들 .
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그림 35.3. 귀리 자엽초에서의 IAA 의 효과를 보여주는 벤트 (Went) 의 두 가지 실험 .
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Auxin Effects on Stem and Root
그림 35.4. 치자나무 (Gardenia) 절지에 대한 옥신 처리의 효과 .
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Polar transport from tip to base
그림 35.5. 식물 조직에서의 옥신의 극성 이동에 대한 연구의 실험적 증거 .
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그림 35.6. 옥신의 극성 이동에 관한 모델 .
산성 pH
AUX1__
___
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Cell Expansion Acid-growth hypothesis( 산성생장설 )
그림 35.7. 옥신이 식물세포의 생장을 조절하는 방법 .
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Gibberellins( 지베렐린 )
GA1 is most common
Synthesized in shoot and root tips
Promote stem elongation, help seeds and buds break dormancy( 휴면타파 )
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Effects of Gibberellin
Bolting and fruit enlargement
그림 35.8. 겨울 채소인 양배추에서의 추대형성 . 그림 35.9. 씨 없는 포도에
대한 지베렐린의 효과 .
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Cytokinins( 시토키닌 )
Zeatin( 제아틴 ) is most abundant natural cytokinin
Synthesized mostly in root tips
Stimulate cell division, promote leaf expansion, and retard leaf aging
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그림 35.10. 담배 (Nicotiana tabacum) 조직 배양에서 옥신과 시토키닌의 비율의 영향 .
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Ethylene( 에틸렌 )
Ethylene gas
Present in fruits, flowers, seeds, leaves, roots
Promotes fruit ripening, senescence( 노화 ) and abscission( 탈리 )
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Abscission Zone( 탈리 부위 )
그림 35.11. 단풍나무 (Acer) 에 있는 탈리 부위 .
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Ethylene
Removal of seed pods in soybean delays senescence since ethylene is not produced
그림 35.12. 완두 (Glycine max) 꼬투리를 제거하면 노화가 지연된다는 것을 보여주는 실험 .
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Brassinosteroids( 브라시노스테로이드 )
Group of steroid hormones
Highest concentrations in shoot tips and in developing seeds and embryos
Stimulate cell division and elongation 그림 35.13.
브라시노스테로이드는 유전자 발현을 조절하여 빛에 대한 식물의 생장 반응을 중재함 .
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Abscisic acid( 앱시스산 )
ABA
Synthesized from carotenoid pigments inside plastids in leaves
Promotes stomatal closure; may trigger seed and bud dormancy
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그림 35.14. 다년생 콘플라워 (Centaurea montana) 의 눈에 있는 비늘들 ( 휴면상태 ).
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Jasmonates( 자스민산자스몬산 )
JA and oligosaccharins( 올리고당 )
Signaling roles
Regulate growth; trigger defense responses
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35.2 Plant Chemical Defenses
Jasmonate and other compounds interact in a general response to wounds
The hypersensitive response(HR) and PR proteins are other general defenses
Secondary metabolites defend against pathogens and herbivores
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35.2 (cont.)
Gene-for-gene recognition allows rapid responses to specific threats
Systemic acquired resistance(SAR) can provide long-term protection
Extremes of heat and cold also elicit protective chemical responses
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General Responses to Wounds
Hormone-induced wound responses limit damage from bacteria, fungi, worms, or plant-eating insects
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그림 35.15. 상처에 대한 시스테민 (systemin)( 펩티드 호르몬 ) 반응 .
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Hypersensitive Response( 과민성 반응 )
Isolates an infection site by surrounding it with dead cells
Salicylic acid( 살리실산 ) (SA) induces synthesis of PR (pathogenesis-related) proteins
그림 35.16. 과민성 반응의 증거 .
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Secondary Metabolites(2 차 대사물질 (산물 ))
Oligosaccharins( 올리고당 ) trigger synthesis of phytoalexins( 파이토알렉신 )
Function as antibiotics
Examples:(2 차대사물질의 예 )• Caffeine, cocaine, strychnine
• Tannins
• Terpenes: Conifer resins, essential oils
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Gene-for-Gene Recognition( 유전자 -유전자 인식 )
Enables plant to recognize pathogen chemically and mount defenses against it
Plant’s R gene
Pathogen’s Avr gene(avirulent, 비병원성 )
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그림 35.17. 유전자 - 유전자 저항성이 작동하는 방법에 대한 모델 .
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Systemic Acquired Resistance( 전신성 획득 저항 , SAR)
Provides long-term protection against some pathogens
Salicylic acid passes from infected organ to newly forming organs such as leaves, which then synthesize PR proteins
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그림 35.18. 전신성 획득저항에 대한 제안 메커니즘 .
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Heat-Shock Proteins( 열충격 단백질 )
HSPs can reversibly bind enzymes and other proteins in plant cells
Prevents denaturing when plant is under heat stress
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Antifreeze Proteins( 부동 단백질 )
Stabilize cell proteins when cells are threatened with freezing
Help maintain structural integrity of cell proteins
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35.3 Plant Responses to the Environment: Movements( 운동 ; 움직임 )
Phototropisms( 굴광성 ) are responses to light
Gravitropism( 굴중성 ) orients plant parts to the pull of gravity
Thigmotropism( 굴촉성 ) and thigmomorphogenesis( 굴촉형태발생 ) are responses to physical contact
Nastic movements( 경성 운동 ; 기울어짐 ) are nondirectional
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Phototropisms( 굴광성 )
Growth responses to directional light source
Blue light receptors trigger auxin transport
Auxin triggers differential cell elongation
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그림 35.19. 유식물에서의 굴광성 .
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Gravitropism( 굴중성 )
Growth response to Earth’s gravitational pull • Statoliths( 평형석 ) move in response to gravity
그림 35.20. 평형석 가설을 지지하는 증거 .
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Gravitropism
Mechanical stimulus from statoliths triggers auxin transport, leading to differential cell elongation
Stems exhibit negative gravitropism, growing upward, while roots show positive gravitropism
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Gravitropism
그림 35.21. 어린 줄기에서의 굴중성 반응 . 유식물을 5일간 암실에서 키운 후 , 옆으로 놓은 다음 0.5 cm 간격으로 표시 . 음성 굴중성에 의해 2 시간 이내에 줄기가 똑바로 섰음 .
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Thigmotropism( 굴촉성 )
Growth in response to contact with a solid object
그림 35.22. 지지대를 감고 있는 시계풀(Passiflora) 덩굴손에서의 굴촉성 반응 .
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Thigmomorphogenesis( 촉성형태발생 )
Mechanical stress causes the stem to add girth• Caused by frequent strong winds, rainstorms,
grazing animals, etc
그림 35.23. 토마토에 대한 물리적 스트레스의 효과 . (a) 대조군 , 온실재배 , (b) 28 일동안 280 rpm 으로 30 초간 물리적으로 흔들어 주었음 , (c) (b) 를 하루에 두번씩 행함 .
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Nastic Movements( 경성운동 )
Reversible responses to nondirectional stimuli• Movements in leaves, leaflets, flowers
그림 35.24. 콩과 식물 잎에서의 경성 수면 운동 . 23 시간 동안 계속 암 처리를 하였지만 , 수면 운동은 일출이나 일몰과 상관없이 계속되었음 .
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Nastic Movements
Sensitive plant: 미모사 (Mimosa pudica)
Mechanical stimulation triggers a membrane action potential( 활동전위 )
Water then enters or exits cells of pulvinus( 엽침 ), triggering leaf folding
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Sensitive Plant: Mimosa pudica
그림 35.25. 예민한 식물인 미모사의 소엽들의 경성 운동 .
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35.4 Plant Responses to the Environment: Biological Clocks( 생체시계 )
Circadian rhythms( 개일리듬 ; 일주기성 리듬 ) are based on 24-hour cycles
Photoperiodism( 광주기성 ) involves seasonal changes in the relative length of night and day
Cycles of light and dark often influence flowering
Dormancy is an adaptation to seasonal changes or stress
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Circadian Rhythms( 일주기성 리듬 )
24 hours cycles
Internal time-measuring mechanisms with a biochemical basis
Environmental cues can “reset” clocks• Enables seasonal adjustments in growth,
development, and reproduction
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Photoperiodism( 광주기성 )
Responses to change in relative length of daylight and darkness
Also allows biological clock to be “reset” for seasonal adjustments to day length
Controlled by phytochrome( 피토크롬 ) pigment
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Phytochrome( 피토크롬 )
Converts to active form (Pfr) during daylight, when red wavelengths dominate
Reverts to inactive form (Pr) at sunset, at night, or in shade, when far-red( 원적외선 ; 근적외선 ) wavelengths predominate
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Phytochrome Switching Mechanism
그림 35.26. 식물의 여러 부위의 생장을 촉진하거나 억제할 수 있는 피토크롬 스위치 메커니즘 .
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Phytochrome
Pfr controls types of enzymes produced in particular cells
Examples:• Seed germination
• Stem elongation
• Leaf expansion
• Flowers, fruits, seeds그림 35.27. 어린 콩과 식물에서 암실의 효과 . 카로티노이드는 합성되지만 엽록소가 합성되지 않아서 노란색임 . 대조군보다 긴 줄기 , 작은 잎 , 작은 뿌리를 가짐 .
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Flowering Responses( 개화반응 ) (1)
Long-day plants( 장일식물 ; 단야식물 )• Flower in spring or summer, when day length is
long relative to night
그림 35.28. 장일식물인 시금치에 대한 낮 길이의 영향 .
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Flowering Responses (2)
Short-day plants( 단일식물 ; 장야식물 )• Flower in late summer or autumn, when day
length is relatively short
Intermediate-day plants( 중간식물 ; 중일식물 )• In between long- and short-day plants
Day-neutral plants( 중일식물 ; 광주기 중립식물 )• Flowering not affected by photoperiod
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Night Length Controls Photoperiodism
그림 35.29. 밤의 길이가 개화에 중요하다는 것을 보여주는 실험 .
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Florigen( 화성소 ): Chemical Signals for Flowering
그림 35.30. 개화 신호 전달 경로의 모델 .
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Vernalization( 춘화처리 ) and Flowering
Vernalization (“making springlike”)• Period of low temperature stimulates flowering
• Used to force bulbs to flower for certain holidays
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Dormancy( 휴면 )
Perennial or biennial plant stops growing even though conditions appear to be suitable for continued growth
Preparation for winter
Phytochrome used to sense long nights of autumn
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Experiment: Effect of Day/Night Length
그림 35.31. 미송의 생장에 있어서 낮과 밤의 상대적 길이의 영향 . 왼쪽은 낮의 길이가 짧아서 (12 시간 ) 휴면상태에 있음 . 오른쪽은 낮의 길이를 길게 ( 밤의 길이를 짧게 ) 하여 휴면 없이 생장하도록 함 .
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Breaking Dormancy( 휴면 타파 )
Requires exposure to sufficient periods of low temperatures• Gibberellin and abscisic acid signals
그림 35.32. 라일락의 휴면하는 눈들에 대한 낮은 온도의 영향 .
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35.5 Signal Responses at the Cellular Level
Several signal response pathways operate in plants
Second messenger(2 차 신호전달자 ) systems enhance the plant cell’s response to a hormone’s signal
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Signal Response Pathways
Hormones and environmental stimuli alter behavior of target cells• Signal molecules bind to receptors( 수용체 ) in
target cells
Response pathway ultimately alters gene expression
Changes induced in cell’s shape or internal structure or influence its metabolism
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그림 35.33. 식물세포에서의 신호에 대한 반응 경로 .
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Receptors( 수용체 )
Some hormones and growth factors bind to receptors at target cell’s plasma membrane• Receptor changes shape
Binding triggers release of internal second messengers(2 차 신호전달자 )• Diffuse to nucleus and alter gene expression
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Second Messengers
Reaction sequence amplifies cell’s response to signal• Activated receptor activates series of proteins
G proteins and enzymes stimulate synthesis of second messengers (such as IP3)• Bind to ion channels on endoplasmic reticulum,
vacuole, plasma membrane, etc
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Action of Second Messengers
Bound channels open to release calcium ions• Ions enter cytoplasm and activate protein kinases
• Kinases activate specific proteins that produce cell response
• Many proteins can be activated, so signal is amplified significantly