Study on hypocotyl negative gravitropism inhibition by phytochrome in Arabidopsis애기장대에서의 피토크롬의 배축 음성 굴중성 방해기전 연구

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Hypocotyl negative gravitropism is one of major physiological responses regulated by phytochrome which determines fitness of seedlings by enhancing phototropic response. Phytochrome inhibits hypocotyl negative gravitropism by randomizing the orientation of hypocotyl which is first identified by up-straight growth of phytochrome mutants. PifQ mutant (pif1; pif3; pif4; pif5) showed agravitropism in dark condition and lack endodermal starch granule, while only endodermal PIF1 expression in pifQ was sufficient to rescue the agravitropism of pifQ by rescuing endodermal starch granule, most well-known gravity sensor of hypocotyl. Moreover, endodermal PIF3dN expression in wild type induced agravitropism in dark condition, suggests endodermal PIFs induce hypocotyl negative gravitropism by stabilization of endodermal starch granule. To identify phytochrome functions in cell-autonomous manner, I analyzed several tissue-specific PHYB expressing lines, and figured out epidermal phyB inhibits hypocotyl negative gravitropism while endodermal phyB could not in continuous red light grown seedlings. Epidermal PHYB expressing line stained weaker than endodermal PHYB expressing line for endodermal starch granule in continuous red light grown seedlings. Moreover, epidermal phyB induced degradation of endodermal PIFs in similar kinetics with endogenous phyB. In conclusion, epidermal phyB generates mobile signal to endodermal PIFs, subsequently inducing PIF degradation to inhibit hypocotyl negative gravitropism. As an independent study, I studied hypocotyl orientation of bzr1-1D, which was bent to root-ward in continuous red light grown seedlings. This required phytochrome, and bending proportion was increased by increasing dose of exogenous brassinosteroid in wild type. Genetic analysis with various gravitropism-required genes indicated hypocotyl bending of bzr1-1D also requires gravitropism-processing-genes. Surprisingly, red light induced endodermal starch granules of bzr1-1D to mobilize toward cotyledon-side of endodermis asymmetrically in both endodermis before hypocotyl bends. Moreover, PIN3 asymmetrically re-localized and resulted in asymmetric auxin distribution. In conclusion, I propose phytochrome induce hypocotyl bending in accordance with relative brassinosteroid signaling activity to inhibit hypocotyl negative gravitropism.
Advisors
Choi, Giltsuresearcher최길주researcher
Description
한국과학기술원 :생명과학과,
Publisher
한국과학기술원
Issue Date
2017
Identifier
325007
Language
eng
Description

학위논문(박사) - 한국과학기술원 : 생명과학과, 2017.2,[vi, 182 p. :]

Keywords

Phytochrome; Hypocotyl negative gravitropism; Endodermis starch granule; Brassinosteroid; non-cell autonomousy; 피토크롬; 배축음성굴지성; 내피녹말과립; 브라시노스테로이드; 세포자율성

URI
http://hdl.handle.net/10203/241844
Link
http://library.kaist.ac.kr/search/detail/view.do?bibCtrlNo=675718&flag=dissertation
Appears in Collection
BS-Theses_Ph.D.(박사논문)
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