Journal of Plant Biotechnology

The Korean Society of Plant Biotechnology (한국식물생명공학회)
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MACROPHYLLA/ROTUNDIFOLIA3 gene of Arabidopsis controls leaf index during leaf development

잎의 발달단계의 leaf index를 조절하는 애기장대 MACROPHYLLA/ROTUNDIFOLIA3 유전자

  • Jun, Sang-Eun (Department of Molecular Biotechnology, Dong-A University) ;
  • Chandrasekhar, Thummala (Department of Molecular Biotechnology, Dong-A University) ;
  • Cho, Kiu-Hyung (Department of Molecular Biotechnology, Dong-A University) ;
  • Yi, Young-Byung (Department of Molecular Biotechnology, Dong-A University) ;
  • Hyung, Nam-In (Department of Plant Science and Technology, Sangmyung University) ;
  • Nam, Jae-Sung (Department of Molecular Biotechnology, Dong-A University) ;
  • Kim, Gyung-Tae (Department of Molecular Biotechnology, Dong-A University)
  • 전상은 (동아대 생명자원과대학 분자생명공학과) ;
  • 투말라 찬드라쉐이커 (동아대 생명자원과대학 분자생명공학과) ;
  • 조규형 (동아대 생명자원과대학 분자생명공학과) ;
  • 이영병 (동아대 생명자원과대학 분자생명공학과) ;
  • 형남인 (상명대 산업대학 식물산업공학과) ;
  • 남재성 (동아대 생명자원과대학 분자생명공학과) ;
  • 김경태 (동아대 생명자원과대학 분자생명공학과)
  • Received : 2011.11.08
  • Accepted : 2011.11.22
  • Published : 2011.12.31
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Abstract

In plants, heteroblasty reflects the morphological adaptation during leaf development according to the external environmental condition and affects the final shape and size of organ. Among parameters displaying heteroblasty, leaf index is an important and typical one to represent the shape and size of simple leaves. Leaf index factor is eventually determined by cell proliferation and cell expansion in leaf blades. Although several regulators and their mechanisms controlling the cell division and cell expansion in leaf development have been studied, it does not fully provide a blueprint of organ formation and morphogenesis during environmental changes. To investigate genes and their mechanisms controlling leaf index during leaf development, we carried out molecular-genetic and physiological experiments using an Arabidopsis mutant. In this study, we identified macrophylla (mac) which had enlarged leaves. In detail, the mac mutant showed alteration in leaf index and cell expansion in direction of width and length, resulting in not only modification of leaf shape but also disruption of heteroblasty. Molecular-genetic studies indicated that mac mutant had point mutation in ROTUDIFOLIA3 (ROT3) gene involved in brassinosteroid biosynthesis and was an allele of rot3-1 mutant. We named it mac/rot3-5 mutant. The expression of ROT3 gene was controlled by negative feedback inhibition by the treatment of brassinosteroid hormone, suggesting that ROT3 gene was involved in brassinosteroid biosynthesis. In dark condition, in addition, the expression of ROT3 gene was up-regulated and mac/rot3-5 mutant showed lower response, compare to wild type in petiole elongation. This study suggests that ROT3 gene has an important role in control of leaf index during leaf expansion process for proper environmental adaptation, such as shade avoidance syndrome, via the control of brassinosteroid biosynthesis.

식물 잎의 발달과정에서 heteroblasty는 외부 환경에 대한 식물의 형태적 적응 방법을 매우 잘 반영하며 이에 따른 변화는 기관의 최종 형태와 크기에 영향을 미친다. Heteroblasty를 나타내는 인자 중에서 leaf index는 단엽식물의 잎의 최종 모양과 크기를 나타내는 대표적인 인자이다. Leaf index는 결국 잎몸에서의 세포 증식과 세포 신장의 두 요인에 의해 결정된다. 비록 세포의 증식과 신장을 조절하는 유전자와 조절 기작들이 연구되고 있으나 큰 청사진을 제시하기에는 아직 미흡하다. 본 연구에서는 발달과정 중 잎의 leaf index 조절에 관여하는 유전자를 밝히고 그 조절 기작을 알아내기 위하여 애기장대 돌연변이체를 이용한 분자유전학적, 생리학적인 실험을 수행하였다. 잎과 잎 세포가 커지는 돌연변이체인 macrophylla (mac)를 선발하여 잎의 확장과정과 leaf index의 이상으로 인해 잎 기관의 모양뿐 만 아니라 heteroblasty에 변화가 발생했다는 사실을 밝혀냈다. 또한 이 돌연변이체는 기존에 알려진 ROTUNDIFOLIA3 (ROT3) 유전자의 점 돌연변이에 의해 일어났다고 판명되었고 mac/rot3-5로 명명되었다. 브라시노스테로이드 처리로 인해 ROT3 유전자의 발현이 음성 되먹임 저해를 받는 것으로 보아 ROT3 유전자가 브라시노스테로이드 생합성에 관여함을 제시하였다. 또한 암상태에서 ROT3 유전자의 발현이 증가하며, mac/rot3-5 돌연변이체가 야생형보다 암반응이 약하게 나타났다. 이러한 분석 결과를 토대로 본 논문은 ROT3 유전자가 잎의 확장과정에서 잎의 leaf index 조절과 고유한 heteroblasty의 정립에 중요한 역할을 수행하며, 브라시노스테로이드 호르몬의 조절을 통하여 음지회피성과 같은 환경조절반응을 수행하고 있다는 새로운 사실을 제시하였다.

Keywords

References

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