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First published online October 12, 2006
doi: 10.1242/10.1242/dev.02604

Development 133, 4305-4314 (2006)
Published by The Company of Biologists 2006
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LONGIFOLIA1 and LONGIFOLIA2, two homologous genes, regulate longitudinal cell elongation in Arabidopsis

Young Koung Lee1,*, Gyung-Tae Kim2,3,*, In-Jung Kim4, Jeongmoo Park1, Sang-Soo Kwak5, Giltsu Choi1,{dagger} and Won-Il Chung1,{dagger}

1 Department of Biological Sciences, KAIST, Daejeon 305-701, Korea.
2 Division of Molecular Biotechnology, Dong-A University, Busan 604-714, Korea.
3 Environmental Biotechnology Research Center, Gyeongsang National University, Jinju 660-701, Korea.
4 Faculty of Biotechnology, College of Applied Life Sciences, Cheju National University, Jeju 690-756, Korea.
5 Laboratory of Environmental Biotechnology, Korea Research Institute of Bioscience and Biotechnology (KRIBB), 52 Eoen-dong, Yuseong-gu, Daejeon, 305-806, Korea.

{dagger} Authors for correspondence (e-mail: gchoi{at}kaist.ac.kr; wichung{at}kaist.ac.kr)

Accepted 30 August 2006

Plants have diversified their leaf morphologies to adapt to diverse ecological niches. The molecular components responsible for regulating leaf morphology, however, have not been fully elucidated. By screening Arabidopsis activation-tagging lines, we identified a dominant mutant, which we designated longifolia1-1D (lng1-1D). lng1-1D plants were characterized by long petioles, narrow but extremely long leaf blades with serrated margins, elongated floral organs, and elongated siliques. The elongated leaves of the mutant were due to increased polar cell elongation rather than increased cell proliferation. Molecular characterization revealed that this phenotype was caused by overexpression of the novel gene LNG1, which was found to have a homolog, LNG2,in Arabidopsis. To further examine the role of the LNG genes, we characterized lng1 and lng2 loss-of-function mutant lines. In contrast to the elongated leaves of lng1-1D plants, the lng1 and lng2 mutants showed slightly decreased leaf length. Furthermore, the lng1-3 lng2-1 double mutant showed further decreased leaf length associated with less longitudinal polar cell elongation. The leaf widths in lng1-3 lng2-1 mutant plants were similar to those in wild type, implying that the role of LNG1 and LNG2 on polar cell elongation is similar to that of ROTUNDIFOLIA3 (ROT3). However, analysis of a lng1-3 lng2-1 rot3-1 triple mutant and of a lng1-1D rot3-1 double mutant indicated that LNG1 and LNG2 promote longitudinal cell elongation independently of ROT3. Taken together, these findings indicate that LNG1 and LNG2 are new components that regulate leaf morphology by positively promoting longitudinal polar cell elongation independently of ROT3 in Arabidopsis.

Key words: Arabidopsis, Polar cell elongation, Leaf development, LONGIFOLIA






© The Company of Biologists Ltd 2006