transcriptional coactivator, AtGIF1, is involved in regulating leaf growth and morphology in Arabidopsis

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 101; no. 36; pp. 13374 - 13379
• Main Authors: Kim J.H, Kende, H
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 07.09.2004; National Acad Sciences
• Subjects: Arabidopsis - anatomy & histology; Arabidopsis - growth & development; Arabidopsis Proteins - physiology; Arabidopsis thaliana; Base Sequence; Biological Sciences; Biology; Cell Count; Cell Division; Cell growth; Epidermal cells; Flowers & plants; Genotype & phenotype; Leaves; Molecular Sequence Data; Mutants; Mutation; Petals; Phenotypes; Physical growth; Plant growth regulators; Plant Leaves - anatomy & histology; Plant Leaves - growth & development; Plants; Plants, Genetically Modified; Proteins; Ribonucleic acid; RNA; Trans-Activators - physiology; Transactivation; Transgenic plants; Yeasts
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0405450101

Previously, we described the AtGRF [Arabidopsis thaliana growth-regulating factor (GRF)] gene family, which encodes putative transcription factors that play a regulatory role in growth and development of leaves and cotyledons. We demonstrate here that the C-terminal region of GRF proteins has transactivation activity. In search of partner proteins for GRF1, we identified another gene family, GRF-interacting factor (GIF), which comprises three members. Sequence and molecular analysis showed that GIF1 is a functional homolog of the human SYT transcription coactivator. We found that the N-terminal region of GIF1 protein was involved in the interaction with GRF1. To understand the biological function of GIF1, we isolated a loss-of-function mutant of GIF1 and prepared transgenic plants subject to GIF1-specific RNA interference. Like grf mutants, the gif1 mutant and transgenic plants developed narrower leaves and petals than did wild-type plants, and combinations of gif1 and grf mutations showed a cooperative effect. The narrow leaf phenotype of gif1, as well as that of the grf triple mutant, was caused by a reduction in cell numbers along the leaf-width axis. We propose that GRF1 and GIF1 act as transcription activator and coactivator, respectively, and that they are part of a complex involved in regulating the growth and shape of leaves and petals.