The transcription factor AtGRF5 and the transcription coactivator AN3 regulate cell proliferation in leaf primordia of Arabidopsis thaliana

Abstract

SummaryThe development of the flat morphology of leaf blades is dependent on the control of cell proliferation as well as cell expansion. Each process has a polarity with respect to the longitudinal and transverse axes of the leaf blade. However, only a few regulatory components of these processes have been identified to date. We have characterized two genes from Arabidopsis thaliana: ANGUSTIFOLIA3 (AN3), which encodes a homolog of the human transcription coactivator SYT, and GROWTH-REGULATING FACTOR5 (AtGRF5), which encodes a putative transcription factor. AN3 is identical to GRF-INTERACTING FACTOR1 (AtGIF1). The an3 and atgrf5 mutants exhibit narrow-leaf phenotypes due to decreases in cell number. Conversely, cell proliferation in leaf primordia is enhanced and leaves grow larger than normal when AN3 or AtGRF5 is overexpressed. Both genes are expressed in leaf primordia, and in the yeast two-hybrid assay, the gene products were found to interact with each other through their N-terminal domains. These results suggest that AN3 and AtGRF5 act together and are required for the development of appropriate leaf size and shape through the promotion and/or maintenance of cell proliferation activity in leaf primordia.

The Sink-Specific Plastidic Phosphate Transporter PHT4;2 Influences Starch Accumulation and Leaf Size in Arabidopsis

“…Overexpression of JAW1, which is involved in the regulation of jasmonate biosynthesis (Palatnik et al, 2003;Schommer et al, 2008), leads to the enlargement of only the first rosette leaves, and these have a characteristic uneven shape. Leaf enlargement is also restricted to the first few rosette leaves in lines overexpressing GRF5 and BRI1, a brassinosteroid receptor (Wang et al, 2001;Horiguchi et al, 2005), whereas overexpression of GA20OX1, an enzyme involved in GA synthesis (Huang et al, 1998), yields enlarged young but not older leaves.…”

The ArabidopsisGRF-INTERACTING FACTORGene Family Performs an Overlapping Function in Determining Organ Size as Well as Multiple Developmental Properties

“…The overlapping expression pattern and functional redundancy are in line with our previous biochemical studies showing that GIF2 proteins interact with GRF1 proteins as does GIF1 (Kim and Kende, 2004), raising the possibility that all three GIF proteins may participate in the formation of the functional transcriptional complex with GRF proteins in a combinatorial manner. However, not all GRFs may be in the complex to the same extent, because GIF1 interacted strongly with GRF5 and GRF9 but weakly with GRF4 (Horiguchi et al, 2005).…”

“…8; Kim et al, 2003;Horiguchi et al, 2005). It may be due to other factors limited in the mechanisms of organ size determination, and GIFs and GRFs are very likely to be limiting factors to each other.…”

“…8). Horiguchi et al (2005) have previously shown that overexpression of the GIF1/AN3 gene stimulates cell proliferation as well, leading to enlarged leaves by about 20%. These results led us to the conclusion that all of the GIF genes function redundantly as positive regulators of cell proliferation, thereby determining plant organ size.…”

“…Like the grf triple mutant, the gif1 single mutant showed narrow and small leaves as well as flower petals, which were caused by a reduction in cell numbers, indicating that GRF and GIF1 proteins form a functional complex involved in regulating cell proliferation and, thus, growth and shape of lateral organs (Kim and Kende, 2004). Horiguchi et al (2005) also confirmed the result by demonstrating that angustifolia3 (an3) mutations, which occurred at the GIF1 gene, and the grf5 mutation caused a reduction in cell numbers, leading to small and narrow lateral organs, while overexpression of GIF1/AN3 increased leaf size with normal shape.…”