DFL1, an auxin-responsive GH3 gene homologue, negatively regulates shoot cell elongation and lateral root formation, and positively regulates the light response of hypocotyl length

Abstract

A novel dominant mutant designated 'dwarf in light 1' (dfl1-D) was isolated from screening around 1200 Arabidopsis activation-tagged lines. dfl1-D has a shorter hypocotyl under blue, red and far-red light, but not in darkness. Inhibition of cell elongation in shoots caused an exaggerated dwarf phenotype in the adult plant. The lateral root growth of dfl1-D was inhibited without any reduction of primary root length. The genomic DNA adjacent to the right border of T-DNA was cloned by plasmid rescue. The rescued genomic DNA contained a gene encoding a GH3 homologue. The transcript was highly accumulated in the dfl1-D. The dfl1-D phenotype was confirmed by over-expression of the gene in the wild-type plant. The dfl1-D showed resistance to exogenous auxin treatment. Moreover, over-expression of antisense DFL1 resulted in larger shoots and an increase in the number of lateral roots. These results indicate that the gene product of DFL1 is involved in auxin signal transduction, and inhibits shoot and hypocotyl cell elongation and lateral root cell differentiation in light.

Research progresses on GH3s, one family of primary auxin-responsive genes

“…Group I includes AtGH3-11/FIN219/JAR1 and AtGH3-10/DFL2 (Hsieh et al 2000;Staswick et al 2002;Takase et al 2003). Group II consists of AtGH3-2/ YDK1, AtGH3-5/AtGH3a/WES1, AtGH3-9, AtGH3-6/ DFL1 and four other members (Nakazawa et al 2001;Takase et al 2004;Tanaka et al 2002). Group III is composed of AtGH3-12/PBS3/GDG1 and nine other members (Jagadeeswaran et al 2007;Nobuta et al 2007).…”

“…So far, mutants of seven Arabidopsis GH3 genes were identified via morphological screening and they displayed distinct but interrelated phenotypes (Table 2; Hsieh et al 2000;Khan and Stone 2007;Nakazawa et al 2001;Staswick et al 2002;Takase et al 2004;Takase et al 2003;Tanaka et al 2002;Zhang et al 2007). AtGH3-11, one Group I gene, is induced by auxin and encodes a protein that specifically adenylates JA but not IAA or other hormones in vitro (Staswick and Tiryaki 2004;Staswick et al 2002).…”

“…Further analyses on YDK1 and DFL1 expression have shown that YDK1 is inhibited by blue and far-red light, but DFL1 is not influenced by light. Therefore DFL1 protein should function with one or more light-induced partner (s) in regulating hypocotyls elongation (Nakazawa et al 2001;Takase et al 2004).…”

“…Longer hypocotyl in red light Takase et al (2003) AtGH3-11 fin219 Longer hypocotyl in far-red Hsieh et al (2000) jar1-1 Insensitivity to MeJA in root growth Staswick et al (2002) II AtGH3-2 ydk1-D Shorter hypocotyl in light and darkness Takase et al (2004) AtGH3-5 wes1-D Shorter hypocotyl in red light; reduced growth, small plant organs and enhanced stress adaptation Park et al (2007a, b) gh3.5-1D Smaller curly rosette leaves, shortened primary roots and reduced lateral roots Zhang et al (2007) AtGH3-6 dfl1-D Shorter hypocotyl in light Nakazawa et al (2001) AtGH3-9 gh3.9-1 Longer primary root Khan and Stone (2007) III AtGH3-12 pbs3-1 Enhanced susceptibility to avirulent and virulent P. syringae strains Nobuta et al (2007) gdg1 Jagadeeswaran et al (2007) Plant Growth Regul (2008) 56:225-232 229 gh3.9-1 shows moderately JA resistance, indicating that AtGH3.9 is likely to be a juncture between auxin and JA response pathway (Khan and Stone 2007).…”

Transcriptomic evaluation of the enhanced plant growth-inhibitory activity caused by derivatization of <i>cis</i>-cinnamic acid

“…The upregulation of GH3 genes might contribute to seedling growth regulation because some gain-of-function mutation studies of GH3 genes caused negative effects on plant growth. 18,19) No additional distinguishable gene responses between treatments with 1 and 2 were observed.…”