TY - JOUR
T1 - Arabidopsis thaliana GH3.9 influences primary root growth
AU - Khan, Sadaf
AU - Stone, Julie M.
N1 - Funding Information:
Acknowledgments Vector pFGC5941 was kindly provided by Rich Jorgenson (University of Arizona, Tucson, AZ). We would like to thank Paul Staswick, Jane Murfett, John Markwell and members of the Stone laboratory for critical discussions and review of the manuscript. We thank Christian Elowsky for his superb help with the microscopy/photography. This work was supported in part by a National Science Foundation grant to JMS (NSF IBN#0221925). A contribution of the University of Nebraska, Agricultural Research Division, Lincoln, NE 68583.
PY - 2007/6
Y1 - 2007/6
N2 - Auxins regulate a complex signal transduction network to direct plant development. Auxin-responsive genes fit into three major classes: the so-called auxin/indole-3-acetic acid (Aux/IAA), the GH3, and the small auxin-up RNA (SAUR) gene families. The 20-member Arabidopsis thaliana GH3 gene family has been subdivided into three groups. In vitro studies have shown that most Group II members function as IAA-amido synthetases to conjugate amino acids to the plant hormone auxin. Here we report the role of a previously uncharacterized GH3 gene family member, GH3.9, in root growth. Unlike most other Group II family members, GH3.9 expression was repressed by low concentrations of exogenous IAA in seedlings. Transgenic plants harboring a GH3.9 promoter::reporter gene construct indicate that GH3.9 is expressed in the root-hypocotyl junction, leaves and the shoot apical meristem of young seedlings, in mature embryos, and in the root vascular tissue. Expression was also observed in lateral root tips when seedlings were treated with exogenous IAA. Inverse PCR was used to identify an activation tagged T-DNA insertion in chromosome 2 near the 5′UTR region of At2g47750 (GH3.9). Plants homozygous for the T-DNA insertion (gh3.9-1 mutants) had reduced GH3.9 expression, no obvious effects on apical dominance or leaf morphology, greater primary root length, and increased sensitivity to indole-3-acetic acid (IAA)-mediated root growth inhibition. Additional T-DNA insertion alleles and transgenic plants with reduced GH3.9 transcript levels due to RNA-interference (RNAi) also showed these same phenotypes. Our results provide new information on the function of GH3.9 in roots where it is likely to control auxin activity through amino acid conjugation.
AB - Auxins regulate a complex signal transduction network to direct plant development. Auxin-responsive genes fit into three major classes: the so-called auxin/indole-3-acetic acid (Aux/IAA), the GH3, and the small auxin-up RNA (SAUR) gene families. The 20-member Arabidopsis thaliana GH3 gene family has been subdivided into three groups. In vitro studies have shown that most Group II members function as IAA-amido synthetases to conjugate amino acids to the plant hormone auxin. Here we report the role of a previously uncharacterized GH3 gene family member, GH3.9, in root growth. Unlike most other Group II family members, GH3.9 expression was repressed by low concentrations of exogenous IAA in seedlings. Transgenic plants harboring a GH3.9 promoter::reporter gene construct indicate that GH3.9 is expressed in the root-hypocotyl junction, leaves and the shoot apical meristem of young seedlings, in mature embryos, and in the root vascular tissue. Expression was also observed in lateral root tips when seedlings were treated with exogenous IAA. Inverse PCR was used to identify an activation tagged T-DNA insertion in chromosome 2 near the 5′UTR region of At2g47750 (GH3.9). Plants homozygous for the T-DNA insertion (gh3.9-1 mutants) had reduced GH3.9 expression, no obvious effects on apical dominance or leaf morphology, greater primary root length, and increased sensitivity to indole-3-acetic acid (IAA)-mediated root growth inhibition. Additional T-DNA insertion alleles and transgenic plants with reduced GH3.9 transcript levels due to RNA-interference (RNAi) also showed these same phenotypes. Our results provide new information on the function of GH3.9 in roots where it is likely to control auxin activity through amino acid conjugation.
KW - Auxin
KW - Plant hormones
KW - Primary root growth
KW - T-DNA insertion mutant
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U2 - 10.1007/s00425-006-0462-2
DO - 10.1007/s00425-006-0462-2
M3 - Article
C2 - 17216483
AN - SCOPUS:34248549188
VL - 226
SP - 21
EP - 34
JO - Planta
JF - Planta
SN - 0032-0935
IS - 1
ER -