Death by Necrosis: The Early Stages of Type 1 Diabetes

Background: The plant hormone auxin exerts many of its effects on growth and development by controlling transcription of downstream genes. The Arabidopsis gene AXR3/IAA17 encodes a member of the Aux/IAA family of auxin responsive transcriptional repressors. Semi-dominant mutations in AXR3 result in an increased amplitude of auxin responses due to hyperstabilisation of the encoded protein. The aim of this study was to identify novel genes involved in auxin signal transduction by screening for second site mutations that modify the axr3-1 gain-of-function phenotype. Results: We present the isolation of the partial suppressor of axr3-1 (pax1-1) mutant, which partially suppresses almost every aspect of the axr3-1 phenotype, and that of the weaker axr3-3 allele. axr31 protein turnover does not appear to be altered by pax1-1. However, expression of an AXR3::GUS reporter is reduced in a pax1-1 background, suggesting that PAX1 positively regulates AXR3 transcription. The pax1-1 mutation also affects the phenotypes conferred by stabilising mutations in other Aux/IAA proteins; however, the interactions are more complex than with axr3-1. Conclusion: We propose that PAX1 influences auxin response via its effects on AXR3 expression and that it regulates other Aux/IAAs secondarily. Background The phytohormone auxin is central to the regulation of plant growth and development. Processes controlled by auxin include apical dominance, adventitious root formation, tropic responses, vascular patterning and root hair development [1-6]. These diverse morphological events are brought about by changes in cell division, expansion and differentiation [7-9], and many of them are mediated by the ability of auxin to control gene expression. Several families of genes containing Auxin Response Elements (AuxREs) in their promoters, are rapidly transcriptionally upregulated as a primary response to auxin [10], including members of the Aux/IAA gene family. The Aux/IAA genes form a large multi-gene family found throughout the plant kingdom [11-14]. There are 29 members in Arabidopsis and their expression varies with respect to tissue specificity, auxin induction kinetics and Published: 12 April 2007 BMC Plant Biology 2007, 7:20 doi:10.1186/1471-2229-7-20 Received: 6 November 2006 Accepted: 12 April 2007 This article is available from: http://www.biomedcentral.com/1471-2229/7/20 © 2007 Tanimoto et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.