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A role for phospholipase A in auxin‐regulated gene expression
Author(s) -
Scherer Günther F.E.,
Zahn Marc,
Callis Judy,
Jones Alan M.
Publication year - 2007
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/j.febslet.2007.07.059
Subject(s) - auxin , arabidopsis , biology , phospholipase , phospholipase c , gene expression , phosphoinositide phospholipase c , biochemistry , phospholipase a , microbiology and biotechnology , signal transduction , gene , phospholipase a2 , mutant , enzyme
Auxin increases phospholipase A 2 activity within 2 min (Paul, R., Holk, A. and Scherer, G.F.E. (1998) Fatty acids and lysophospholipids as potential second messengers in auxin action. Rapid activation of phospholipase A 2 activity by auxin in suspension‐cultured parsley and soybean cells. Plant J. 16, 601–611) and the phospholipase A inhibitors, ETYA and HELSS, inhibit elongation growth of etiolated Arabidopsis hypoctyls (Holk, A., Rietz, S., Zahn, M., Quader, H. and Scherer, G.F.E. (2002) Molecular identification of cytosolic, patatin‐related phospholipases A from Arabidopsis with potential functions in plant signal transduction. Plant Physiol. 130, 90–101). To identify the mode of action, rapid auxin‐regulated gene expression was tested for sensitivity to these PLA 2 inhibitors using seedlings expressing β‐glucuronidase (GUS) under the control of the synthetic auxin‐responsive promoter DR5. ETYA and HELSS inhibited the auxin‐induced increases in GUS activity, the steady‐state level of the corresponding GUS mRNA and the mRNAs encoded by four other auxin‐induced genes, IAA1, IAA5, IAA19 and ARF19. Factors that bind to the auxin response elements of the DR5 promoter and thereby regulate gene expression are regulated by a set of proteins such as Aux/IAA1 whose abundances are, in part, under control of E3 ubiquitin ligase SCF complexes. To investigate this mechanism further, the effect of ETYA on Aux/IAA1 degradation rate was examined using seedlings expressing Aux/IAA1:luciferase fusion proteins. In the presence of cycloheximide and excluding synthesis of IAA1:luciferase, ETYA had no apparent effect on degradation rates of IAA1, either with or without exogenous auxin. Therefore, the E3 ubiquitin ligase SCF TIR1 complex is an unlikely direct target of the PLA inhibitor. When cycloheximide was omitted, however, the inhibitors ETYA and HELSS blocked a sustained auxin‐induced decrease in its steady‐state level, indicating an unknown target capable to regulate Aux/IAA protein levels and, hence, transcription.