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The auxin transport inhibitor response 3 ( tir3 ) allele of BIG and auxin transport inhibitors affect the gibberellin status of Arabidopsis
Author(s) -
DesgagnéPenix Isabel,
Eakanunkul Suntara,
Coles Jeremy P.,
Phillips Andrew L.,
Hedden Peter,
Sponsel Valerie M.
Publication year - 2005
Publication title -
the plant journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.058
H-Index - 269
eISSN - 1365-313X
pISSN - 0960-7412
DOI - 10.1111/j.1365-313x.2004.02287.x
Subject(s) - paclobutrazol , auxin , arabidopsis , gibberellin , gene , mutant , phenotype , polar auxin transport , shade avoidance , locus (genetics) , biology , microbiology and biotechnology , biochemistry , chemistry , genetics , botany
Summary The Arabidopsis gene BIG (formerly DOC1 / TIR3 / UMB1 / ASA1 ) is known to encode a huge calossin‐like protein that is required for polar auxin transport (PAT). Mutations at this locus, in addition to reducing PAT, can alter the sensitivity of plants to several hormones and light. The tir3‐1 allele of BIG reduces the response of plants to application of the gibberellin (GA) precursors ent ‐kaurenoic acid and GA 12 and its semidwarf phenotype is partially reversed by C 19 ‐GAs. The effects of auxin transport inhibitors (ATIs) on GA 20‐oxidation was examined in wild‐type and tir3‐1 seedlings. 1‐ N ‐naphthylphthalamic acid (NPA) and triiodobenzoic acid lead to overexpression of the GA‐biosynthetic gene AtGA20ox1 comparable in magnitude to the overexpression observed in seedlings treated with paclobutrazol, a GA biosynthesis inhibitor. In contrast to that of AtGA20ox1 , overexpression of AtGA20ox2 is pronounced only in paclobutrazol‐treated Col and L er , and is less in tir3‐1 and in all NPA‐treated seedlings. Thus the effects of BIG and ATIs on the expression of genes encoding GA 20‐oxidases are complex, and suggest that at least in some tissues ATIs, directly or indirectly, may reduce the level of bioactive GA and/or alter GA signal transduction.