First published online February 5, 2004; 10.1104/pp.103.031666
Plant Physiology 134:694-705 (2004)
© 2004 American Society of Plant Biologists
DEVELOPMENT AND HORMONE ACTION
The gar2 and rga Alleles Increase the Growth of Gibberellin-Deficient Pollen Tubes in Arabidopsis1
Stephen M. Swain*,
Andrea J. Muller and
Davinder P. Singh
Commonwealth Scientific and Industrial Research Organization Plant Industry, Private Mail Bag, Merbein, Victoria 3505, Australia (S.M.S., D.P.S.); and Department of Agricultural Science, La Trobe University, Bundoora, Victoria 3086, Australia (A.J.M.)
Ectopic expression in Arabidopsis of a pea (Pisum sativum) cDNA (2ox2) encoding a gibberellin (GA) 2-oxidase (PsGA2ox2), involved in the deactivation of biologically active GAs, has been used to establish a role for GAs in promoting pollen tube growth. One line, 35S:2ox2/28c, when homozygous for the transgene, exhibits a novel small fruit phenotype. The 28c transgene reduces pollen tube growth, and this results in a reduced number of fertilized seeds that are only present at the end of the silique nearest the stigma. To confirm that the 28c pollen tube phenotype is due to sense expression of the 2ox2 mRNA, a "hairpin" RNA interface silencing construct, designed to silence 2ox2 expression, has been used to restore pollen tube growth and fruit development. The interaction between 28c and other mutants with increased GA response has also been examined to provide further evidence that GAs play an important role in pollen tube growth. Based on the ability of mutant alleles to suppress the 35S:2ox2/28c phenotype, we define new roles for the gar2-1 and rga alleles in GA signaling during pollen tube elongation in addition to their previously established roles in vegetative tissues. In contrast to the constitutive GA response observed in internodes and leaves lacking RGA and GAI, the rga-2 gai-d5 mutant combination is only a partial suppressor of the 28c phenotype. Because the dominant dwarfing gai-1 allele reduces GA response in vegetative tissues, its effect on plant fertility has been examined. Although gai-1 reduces seed set, this appears to reflect defects in reproductive development other than pollen tube function. Finally, we show that the genetic background (Landsberg erecta or Columbia) modifies the 28c phenotype and that this effect is not due to the ER/er difference between these two ecotypes.
Article, publication date, and citation information can be found at www.plantphysiol.org/cgi/doi/10.1104/pp.103.031666.
1 This work supported in part by Horticulture Australia Ltd. as part of the Aushort gene discovery project.
* Corresponding author; e-mail Steve.Swain{at}csiro.au; fax 61–3–5051–3111.
Received August 10, 2003;
returned for revision September 1, 2003;
accepted November 22, 2003.
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