Journal Article

Strigolactones Negatively Regulate Mesocotyl Elongation in Rice during Germination and Growth in Darkness

Zhongyuan Hu, Haifang Yan, Jinghua Yang, Shinjiro Yamaguchi, Masahiko Maekawa, Itsuro Takamure, Nobuhiro Tsutsumi, Junko Kyozuka and Mikio Nakazono

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 51, issue 7, pages 1136-1142
Published in print July 2010 | ISSN: 0032-0781
Published online May 2010 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/pcp/pcq075

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Strigolactones (SLs) are newly discovered plant hormones that regulate plant growth and development including shoot branching. They also stimulate symbiosis with arbuscular mycorrhizal fungi. Rice has at least three genes that are involved in SL synthesis (D10, D17/HTD1 and D27) and at least two genes that are involved in SL signaling (D3) and SL signaling or downstream metabolism (D14/D88/HTD2). We observed that mesocotyl elongation in darkness was greater in rice mutants defective in these genes than in the wild type. Exogenous application of a synthetic SL analog, GR24, rescued the phenotype of mesocotyl elongation in the SL-deficient mutants, d10-1, d17-1 and d27-1, in a dose-dependent manner, but did not affect mesocotyl lengths of the SL-insensitive mutants, d3-1 and d14-1. No significant differences in cell length were found between the d mutants and the wild type, except for some cells on the lower half of the d3-1 mesocotyl that were shortened. On the other hand, the number of cells in the mesocotyls was 3- to 6-fold greater in the d mutants than in the wild type. Treatment with GR24 reduced the number of cells in the d10-1 mesocotyl to the wild-type level, but did not affect the number of cells in the d3-1 and d14-1 mesocotyls. These findings indicate that SLs negatively regulate cell division, but not cell elongation, in the mesocotyl during germination and growth of rice in darkness.

Keywords: Cell division; dwarf mutants; Mesocotyl; Rice; Strigolactones

Journal Article.  3486 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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