Molecular Info®

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Light and Brassinosteroid Signals Are Integrated via a Dark-Induced Small G Protein in Etiolated Seedling Growth Jeong-Gu Kang, Ju Yun, Dae-Hwan Kim, Kyung-Sook Chung, Shozo Fujioka, Jeong-Il Kim, Hye-Won Dae, Shigeo Yoshida, Suguru Takatsuto, Pill-Soon Song, and Chung-Mo Park Cell, Vol 105, 625-636, June 2001 A dark-induced small G protein, pea Pra2, regulates a variant cytochrome P450 that catalyzes C-2 hydroxylation in brassinosteroid biosynthesis. The cytochrome P450 is dark-induced and predominantly expressed in the rapidly elongating zone of etiolated pea epicotyls, where Pra2 is also most abundant. Transgenic plants with reduced Pra2 exhibit a dark-specific dwarfism, which is completely rescued by exogenous brassinolide. Overexpression of the cytochrome P450 results in enhanced hypocotyl growth even in the light, which phenocopies the etiolated hypocotyls. Pra2 and its orthologs are likely molecular mediators for the cross-talk between light and brassinosteroids in the etiolation process in plants.