Photo: Courtesy of M. Matsuoka, Reprinted with permission from Nature ©2001
 A COMPARISON: The effect of a mutant gibberellin-biosynthesis gene is shown in rice plants; on the left, wild type; on the right, IR8 (sd1).

During the summer of 1997, two research groups succeeded in bringing closure to a classic tale in genetics. After 131 years, they identified one of Mendel's pea genes at the molecular level. The gene, called Le, controls stem length--plants with defective copies are shorter than normal. Characterized in both pea and Arabidopsis, the gene encodes an enzyme called gibberellin 3b-hydroxylase, which converts two precursors of the growth regulator gibberellin into active forms, including gibberellin 1.1,2 Le was the second of Mendel's genes to be identified. Re-searchers pulled out the first--for a starch-branching enzyme that in defective form causes the wrinkled seed trait--12 years ago.3

Now a gene called GA20ox-2...

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