Reference "Semidwarf (sd-1), "green revolution" rice, contains a defective gibberellin 20-oxidase gene"

Reference ID

6944

Title

Semidwarf (sd-1), "green revolution" rice, contains a defective gibberellin 20-oxidase gene

Source

Proceedings of the National Academy of Sciences of the United States of America, 2002, vol. 99, pp. 9043-9048

Authors (3)

Spielmeyer-W	Ellis-M-H
Chandler-P-M

Abstract

The introduction of semidwarf rice (Oryza sativa L.) led to record yield
increases throughout Asia in the 1960s. The major semidwarfing allele, sd-1, is
still extensively used in modern rice cultivars. The phenotype of sd-1 is
consistent with dwarfism that results from a deficiency in gibberellin (GA)
plant growth hormones. We propose that the semidwarf (sd-1) phenotype is the
result of a deficiency of active GAs in the elongating stem arising from a
defective 20-oxidase GA biosynthetic enzyme. Sequence data from the rice genome
was combined with previous mapping studies to locate a putative GA 20-oxidase
gene (Os20ox2) at the predicted map location of sd-1 on chromosome 1. Two
independent sd-1 alleles contained alterations within Os20ox2: a deletion of 280
bp within the coding region of Os20ox2 was predicted to encode a nonfunctional
protein in an indica type semidwarf (Doongara), whereas a substitution in an
amino acid residue (Leu-266) that is highly conserved among dioxygenases could
explain loss of function of Os20ox2 in a japonica semidwarf (Calrose76). The
quantification of GAs in elongating stems by GC-MS showed that the initial
substrate of GA 20-oxidase activity (GA53) accumulated, whereas the content of
the major product (GA20) and of bioactive GA1 was lower in semidwarf compared
with tall lines. We propose that the Os20ox2 gene corresponds to the sd-1 locus.