'Green revolution' genes encode mutant gibberellin response modulators

World wheat grain yields increased substantially in the 1960s and 1970s bec ause farmers rapidly adopted the new varieties and cultivation methods of t he so-called 'green revolution(1-4). The new varieties are shorter, increas e grain yield at the expense of straw biomass, and are more resistant to da mage by wind and rain(3,4). These wheats are short because they respond abn ormally to the plant growth hormone gibberellin, This reduced response to g ibberellin is conferred by mutant dwarfing alleles at one of two Reduced he ight-1 (Rht-B1 and Rht-D1) loci(4,5), Here we show that Rht-B1/Rht-D1 and m aize dwarf-8 (d8)(6,7) are orthologues of the Arabidopsis Gibberellin Insen sitive (GAI) gene(8,9). These genes encode proteins that resemble nuclear t ranscription factors and contain an SH2-like(10) domain, indicating that ph osphotyrosine may participate in gibberellin signalling. Six different orth ologous dwarfing mutant alleles encode proteins that are altered in a conse rved amino-terminal gibberellin signalling domain, Transgenic rice plants c ontaining a mutant GAI allele give reduced responses to gibberellin and are dwarfed, indicating that mutant GAI orthologues could be used to increase yield in a wide range of crop species.