RT Journal Article SR Electronic T1 The Pseudo-Response Regulator Ppd-H1 Provides Adaptation to Photoperiod in Barley JF Science JO Science FD American Association for the Advancement of Science SP 1031 OP 1034 DO 10.1126/science.1117619 VO 310 IS 5750 A1 Turner, Adrian A1 Beales, James A1 Faure, Sébastien A1 Dunford, Roy P. A1 Laurie, David A. YR 2005 UL http://science.sciencemag.org/content/310/5750/1031.abstract AB Plants commonly use photoperiod (day length) to control the timing of flowering during the year, and variation in photoperiod response has been selected in many crops to provide adaptation to different environments and farming practices. Positional cloning identified Ppd-H1, the major determinant of barley photoperiod response, as a pseudo-response regulator, a class of genes involved in circadian clock function. Reduced photoperiod responsiveness of the ppd-H1 mutant, which is highly advantageous in spring-sown varieties, is explained by altered circadian expression of the photoperiod pathway gene CONSTANS and reduced expression of its downstream target, FT, a key regulator of flowering.