Author(s)

Tomoaki Sakamoto, Yoichi Morinaka, Hidemi Kitano, Shozo Fujioka

Bioscience and Biotechnology Center, Nagoya University, Nagoya, Japan.
Faculty of Bioresources and Environmental Sciences, Ishikawa Prefectural University, Nonoichi, Japan.
RIKEN Advanced Science Institute, Wako, Japan.

ebisu dwarf (d2) is a mutant caused by mutation in a rice brassinosteroid biosynthetic enzyme gene, CYP90D2/D2, thereby conferring a brassinosteroid-deficient dwarf phenotype. Three newly isolated d2 alleles derived from a Nippon- bare mutant library (d2-3, d2-4, and d2-6) produced more severe dwarf phenotypes than the previously characterized null allele from a Taichung 65 mutant library, d2-1. Linkage analysis and a complementation test clearly indicated that the mutant phenotypes in d2-6 were caused by defects in CYP90D2/D2, and exogenous treatment with brassinolide, a bioactive brassinosteroid, rescued the dwarf phenotype of three Nipponbare-derived d2 mutants. However, the content of endogenous bioactive brassinosteroid, castasterone, and the expression of brassinosteroid-response genes indicated that partial suppression of the brassinosteroid response in addition to a brassinosteroid deficiency has occurred in the Nipponbare-derived d2 mutants. Based on these results, we discuss the possibility that wild-type Nipponbare has some defects in an unknown factor or factors related to the brassinosteroid response in rice.

Brassinosteroids; Brassinosteroid Biosynthetic Enzymes; Brassinosteroid Sensitivity;Cytochrome P450 Monooxygenase; Mutant Allele; Rice

Sakamoto, T. , Morinaka, Y. , Kitano, H. and Fujioka, S. (2012) New Alleles of Rice ebisu dwarf (d2) Mutant Show both Brassinosteroid-Deficient and -Insensitive Phenotypes. American Journal of Plant Sciences, 3, 1699-1707. doi: 10.4236/ajps.2012.312208.