Reference "Morphological alteration caused by brassinosteroid insensitivity increases the biomass and grain production of rice"

Reference ID

11406

Title

Morphological alteration caused by brassinosteroid insensitivity increases the biomass and grain production of rice

Source

Plant physiology, 2006, vol. 141, pp. 924-931

Authors (7)

Morinaka-Y	Sakamoto-T
Inukai-Y	Agetsuma-M
Kitano-H	Ashikari-M
Matsuoka-M

Abstract

The rice (Oryza sativa) dwarf mutant d61 phenotype is caused by loss of function
of a rice BRASSINOSTEROID INSENSITIVE1 ortholog, OsBRI1. We have identified nine
d61 alleles, the weakest of which, d61-7, confers agronomically important traits
such as semidwarf stature and erect leaves. Because erect-leaf habit is
considered to increase light capture for photosynthesis, we compared the biomass
and grain production of wild-type and d61-7 rice. The biomass of wild type was
38% higher than that of d61-7 at harvest under conventional planting density
because of the dwarfism of d61-7. However, the biomass of d61-7 was 35% higher
than that of wild type at high planting density. The grain yield of wild type
reached a maximum at middensity, but the yield of d61-7 continued to increase
with planting density. These results indicate that d61-7 produces biomass more
effectively than wild type, and consequently more effectively assimilates the
biomass in reproductive organ development at high planting density. However, the
small grain size of d61-7 counters any increase in grain yield, leading to the
same grain yield as that of wild type even at high density. We therefore
produced transgenic rice with partial suppression of endogenous OsBRI1
expression to obtain the erect-leaf phenotype without grain changes. The
estimated grain yield of these transformants was about 30% higher than that of
wild type at high density. These results demonstrate the feasibility of
generating erect-leaf plants by modifying the expression of the brassinosteroid
receptor gene in transgenic rice plants.