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Erect leaves caused by brassinosteroid deficiency increase biomass production and grain yield in rice


New cultivars with very erect leaves, which increase light capture for photosynthesis and nitrogen storage for grain filling, may have increased grain yields1. Here we show that the erect leaf phenotype of a rice brassinosteroid–deficient mutant, osdwarf4-1, is associated with enhanced grain yields under conditions of dense planting, even without extra fertilizer. Molecular and biochemical studies reveal that two different cytochrome P450s, CYP90B2/OsDWARF4 and CYP724B1/D11, function redundantly in C-22 hydroxylation, the rate-limiting step of brassinosteroid biosynthesis. Therefore, despite the central role of brassinosteroids in plant growth and development, mutation of OsDWARF4 alone causes only limited defects in brassinosteroid biosynthesis and plant morphology. These results suggest that regulated genetic modulation of brassinosteroid biosynthesis can improve crops without the negative environmental effects of fertilizers.

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Figure 1: Molecular characterization of OsDWARF4 and OsDWARF4L1/D11.
Figure 2: Phenotypes of rice mutants defective in brassinosteroid biosynthesis.
Figure 3: Characterization of a field-grown osdwarf4-1 mutant.


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T.S. was supported by a grant from the Ministry of Agriculture, Forestry and Fisheries of Japan (Rice Genome Project IP-1010) and a Grant-in-Aid for Young Scientists (B) from the Ministry of Education, Culture, Sports, Science and Technology (MEXT). M.U.-T. and H.K. were supported by a grant from the Program for Promotion of Basic Research Activities for Innovation of Biosciences, and M. Matsuoka was supported by a Grant-in-Aid for Centers of Excellence from MEXT. We thank M. Sekimoto, H. Hayashi, N. Kato, K. Izumi and K. Yatsuda for their technical assistance.

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Correspondence to Tomoaki Sakamoto.

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The authors declare no competing financial interests.

Supplementary information

Supplementary Table 1

Metabolism of recombinanat CYP724B1/D11 protein. (PDF 47 kb)

Supplementary Table 2

Morphological characterization of wild-type and osdwarf4-1 mutant plants. (PDF 74 kb)

Supplementary Table 3

Accession numbers used in this paper. (PDF 67 kb)

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Sakamoto, T., Morinaka, Y., Ohnishi, T. et al. Erect leaves caused by brassinosteroid deficiency increase biomass production and grain yield in rice. Nat Biotechnol 24, 105–109 (2006).

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