Abstract
Rice varieties with suitable flour-making qualities are required to promote the rice processed-food industry and to boost rice consumption. A rice mutation, Namil(SA)-flo1, produces grains with floury endosperm. Overall, grains with low grain hardness, low starch damage, and fine particle size are more suitable for use in flour processing grains with waxy, dull endosperm with normal grain hardness and a high amylose content. In this study, fine mapping found a C to T single nucleotide polymorphism (SNP) in exon 2 of the gene encoding cytosolic pyruvate phosphate dikinase (cyOsPPDK). The SNP resulted in a change of serine to phenylalanine acid at amino acid position 101. The gene was named FLOURY ENDOSPERM 4-5 (FLO4-5). Co-segregation analysis with the developed cleaved amplified polymorphic sequence (CAPS) markers revealed co-segregation between the floury phenotype and the flo4-5. This CAPS marker could be applied directly for marker-assisted selection. Real-time RT-PCR experiments revealed that PPDK was expressed at considerably higher levels in the flo4-5 mutant than in the wild type during the grain filling stage. Plastid ADP-glucose pyrophosphorylase small subunit (AGPS2a and AGPS2b) and soluble starch synthase (SSIIb and SSIIc) also exhibited enhanced expression in the flo4-5 mutant.
Highlights
Rice (Oryza sativa L.) is a staple food for more than half the world’s population; improving yield and grain quality is of great importance
Tiller number, and spikelets per panicle did not differ significantly between the wild type and Namil(SA)-flo1 mutant, but ripened grains percentage (RGP) was lower in Namil(SA)-flo1 than in the wild type (Table 1)
Our results suggest that enhanced synthesis of ADP-Glc in the rice seed endosperm may increase seed number
Summary
Rice (Oryza sativa L.) is a staple food for more than half the world’s population; improving yield and grain quality is of great importance. Grain yield can be increased considerably through the use of hybrid rice strains, but the grain quality of these varieties does not fully satisfy customer demands [1]. Grain quality improvement is the current focus of many rice geneticists worldwide. Cultivars with a range of different grain qualities are desirable for specific production or medicinal purposes. Starch, which is the major storage carbohydrate in rice grains, constitutes approximately 90% of a rice grain, of which approximately 18% is amylose and 82% is amylopectin.
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