*Article* **A New SNP in Rice Gene Encoding PyruvatePhosphate Dikinase (PPDK) Associated withFloury Endosperm**

**Heng Wang 1,2,**†**, Tae-Ho Ham 3,**†**, Da-Eun Im 1, San Mar Lar 1, Seong-Gyu Jang 1, Joohyun Lee 3, Youngjun Mo 4, Ji-Ung Jeung 4, Sun Tae Kim 1 and Soon-Wook Kwon 1,\***


† These authors contributed equally.

Received: 20 March 2020; Accepted: 22 April 2020; Published: 24 April 2020

**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 (cy*OsPPDK*). 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.

**Keywords:** *Oryza sativa* L.; PPDK; *flo4-5*; floury endosperm
