FLOURY ENDOSPERM6 encodes a CBM48 domain-containing protein involved in compound granule formation and starch synthesis in rice endosperm.
Starch is the most widespread form of energy storage in the plant kingdom. Although many enzymes and related factors have been identified for starch biosynthesis, unknown players remain to be identified, given that it is a complicated and sophisticated process. The endosperm of rice (Oryza sativa) has been used for the study of starch synthesis. Here, we report the cloning and characterization of the FLOURY ENDOSPERM6 (FLO6) gene in rice. In the flo6 mutant, the starch content is decreased and the normal physicochemical features of starch are changed. Significantly, flo6 mutant endosperm cells show obvious defects in compound granule formation. Map-based cloning showed that FLO6 encodes a protein of unknown function. It harbors an N-terminal transit peptide that ensures its correct localization and functions in the plastid, and a C-terminal carbohydrate-binding module 48 (CBM48) domain that binds to starch. Furthermore, FLO6 can interact with isoamylase1 (ISA1) both in vitro and in vivo, whereas ISA1 does not bind to starch directly. We thus propose that FLO6 may act as a starch-binding protein involved in starch synthesis and compound granule formation through a direct interaction with ISA1 in developing rice seeds. Our data provide a novel insight into the role of proteins with the CBM48 domain in plant species.
State Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing, 210095, China.
Cheng
C
Peng
Yihua
Y
Wang
Feng
F
Liu
Yulong
Y
Ren
Kunneng
K
Zhou
Jia
J
Lv
Ming
M
Zheng
Shaolu
S
Zhao
Long
L
Zhang
Chunming
C
Wang
Ling
L
Jiang
Xin
X
Zhang
Xiuping
X
Guo
Yiqun
Y
Bao
Jianmin
J
Wan
D001483:Base Sequence; D050260:Carbohydrate Metabolism; D002874:Chromosome Mapping; D056625:Endosperm / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D008969:Molecular Sequence Data; D009154:Mutation; D012275:Oryza / Q000166:cytology / Q000235:genetics* / Q000378:metabolism; D010641:Phenotype; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D017434:Protein Structure, Tertiary; D012639:Seeds / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D013213:Starch / Q000378:metabolism*
D010940:Plant Proteins; D013213:Starch
FLOURY ENDOSPERM6; Oryza sativa; carbohydrate-binding module 48; compound granule; rice; starch synthesis