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J Exp Bot. 2016 Feb;67(3):633-47. doi: 10.1093/jxb/erv469. Epub 2015 Nov 24.

FLOURY ENDOSPERM7 encodes a regulator of starch synthesis and amyloplast development essential for peripheral endosperm development in rice.

Author information

1
State Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing 210095, PR China.
2
National Key Facility for Crop Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing 100081, PR China.
3
College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, PR China.
4
State Key Laboratory for Crop Genetics and Germplasm Enhancement, Jiangsu Plant Gene Engineering Research Center, Nanjing Agricultural University, Nanjing 210095, PR China National Key Facility for Crop Resources and Genetic Improvement, Institute of Crop Science, Chinese Academy of Agricultural Sciences, Beijing 100081, PR China wanjianmin@caas.cn wanjm@njau.edu.cn.

Abstract

In cereal crops, starch synthesis and storage depend mainly on a specialized class of plastids, termed amyloplasts. Despite the importance of starch, the molecular machinery regulating starch synthesis and amyloplast development remains largely unknown. Here, we report the characterization of the rice (Oryza sativa) floury endosperm7 (flo7) mutant, which develops a floury-white endosperm only in the periphery and not in the inner portion. Consistent with the phenotypic alternation in flo7 endosperm, the flo7 mutant had reduced amylose content and seriously disrupted amylopectin structure only in the peripheral endosperm. Notably, flo7 peripheral endosperm cells showed obvious defects in compound starch grain development. Map-based cloning of FLO7 revealed that it encodes a protein of unknown function. FLO7 harbors an N-terminal transit peptide capable of targeting functional FLO7 fused to green fluorescent protein to amyloplast stroma in developing endosperm cells, and a domain of unknown function 1338 (DUF1338) that is highly conserved in green plants. Furthermore, our combined β-glucuronidase activity and RNA in situ hybridization assays showed that the FLO7 gene was expressed ubiquitously but exhibited a specific expression in the endosperm periphery. Moreover, a set of in vivo experiments demonstrated that the missing 32 aa in the flo7 mutant protein are essential for the stable accumulation of FLO7 in the endosperm. Together, our findings identify FLO7 as a unique plant regulator required for starch synthesis and amyloplast development within the peripheral endosperm and provide new insights into the spatial regulation of endosperm development in rice.

KEYWORDS:

Amyloplast; DUF1338; FLOURY ENDOSPERM7; endosperm cells; rice (Oryza sativa); starch synthesis.

PMID:
26608643
PMCID:
PMC4737065
DOI:
10.1093/jxb/erv469
[Indexed for MEDLINE]
Free PMC Article

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