Lose-of-Function of a Rice Nucleolus-Localized Pentatricopeptide Repeat Protein Is Responsible for the floury endosperm14 Mutant Phenotypes

Mengyao Xue,Linglong Liu,Jianmin Wan,Yihua Wang,Hao Gao,Jianping Zhu,Yanfang Yu

doi:10.1186/s12284-019-0359-x

Mengyao Xue, Linglong Liu + Show 5 more

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https://doi.org/10.1186/s12284-019-0359-x

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Abstract

BackgroundThe endosperm of rice (Oryza sativa) has been usually used for the study of starch synthesis. Although several related factors have been revealed, other unknown members remain to be identified, given that starch synthesis is a complicated and sophisticated process.ResultsHere, we identified and characterized a new rice seed mutant, floury endosperm14 (flo14), which showed chalked endosperm and seed-lethal phenotypes. Map-based cloning indicated FLO14 encodes a novel P-family PPR protein which contains ten PPR motifs. Afterwards the gene was named OsNPPR3. Subcellular localization showed OsNPPR3 was targeted to nucleolus. Quantitative RT-PCR analysis demonstrated that OsNPPR3 was universally expressed in various tissues, with pronounced levels during rice endosperm development. Molecular analysis further suggested that OsNPPR3 was involved in the regulation of expression levels and splicing of a few genes in mitochondria.ConclusionThe study demonstrates that the nucleolus-localized PPR protein is responsible for the flo14 mutant phenotypes through affecting nuclear and mitochondrial gene expression and splicing.

Highlights

The endosperm of rice (Oryza sativa) has been usually used for the study of starch synthesis
The flo14 mutant was backcrossed twice with background parent to exclude the possibility of other gene variants, and the mutant seeds could only be collected from heterozygous individuals
Vertical-sections of imbibed seeds showed that wild-type embryos were well developed with established coleoptiles and shoot apical meristems, whereas only incomplete coleoptile structures were observed in the flo14 embryos (Fig. 1c)

Summary

Introduction

The endosperm of rice (Oryza sativa) has been usually used for the study of starch synthesis. Some related factors involved in starch biosynthesis have been reported in rice (Long et al, 2017), there still existed a large number of unknown genes related to starch synthesis in rice. Floury endosperm (flo) mutants are ideal genetic materials for studying the mechanism of starch biosynthesis and amyloplast development. The first floury endosperm mutant (flo1) was previously reported to locate on chromosome 5, and the causative gene was not yet identified (Satoh and Omura, 1981). Further study showed the OsPPDKB/FLO4 gene could act as an important modulator of carbon flow for starch and lipid biosynthesis during grain filling (Kang et al, 2005). The OsSSSIIIa/FLO5 protein played an important role in generating relatively long chains in rice endosperm (Ryoo et al, 2007).

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