Mutations of the multi-drug resistance-associated protein ABC transporter gene 5 result in reduction of phytic acid in rice seeds.
Phytic acid (PA, myo-inositol 1,2,3,4,5,6-hexakisphosphate) is important to the nutritional quality of cereal and legume seeds. PA and its salts with micronutrient cations, such as iron and zinc, cannot be digested by humans and non-ruminant animals, and hence may affect food/feed nutritional value and cause P pollution of groundwater from animal waste. We previously developed a set of low phytic acid (LPA) rice mutant lines with the aim of increasing the nutritional quality of rice. Two of these lines, Os-lpa-XS110-2 (homozygous non-lethal) Os-lpa-XS110-3 (homozygous lethal), contain two mutant alleles of a LPA gene (hereafter XS-lpa2-1 and XS-lpa2-2, respectively). In this study, we mapped the XS-lpa2-1 gene to a region on chromosome 3 between microsatellite markers RM14360 and RM1332, where the rice orthologue (OsMRP5) of the maize lpa1 gene is located. Sequence analysis of the OsMRP5 gene revealed a single base pair change (C/G-T/A transition) in the sixth exon of XS-lpa2-1 and a 5-bp deletion in the first exon of XS-lpa2-2. OsMRP5 is expressed in both vegetative tissues and developing seeds, and the two mutations do not change the level of RNA transcription. A T-DNA insertion line, 4A-02500, in which OsMRP5 was disrupted, also showed the same high inorganic phosphorus phenotype as Os-lpa-XS110-3 and appeared to be homozygous lethal. PA is significantly reduced in Os-lpa-XS110-2 (~20%) and in 4A-02500 (~90%) seeds compared with their wild type lines, and no PA was detected in Os-lpa-XS110-3 using HPLC analysis. This evidence indicates that the OsMRP5 gene plays an important role in PA metabolism in rice seeds.
Xu
Xiu-Hong
XH
IAEA-Zhejiang University Collaborating Center, and National Key Laboratory of Rice Biology, Institute of Nuclear Agricultural Sciences, Zhejiang University, Hangzhou, China.
Zhao
Hai-Jun
HJ
Liu
Qing-Long
QL
Frank
Thomas
T
Engel
Karl-Heinz
KH
An
Gynheung
G
Shu
Qing-Yao
QY
D000818:Animals; D002874:Chromosome Mapping; D004269:DNA, Bacterial / Q000235:genetics; D018432:Drug Resistance, Multiple / Q000235:genetics*; D018506:Gene Expression Regulation, Plant; D055786:Gene Knockout Techniques; D017343:Genes, Plant; D006801:Humans; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics*; D009154:Mutation; D012275:Oryza / Q000033:anatomy & histology / Q000235:genetics* / Q000378:metabolism; D010641:Phenotype; D010833:Phytic Acid / Q000378:metabolism*; D010940:Plant Proteins / Q000235:genetics*; D012639:Seeds / Q000737:chemistry* / Q000378:metabolism
D004269:DNA, Bacterial; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D010833:Phytic Acid; D010940:Plant Proteins; C036483:T-DNA