title: Transposable element rbg induces the differential expression of opaque-2 mutant gene in two maize o2 NILs derived from the same inbred line.
abstract: The recessive opaque-2 mutant gene (o2) reduces α-zeins accumulation in maize endosperm, changes the amino acid composition of maize kernels, induces an opaque endosperm, and increases the lysine content of kernels. The quality protein maize (QPM) inbred line CA339 (o2o2) and an elite normal inbred line liao2345 (O2O2) were used to construct o2 near-isogenic lines (NILs) by marker-assisted selection (MAS) using the co-dominant SSR marker phi057. Two specific o2 NILs were constructed, named liao2345/o2-1 and liao2345/o2-2. However, the kernel phenotypes of the two o2 NILs were different from each other. liao2345/o2-1 had the wild-type vitreous endosperm, which is similar to its recurrent parent liao2345, while the endosperm of liao2345/o2-2 was opaque, identical to typical o2 mutant individuals. In comparison to their recurrent parent liao2345, the lysine concentration of liao2345/o2-1 was similar and the lysine concentration in liao2345/o2-2 was doubled. SDS-PAGE analysis indicated that liao2345/o2-1 had the same zeins ratio as liao2345, whereas the zeins concentration of liao2345/o2-2 was markedly lower. Sequence and transcript abundance analyses indicated that the CDS of two o2 NILs are derived from CA339, but they have different promoters. The O2 transcript of liao2345/o2-2 is largely inhibited because of an rbg transposable element inserted between the TATA box and initiator codon of liao2345/o2-2. We concluded that different crossing-over patterns during the process of o2 NIL construction resulted in the different kernel phenotypes of the two o2 NILs. We surmise that the reversion of liao2345/o2-1 to wild type was due to the recombination with the wild type liao2345 promoter during introgression and backcrossing. The o2 mutant gene of donor (CA339) is a null mutant because of low O2 expression. However, its CDS probably encodes a protein with normal function which can maintain the normal accumulation of zeins in maize endosperm.
authors.affiliation: Department of Crop Genetics and Breeding, Institute of Crop Sciences, Chinese Academy of Agricultural Science, Beijing, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Crop Genetics and Breeding, Institute of Crop Sciences, Chinese Academy of Agricultural Science, Beijing, China.
authors.forename: Zhiqiang
authors.initials: Z
authors.lastname: Zhou
authors.affiliation: Department of Crop Genetics and Breeding, Institute of Crop Sciences, Chinese Academy of Agricultural Science, Beijing, China.
authors.forename: Gang
authors.initials: G
authors.lastname: Zhao
authors.affiliation: Department of Crop Genetics and Breeding, Institute of Crop Sciences, Chinese Academy of Agricultural Science, Beijing, China.
authors.forename: Xinhai
authors.initials: X
authors.lastname: Li
authors.affiliation: Beijing Key Lab of Plant Resource Research and Development, Beijing Technology and Business University, Beijing, China.
authors.forename: Liya
authors.initials: L
authors.lastname: Song
authors.affiliation: Department of Crop Genetics and Breeding, Institute of Crop Sciences, Chinese Academy of Agricultural Science, Beijing, China.
authors.forename: Na
authors.initials: N
authors.lastname: Yan
authors.affiliation: Department of Crop Genetics and Breeding, Institute of Crop Sciences, Chinese Academy of Agricultural Science, Beijing, China.
authors.forename: Jianfeng
authors.initials: J
authors.lastname: Weng
authors.affiliation: Department of Crop Genetics and Breeding, Institute of Crop Sciences, Chinese Academy of Agricultural Science, Beijing, China.
authors.forename: Zhuanfang
authors.initials: Z
authors.lastname: Hao
authors.affiliation: Department of Crop Genetics and Breeding, Institute of Crop Sciences, Chinese Academy of Agricultural Science, Beijing, China.
authors.forename: Degui
authors.initials: D
authors.lastname: Zhang
authors.affiliation: Department of Crop Genetics and Breeding, Institute of Crop Sciences, Chinese Academy of Agricultural Science, Beijing, China.
authors.forename: Mingshun
authors.initials: M
authors.lastname: Li
authors.affiliation: Department of Crop Genetics and Breeding, Institute of Crop Sciences, Chinese Academy of Agricultural Science, Beijing, China.
authors.forename: Shihuang
authors.initials: S
authors.lastname: Zhang
mesh_terms: D001947:Breeding; D003062:Codon; D003433:Crosses, Genetic; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D056625:Endosperm / Q000235:genetics* / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D005819:Genetic Markers; D005838:Genotype; D008239:Lysine / Q000378:metabolism; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics* / Q000378:metabolism; D011995:Recombination, Genetic; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D003313:Zea mays / Q000235:genetics* / Q000378:metabolism; D015028:Zein / Q000235:genetics / Q000378:metabolism
chemical_list: D003062:Codon; D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins; D005819:Genetic Markers; D010940:Plant Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; C067402:opaque-2 protein, Zea mays; D015028:Zein; D008239:Lysine