Two sequence alterations, a 136 bp InDel and an A/C polymorphic site, in the S5 locus are associated with spikelet fertility of indica-japonica hybrid in rice.
The rice indica/japonica hybrid shows strong heterosis. However, such inter-subspecific hybrid can't be directly used in rice production due to its low spikelet fertility. The S5 locus was proved to be associated with fertility of indica/japonica hybrid and its S5n allele from wide-compatibility variety (WCV) is capable to overcome fertility barrier. In the present study, we reported the causal sites in the S5 locus responsible for compatibility of indica/japonica hybrid. Fine-mapping of the S5 locus using the 11 test-cross families pinpoints a candidate S5 locus encoding aspartic protease (Asp). Intragenic recombination within the Asp gene happened in a number of recombinants, resulting in chimeric S5j-S5n alleles. Just like S5n, the chimeric S5j-S5n allele displayed higher spikelet fertility when combined with the S5i allele. In the complementary test, however, the S5n allele from WCVs failed to enhance fertilities of the indica/japonica hybrids. Compared to both indica and japonica varieties, all nine WCVs from different resources are characterized with a 136 bp deletion in the Asp N-terminus, which probably renders the S5n allele non-functional. Furthermore, an A/C polymorphic site is detected 1,233 bp downstream of the Asp start codon. The heterozygous A/C site of the Asp gene in indica/japonica hybrid is believed to be the casual factor to cause partial sterility. The functional makers based on the two polymorphic sites will be broadly used in developing wide-compatibility rice varieties.
Ji
Qing
Q
National Maize Improvement Center, China Agricultural University, Beijing 100193, China.
Lu
Jufei
J
Chao
Qing
Q
Zhang
Yan
Y
Zhang
Meijing
M
Gu
Minghong
M
Xu
Mingliang
M
D020029:Base Pairing / Q000235:genetics*; D001483:Base Sequence; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D005298:Fertility / Q000235:genetics; D017343:Genes, Plant / Q000235:genetics; D005816:Genetic Complementation Test; D056426:Genetic Loci / Q000235:genetics*; D005819:Genetic Markers / Q000235:genetics; D006824:Hybridization, Genetic; D054643:INDEL Mutation / Q000235:genetics*; D012275:Oryza / Q000145:classification / Q000235:genetics* / Q000502:physiology*; D011110:Polymorphism, Genetic; D011995:Recombination, Genetic; D015203:Reproducibility of Results
D005819:Genetic Markers