Cloning and Expression of Gene Responsible for High-Tillering Dwarf Phenotype in Indica Rice Mutant gsor23

High-tillering dwarf mutant gsor23 was generated from an indica rice variety Indica9 radiatied by y-ray. Genetic analysis showed that this phenotype was controlled by one single recessive gene, which was mapped within a physical distance of 386 kb between two insertion-deletion （InDel） markers CI-WT2 and C1-WT4 on the long arm of chromosome 1. There is a known gene DIO within this region, the mutation of which causes high-tillering in rice. Sequence analysis of the DIO allele in gsor23 revealed that the base cytosine （C） at the 404th position in the coding region was deleted, which would cause frameshift mutation after the 134th amino acids. The mutation site and indica background of gsor23 were different from the previously reported japonica mutants d10-1 and d10-2. Therefore, gsor23 is a novel allelic mutant of D10 which encodes the carotenoid-cleaving dioxygenase 8 （CCD8）, a key enzyme involved in the biosynthesis of the new plant hormone strigolactones （SLs）. After treatment with GR24, a synthetic analogue of SLs, the high-tillering phenotype of gsor23 was restored to normal. Real-time RT-PCR analysis showed that D10 expression was high in roots, but low in leaves. Compared with the wild type Indica9, the expression of the SL biosynthesis gene DIO was upregulated, while genes likely involved in the SL signal transduction pathway such as D3 and D14 were down-regulated in the gsor23 mutant.

Differential SW16.1 allelic effects and genetic backgrounds contributed to increased seed weight after soybean domestication

Although seed weight has increased following domestication from wild soybean(Glycine soja) to cultivated soybean(Glycine max), the genetic basis underlying this change is unclear. Using mapping populations derived from chromosome segment substitution lines of wild soybean, we identified SW16.1 as the causative gene underlying a major quantitative trait locus controlling seed weight.SW16.1 encodes a nucleus-localized LIM domaincontaining protein. Importantly, the GsSW16.1 allele from wild soybean accession N24852 had a negative effect on seed weight, whereas the GmSW16.1 allele from cultivar NN1138-2 had a positive effect. Gene expression network analysis,reverse-transcription quantitative polymerase chain reaction, and promoter-luciferase reporter transient expression assays suggested that SW16.1 regulates the transcription of MT4, a positive regulator of seed weight. The natural variations in SW16.1 and other known seed weight genes were analyzed in soybean germplasm. The SW16.1 polymorphism was associated with seed weight in 247 soybean accessions, showing much higher frequency of positive-effect alleles in cultivated soybean than in wild soybean. Interestingly,gene allele matrix analysis of the known seed weight genes revealed that G. max has lost 38.5%of the G. soja alleles and that most of the lost alleles had negative effects on seed weight. Our results suggest that eliminating negative alleles from G. soja led to a higher frequency of positive alleles and changed genetic backgrounds in G. max,which contributed to larger seeds in cultivated soybean after domestication from wild soybean.Our findings provide new insights regarding soybean domestication and should assist current soybean breeding programs.

Identification of mutation in a candidate gene for hereditary multiple exostoses type Ⅱ

Objectives To identify possible mutations in our previously cloned candidate gene for hereditary multiple exostoses type Ⅱ (EXT2) in affected members of EXT families so as to confirm that it is the disease causing gene. Methods The mutation was detected first by single strand conformational polymorphism(SSCP) of all coding exons of the candidate gene and then by sequencing analysis. Results After analyzing 37 patients from 20 Chinese EXT families by SSCP and DNA sequencing analysis, one 2 bp insertion mutation was identified in this candidate gene in affected members of an EXT family. This mutation resulted in the frameshift and generated a truncated gene product consisting of 105 amino acids. Conclusions The identification of the mutation in the candidate gene indicates that this novel gene is responsible for EXT2 (one of the disease causing gene of EXT).