title: Natural mutations in two homoeologous TT8 genes control yellow seed coat trait in allotetraploid Brassica juncea (AABB).
abstract: Identification of the candidate gene responsible for the seed coat colour variation in Brassica juncea was undertaken following an earlier study where two independent loci (BjSc1 and BjSc2) were mapped to two linkage groups, LG A9 and B3 (Padmaja et al. in Theor Appl Genet 111:8-14, 2005). The genome search from BRAD data for the presence of flavonoid genes in B. rapa identified three candidate genes namely, DFR, TT1 and TT8 in the LG A9. Quantitative real-time PCR revealed absence of transcript for the late biosynthetic genes (LBGs) and showed significant reduction of transcript in the TT8 from the developing seeds of yellow-seeded line. While mapping of two DFR genes, the BjuA.DFR and BjuB.DFR did not show perfect co-segregation with the seed coat colour loci, that of the two TT8 genes, BjuA.TT8 and BjuB.TT8 showed perfect co-segregation with the seed coat colour phenotype. The BjuA.TT8 allele from the yellow-seeded line revealed the presence of an insertion of 1,279 bp in the exon 7 and did not produce any transcript as revealed by reverse transcriptase PCR. The BjuB.TT8 allele from the yellow-seeded line revealed the presence of an SNP (C→T) in the exon 7 resulting in a stop codon predicting a truncated protein lacking the C-terminal 8 amino acid residues and produced significantly low level of transcript than its wild-type counterpart. Hence, it is hypothesized that the mutations in both the TT8 genes are required for inhibiting the transcription of LBGs in the yellow-seeded mutant of B. juncea.
authors.affiliation: Centre for Genetic Manipulation of Crop Plants, University of Delhi South Campus, Benito Juarez Road, New Delhi, 110021, India.
authors.forename: Lakshmi K
authors.initials: LK
authors.lastname: Padmaja
authors.forename: Parul
authors.initials: P
authors.lastname: Agarwal
authors.forename: Vibha
authors.initials: V
authors.lastname: Gupta
authors.forename: Arundhati
authors.initials: A
authors.lastname: Mukhopadhyay
authors.forename: Yaspal S
authors.initials: YS
authors.lastname: Sodhi
authors.forename: Deepak
authors.initials: D
authors.lastname: Pental
authors.forename: Akshay K
authors.initials: AK
authors.lastname: Pradhan
mesh_terms: D001937:Brassica / Q000196:embryology / Q000235:genetics*; D009154:Mutation; D010940:Plant Proteins / Q000235:genetics*; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012639:Seeds / Q000235:genetics*; D057891:Tetraploidy
chemical_list: D010940:Plant Proteins