Figure 3

PCR screening of a mutant pool bank identifies an insertion in the CBP1 locus. Twenty-four pools of T-DNA insertion mutants were screened by primary PCR (A) and nested PCR (B) with primer sets specific for the CBP1 gene. (A) Template nucleic acids from 24 mutant pools (each comprised of 100-200 individual mutants) were screened with the RB3 and CBP1-21 primers. The reaction products for each pool were separated in individual lanes by electrophoresis through 1% agarose. (B) Primary PCR reactions from (A) were diluted 1:10,000 and used as template for nested PCR with RB6 and CBP1-23 primers. The potential cbp1::T-DNA mutant was found only in pool #12. (C) Schematic depiction of the identified cbp1::T-DNA insertion. The T-DNA insertion from pool #12 was designated OSU8. Sequencing of the PCR product from regions flanking the insertion localized the T-DNA element insertion site 234 base pairs (bp) upstream of the CBP1 coding region. Nucleotide sequences flanking the T-DNA insertion in the mutant (top row) aligned with the T-DNA left border (LB) and right border (RB) imperfect direct repeats (bottom row) show the nature of the mutational event. Numbers above the mutant sequence correspond to nucleotides of the wild-type CBP1 promoter.