Abstract:
The classical ethyl methanesulfonate (EMS) tomato mutant bushy root (brt) was
studied using a homozygous near isogenic line (brtNIL) in the Micro-Tom (MT)
genetic background. The mutation has a pleiotropic phenotype comprising slow
seedling development, which may be a consequence of a maternally-inherited
small seed phenotype, and a more compact, smaller but not bushier, root
phenotype. The number of lateral roots, total root length and taproot size are all
smaller in brtNIL than the WT. The BRT locus was mapped to a 137 kbp region
containing 9 candidate genes on chr 12; an InDel in the promoter region of
Solyc12g014590 – containing two highly conserved pirin domains (Pirin_C and
Pirin), was detected. Different expression patterns were confirmed by
transcriptomic results, supporting Solyc12g014590 as the gene responsible for
the brt phenotype.
A naturally occurring recessive mutant named bifuricate (bif) shows an
increase in inflorescence (truss) branching in comparison to the wild type (WT)
control line, LAM183. In addition, the number of flowers per truss was 235%
higher in bif plants than WT. Low temperature is known to increase truss
branching, and so a four day low temperature treatment was applied and it was
demonstrated that flowering increased significantly more in bif than in LAM183.
The BIF locus was mapped to a 2.01 Mbp interval of chromosome 12 containing
53 genes. All coding region polymorphisms in the interval were surveyed, and
two genes Solyc12g019420 (a BTB/TAZ transcription factor) and
Solyc12g019460 (a MAP kinase) contained one stop codon predicted to disrupt
gene function; both genes are excellent candidates for inflorescence branching
control based on literature evidence. A newly developed introgression browser
was used to demonstrate that the origin of the bif mutant haplotype is Solanum
galapagense.
