A TILLING allele of the tomato Aux/IAA9 gene offers new insights into fruit set mechanisms and perspectives for breeding seedless tomatoes
Author(s)
Date Issued
2015
Type
article
Volume
35
Issue
35
Start Page
22
End Page
36
ISSN
13803743
Journal
Abstract
Parthenocarpy is a desired trait in fruit
crops; it enables fruit set under environmental conditions
suboptimal for pollination, and seedless fruits
represent a valuable consumer product. We employed
TILLING-based screening of a mutant tomato population
to find genetic lesions in Aux/IAA9, a negative
regulator of the auxin response involved in the control
of fruit set. We identified three mutations located in
the coding region of this gene, including two singlebase
substitutions and one single-base deletion, which
leads to a frame shift and premature stop codon. The
transcription of IAA9 was strongly reduced in the
frame-shift mutant, and partial loss of mutated protein
activity was evidenced by an in vitro transactivation
assay. Whereas missense mutations were predicted to
be tolerated and did not cause mutant phenotypes, the
frame-shift mutation-induced phenotypes expected for
a loss of IAA9 function, including altered axillary
shoot growth, reduced leaf compoundness and a strong
tendency to produce parthenocarpic fruits. Mutant
flowers showed pleiotropic anther cone defects, a
phenotype frequently associated with parthenocarpy
in tomato and other species. Mutant fruits were larger
than those of the seeded control, with higher brix
values and similar firmness. Fruit set was higher in the
mutant than in wild type in the greenhouse, but lower
in the open field. Facultative expression of parthenocarpy
indicated that the mutant is suitable for hybrid
seed production and for increasing seeds of parental
lines. The results highlight the utility of this novel
IAA9 allele for exploiting parthenocarpy by breeding
tomato adapted to pollination-limiting growth
conditions.
Subjects
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Conference(s)
MOLECULAR BREEDING