20 research outputs found
Tomato fruit set driven by pollination or by the parthenocarpic fruit allele are mediated by transcriptionally regulated gibberellin biosynthesis
We investigated the role of gibberellins (GAs) in
the phenotype of parthenocarpic fruit (pat), a recessive
mutation conferring parthenocarpy in tomato (Solanum lycopersicum
L.). Novel phenotypes that parallel those reported
in plants repeatedly treated with gibberellic acid or having a
GA-constitutive response indicate that the pat mutant probably
expresses high levels of GA. The retained sensitivity to
the GA-biosynthesis inhibitor paclobutrazol reveals that this
condition is dependent on GA biosynthesis. Expression analysis
of genes encoding key enzymes involved in GA biosynthesis
shows that in normal tomato ovaries, the GA20ox1
transcript is in low copy number before anthesis and only
pollination and fertilization increase its transcription levels
and, thus, GA biosynthesis. In the unpollinated ovaries of
the pat mutant, this mechanism is de-regulated and
GA20ox1 is constitutively expressed, indicating that a high
GA concentration could play a part in the parthenocarpic
phenotype. The levels of endogenous GAs measured in the
Xoral organs of the pat mutant support such a hypothesis.
Collectively, the data indicate that transcriptional regulation
of GA20ox1 mediates pollination-induced fruit set in tomato
and that parthenocarpy in pat results from the mis-regulation
of this mechanism. As genes involved in the control of GA
synthesis (LeT6, LeT12 and LeCUC2) and response (SPY)
are also altered in the pat ovary, it is suggested that the pat
mutation aVects a regulatory gene located upstream of the
control of fruit set exerted by GAs