Environmental Conditions Influencing the Development of Tomato Pockets or Puffs

Foster, Arthur C.; Tatman, Everett C.

doi:10.1126/science.86.2218.21

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“…Our analysis showed that many commercially available tomato cultivars and also experimentally used lines that have been selfed for many generations show some degree of natural parthenocarpy following emasculation ranging from ovary expansion to varying sized seedless fruits. Some of these small and misshapen fruits are likely to be similar to those referred to as pseudofruits, puffs, or nuts in the literature (Foster and Tatman, 1937;Vardy et al, 1989a;Pandolfini et al, 2002;Carmi et al, 2003). We have previously demonstrated that parthenocarpy in Arabidopsis arf8 mutants is not expressed if floral whorls surrounding the carpel are not removed, as signals from these tissues inhibit the expression of parthenocarpy .…”

Section: Genetics Expression and Induction Of Parthenocarpy In Tomatomentioning

confidence: 80%

Expression of Aberrant Forms ofAUXIN RESPONSE FACTOR8Stimulates Parthenocarpy in Arabidopsis and Tomato

et al. 2007

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Fruit initiation in Arabidopsis (Arabidopsis thaliana) is generally repressed until fertilization occurs. However, mutations in AUXIN RESPONSE FACTOR8 (ARF8) uncouple fruit initiation from fertilization, resulting in the formation of seedless, parthenocarpic fruit. Here we induced parthenocarpy in wild-type Arabidopsis by introducing either the mutant genomic (g) Atarf8-4 sequence or gAtARF8:b-glucuronidase translational fusion constructs by plant transformation. Silencing of endogenous AtARF8 transcription was not observed, indicating that the introduced, aberrant ARF8 transcripts were compromising the function of endogenous ARF8 and/or associated factors involved in suppressing fruit initiation. To analyze the role of ARF8 in tomato (Solanum lycopersicum) we initially emasculated 23 tomato cultivars to test for background parthenocarpy. Surprisingly, all had a predisposition to initiate fertilization-independent fruit growth. Expression of gAtarf8-4 in transgenic tomato ('Monalbo') resulted in a significant increase in the number and size of parthenocarpic fruit. Isolation of tomato ARF8 cDNA indicated significant sequence conservation with AtARF8. SlARF8 may therefore control tomato fruit initiation in a similar manner as AtARF8 does in Arabidopsis. Two SlARF8 cDNAs differing in size by 5 bp were found, both arising from the same gene. The smaller cDNA is a splice variant and is also present in Arabidopsis. We propose that low endogenous levels of the splice variant products might interfere with efficient formation/function of a complex repressing fruit initiation, thereby providing an explanation for the observed ovary expansion in tomato and also Arabidopsis after emasculation. Increasing the levels of aberrant Atarf8-4 transcripts may further destabilize formation/function of the complex in a dosage-dependent manner enhancing tomato parthenocarpic fruit initiation frequency and size and mimicking the parthenocarpic dehiscent silique phenotype found in homozygous Atarf8-4 mutants. Collectively these data suggest that similar mechanisms involving auxin signaling exist to inhibit parthenocarpic fruit set in tomato and Arabidopsis.

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Section: Genetics Expression and Induction Of Parthenocarpy In Tomatomentioning

confidence: 80%