Abstract
Tomato is one of the most widely cultivated vegetable crops and a model for studying fruit biology. Although several genes involved in the traits of fruit quality, development and size have been identified, little is known about the regulatory genes controlling its growth. In this study, we characterized the role of the tomato SlCDF4 gene in fruit development, a cycling DOF-type transcription factor highly expressed in fruits. The targeted overexpression of SlCDF4 gene in the fruit induced an increased yield based on a higher amount of both water and dry matter accumulated in the fruits. Accordingly, transcript levels of genes involved in water transport and cell division and expansion during the fruit enlargement phase also increased. Furthermore, the larger amount of biomass partitioned to the fruit relied on the greater sink strength of the fruits induced by the increased activity of sucrose-metabolising enzymes. Additionally, our results suggest a positive role of SlCDF4 in the gibberellin-signalling pathway through the modulation of GA4 biosynthesis. Finally, the overexpression of SlCDF4 also promoted changes in the profile of carbon and nitrogen compounds related to fruit quality. Overall, our results unveil SlCDF4 as a new key factor controlling tomato size and composition.
Highlights
Tomato is one of the most widely cultivated vegetable crops and a model for studying fruit biology
To explore the function of the gene in greater detail, we studied the expression of the Solanum lycopersicum CDF4 gene (SlCDF4) gene during fruit development and qRT-PCR analysis was performed in non-transformed Moneymaker (MM) fruits at 5, 10, 15, 20, 30 and 40 DAA (Fig. 1)
To further understand the relationship of SlCDF4 with the auxin and gibberellin signalling pathways, we investigated the expression of the AUXIN RESPONSE FACTOR 5 (SlARF5) gene, involved in the determination of tomato fruit size, and the Aux/indole-acetic acid (IAA) transcription factor SlIAA17, reported to participate in auxin signalling during the fruit cell e xpansion[16,23]
Summary
Tomato is one of the most widely cultivated vegetable crops and a model for studying fruit biology. We characterized the role of the tomato SlCDF4 gene in fruit development, a cycling DOF-type transcription factor highly expressed in fruits. The targeted overexpression of SlCDF4 gene in the fruit induced an increased yield based on a higher amount of both water and dry matter accumulated in the fruits. Transcript levels of genes involved in water transport and cell division and expansion during the fruit enlargement phase increased. Cell division is the main process by which fruits increase in size in the early stages. Besides the fruit-level processes involved in the determination of the final size, total yield is influenced by environmental factors, fruit load and, by photoassimilate availability at whole plant level[7]. The availability of carbon compounds depends on the photosynthetic activity of the source leaves and the partition and allocation. Sucrose-metabolism enzymes, such as invertase, in the fruits maintain the gradient of transport from sources to sinks, and the import into the fruit[11,12]
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