Analysis of Ribulose-1,5-biphosphate Carboxylase/Oxygenase (Rubisco) Expression in the Fruit of Lycopersicum pimpinellifolium (Tomato) During the Ripening Process
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Abstract:
Rubisco, a multimeric complex, is comprised of 8 small subunits encoded within nuclear DNA, and 8 large protein subunits, encoded with chloroplast DNA. This study was designed to identify whether the expression of Rubisco differs in the tomato fruit of field grown Lycopersicum pimpinellifolium as they mature. During the maturation of the tomato fruit chloroplasts within the fruit differentiate into chromoplasts while maintaining the same genetic information. Therefore, a varied amount of Rubisco protein would indicate variation in gene expression. Total protein was isolated and purified from tomato fruit and leaves. The levels of the Rubisco gene and large Rubisco subunit (RBCL) protein were assessed. RBCL appeared to be present in similar levels in the green and orange fruit tissues and lower levels in the red tomato tissue. A comparison of the quantity of Rubisco gene to the quantity of protein expression within the 3 tissues indicated that although the number of copies of the Rubisco gene is greatest in the red tomato fruit, the level of Rubisco protein expression is the lowest. This would indicate that although chloroplasts differentiate into chromoplasts during the tomato ripening process additional chromoplasts must be synthesized to allow for enough of the red pigment to be produced. The knowledge gained from this analysis may be applied to the development of an efficient model for the indoor farming of tomatoes, allowing for the adjustment of artificial light levels, as the Rubsico levels, and the photosynthetic capacity of the plant decrease. This would allow for indoor farmers to efficiently use artificial lighting, and save money on yearly electric costs.
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