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Crop Biotech Update

Hybrid Rubisco of Tomato Large Subunits and Tobacco Small Subunits are Functional in Tobacco Plants

February 18, 2011

During photosynthesis, plants convert carbon dioxide into sugar precursor through the activity of an enzyme called ribulose-1,5-biphosphate carboxylase/oxygenase (Rubisco). Rubisco has been known as the most important enzyme not just in photosynthesis but also in biomass productivity and carbon dioxide sequestration. However, Rubisco has very low catalytic efficiency, using only 20 to 70 carbon dioxide molecules per second. This led scientists to improve the activity of the enzyme Rubisco, but most studies on improving its functionality have been unsuccessful.

 Xing-Hai Zhang from Florida Atlantic University, together with other scientists, created two lines of tobacco plants with rbcL gene coming from tomato with the objective of improving the activity of Rubisco. The first line, labeled as plant LLS2, contains Rubisco with the small subunit from tobacco and Q437R large subunit. The second line is called plant LLS4, with a hybrid Rubisco from tobacco small subunit, and tomato large subunit.

According to the results, plant LLS2 has similar phenotype with the wild type; while plant LLS4 exhibited decreased chlorophyll and Rubisco levels, lower photosynthesis rates and biomass, especially during the early development stages. However, plant LLS4 was able to achieve reproductive maturity with similar characteristics with the wild type. Both plant lines also exhibited comparable carboxylase activity and RuBP affinity as in the wild type. The hybrid Rubisco of tomato large subunit and tobacco small subunit can efficiently drive photosynthesis to support growth and reproduction of tobacco plants.

Read more about the results and discussions at