Time Course of the Expression of the CaMV35S-GUS Gene in Transgenic Lettuce Plants Grown in a Plant Factory

Leaf lettuce (Lactuca sativa L. cv. “Greenwave”) containing an introduced Cauliflower mosaic virus-35S promoter fused onto the the β-glucuronidase (GUS) gene was grown in a plant factory for 50 days from seeding. Measurements of the GUS expression level of leaves indicated that the GUS protein that accumulated in the leaves was very stable and did not degrade. Consequently, the GUS expression per plant increased exponentially as the cultivation period became longer. This stability of the recombinant protein indicates that a longer cultivation period would be more efficient than the conventional cultivation period in a plant factory. However, the optimum cultivation period depends on the stability of the recombinant protein which is required.