Heterologous expression of arabidopsis phytochrome B in transgenic potato influences photosynthetic performance and tuber development

Transgenic potato (Solanum toberosum) plants expressing Arabidopsis phytoch rome B were characterized morphologically and physiologically under white l ight in a greenhouse to explore their potential for improved photosynthesis and higher tuber yields. As expected, overexpression of functional phytoch rome B caused pleiotropic effects such as semidwarfism, decreased apical do minance, a higher number of smaller but thicker leaves, and increased pigme ntation. Because of increased numbers of chloroplasts in elongated palisade cells, photosynthesis per leaf area and in each individual plant increased . In addition, photosynthesis was less sensitive to photoinactivation under prolonged light stress. The beginning of senescence was not delayed, but d eceleration of chlorophyll degradation extended the lifetime of photosynthe tically active plants. Both the higher photosynthetic performance and the l onger lifespan of the transgenic plants allowed greater biomass production, resulting in extended underground organs with increased tuber yields.