Growth modulation of transgenic potato plants by heterologous expression of bacterial carbohydrate-binding module

Transgenic potato plants (Solanum tuberosum cv. Desiree) expressing the bacterial carbohydrate-binding module (CBM) family III, which is part of the Clostridium cellulovorans CBPA, under control of the CaMV 35S promoter were employed to investigate the influence of this protein on plant development. Eleven independent transgenic plants were found to express the cbm gene, at levels varying from one to four copies. Relative to non-transgenic controls, CBM-expressing plants were characterized by significantly more rapid elongation of the main stem. In addition, under both greenhouse and field conditions, the emergence rate of these plants was higher than in the controls, and their leaf area at early stages of development was larger, resulting in faster accumulation of fresh and dry weight than in control plants. Determination of cell size indicated that epidermal cells in young tissue were significantly larger in CBM-expressing than in control potato plants. These findings suggest that the CBM influence at the cellular level my cause significant alterations in plant growth both in tissue culture and in vivo under field conditions.