INHIBITION OF FLOWER FORMATION BY ANTISENSE REPRESSION OF MITOCHONDRIAL CITRATE SYNTHASE IN TRANSGENIC POTATO PLANTS LEADS TO A SPECIFIC DISINTEGRATION OF THE OVARY TISSUES OF FLOWERS

The tricarboxylic acid (TCA) cycle constitutes a major component of th e mitochondrial metabolism of eucaryotes, including higher plants, To analyze the importance of this pathway, we down-regulated mitochondria l citrate synthase (mCS; EC 4.1.3.7), the first enzyme of the TCA cycl e, in transgenic potato plants using an antisense RNA approach. Severa l transformants were identified with reduced citrate synthase activity (down to similar to 6% of wild-type activity). These plants were indi stinguishable from wild-type plants in the greenhouse during vegetativ e growth, A major change, however, was seen upon initiation of the gen erative phase (flower formation). In the case of transgenic plants wit h a strong reduction in citrate synthase activity (<30% of wild-type l evels), flower buds formed >2 weeks later as compared with wild-type p lants, Furthermore, flower buds from these plants did not develop into mature flowers but rather were aborted at an early stage of developme nt. Microscopic analysis showed that in these cases ovaries disintegra ted during flower development, We conclude that the TCA cycle is of ma jor importance during the transition from the vegetative to the genera tive phase.