Induction of male sterility in plants by metabolic engineering of the carbohydrate supply

Extracellular invertase mediates phloem unloading via an apoplastic pathway . The gene encoding isoenzyme Nin88 from tobacco was cloned and shown to be characterized by a specific spatial and temporal expression pattern. Tissu e-specific antisense repression of Nin88 under control of the corresponding promoter in tobacco results in a block during early stages of pollen devel opment, thus, causing male sterility. This result demonstrates a critical r ole of extracellular invertase in pollen development and strongly supports the essential function of extracellular sucrose cleavage for supplying carb ohydrates to sink tissues via the apoplast, The specific interference with phloem unloading, the sugar status, and metabolic signaling during pollen f ormation will be a potentially valuable approach to induce male sterility i n various crop species for hybrid seed production.