Trihalogenated methylsulfonamides as specific male gametocides

A new class of male gametocide is described: trihalomethylsulfonamides, the most active example of this class being trifluoromethylsulfonamide (TFMSA). TFMSA induces male sterility, specifically, without detectable effects on other plant functions. Male sterility induction in maize (Zea mays, gaspe flint) required minimally 200 g TFMSA per plant and this rate was used in a metabolite sampling time-course experiment to determine the earliest detectable change in metabolites of developing florets. Metabolites profiled were amino acids, callose, fatty acids, flavones, phenylpropenoids, sporopollenin and starch, all of which are related to successful pollen development. Changes in proline and starch were the earliest statistically significant differences observed between florets of control plants and TFMSA-treated plants. These metabolic differences were observed before symptoms of pollen failure were evident. In subsequent experiments, transient increases in glume proline and decreases in anther proline were linearly related to sub-effective rates of TFMSA (0, 25, 50, 75 and 100 g plant^–1). Increases in glume proline faded during development whereas decreases in anther proline linearly related to TFMSA rate became more prominent. Changes in all other metabolites profiled were not linearly related to TFMSA rate. Related experiments showed that florets from TFMSA-treated plants were not capable of converting ¹⁴C-glutamate to ¹⁴C-proline, and the anther transport capacity of ¹⁴C-proline in TFMSA-treated plants was significantly reduced. It is inferred that TFMSA induces male sterility by interfering with the transport of proline from the site of synthesis to the site of accumulation, resulting in feedback inhibition of proline biosynthesis, ultimately starving the developing anther of proline.