Partial male sterility induced in tobacco by overproduction of mRNA of sweet potato small subunit ADP-glucose pyrophosphorylase

Previously we generated transgenic tobacco plants overexpressing sweet potato ADP-glucose pyrophosphorylase (AGPase) small subunit cDNA under control of CaMV 35S promoter. In order to understand the role of small subunit AGPase in pollen development, these transgenic tobacco plants were studied. Nine out of ten transgenic tobacco plants produced more than 50% aborted pollen grains. The two transgenic lines T4 and T27 produced more than 75 % aborted pollen grains. Analysis of inheritance of the transgene inserts in T4 and T27 revealed that transgene co-segregated with the pollen abortion phenotype. Microscopic examination of aborted pollen grains showed that their cytoplasm did not contain starch granules, nuclei or any other organelles. Transcript levels of the transgene were very high in stamen tissues of transgenic plants. Transcript levels were correlated with the severity of the pollen abortion phenotype in transgenic plants, indicating that the pollen abortion phenotype probably resulted from overproduction of sweet potato small subunit AGPase mRNAs. Western blot analysis revealed that AGPase small subunit polypeptide levels were significantly reduced in stamen tissues of T4 and T27 compared with control plant. These results suggest that AGPase small subunit gene may play an important role in pollen development.