Downregulation of OsAGO17 by artificial microRNA causes pollen abortion resulting in the reduction of grain yield in rice

Background: Pollen development is an important reproductive process that directly affects pollen fertility and grain yield in rice. Argonaute (AGO) proteins, the core effectors of RNA-mediated silencing, play important roles in regulating plant growth and development. However, few AGO proteins in rice were reported to be involved in pollen development. In this study, artificial microRNA technology was used to assess the function of OsAGO17 in pollen development. Results: In this study, OsAGO17, a rice-specific gene, was specifically expressed in rice pollen grains, with the highest expression in uninucleate microspores. Downregulation of OsAGO17 by artificial microRNA technology based on the endogenous osa-miRNA319a precursor was successfully achieved. It is found that downregulation of OsAGO17 could significantly affect pollen fertility and cause pollen abortion, thus suggesting that OsAGO17 functions in rice pollen development. In addition, the downregulation of OsAGO17 mainly caused a low seed-setting rate, thereby resulting in the reduction of grain yield, whereas the downregulation of OsAGO17 did not significantly affect rice vegetative growth and other agricultural traits including number of florets per panicle, number of primary branch per panicle, and 100-grain weight. Furthermore, the result of subcellular localization analysis indicated that the OsAGO17 protein was localized to both the nucleus and the cytoplasm. Conclusion: These results represent the first report of the biological function for OsAGO17 in rice and indicate that OsAGO17 may possibly play crucial regulatory roles in rice pollen development. It helps us to better understand the mechanism of pollen development in rice.

Impact of environmental changes on the reproductive biology in Pyrostegia venusta Presl.

Local environment (temperature and relative humidity) affects reproductive biology in Pyrostegia venusta (Bignoniaceae) growing at Agra and Mysore. At Agra, the species flowers profusely during December to March, but fails to bear fruits. At Mysore, on the other hand it flowers during November to February and produces well developed fruits with winged seeds. This species, growing at two places, exhibited differences in their pollen fertility and in vivo pollen germination. Pollen fertility at Agra and Mysore was 27.55 and 80-90%, respectively. The in vivo pollen germination on stigmatic surface was only 3-4% at Agra, but 85-95% at Mysore. The flowers at Agra also exhibited heterostyly and increased number of stamens and stigmatic lobes. The significantly low and wide ranged temperature (4.5-33.8oC) and between 23-98% RH during the flowering period at Agra could be the cause for reduced in pollen fertility, floral polymorphism and inhibition of pollen germination on the stigmatic surface and fruitlessness. At Mysore, where temperature ranges between 20.2-33.5oC and RH varies from 33-75% profuse fruiting takes place. The study shows a direct control of environment over the process of reproduction.