Peptide aptamers are artificial short peptides that potentially interfere with 
the biological roles of their target proteins; however, this technology has not 
yet been applied to plant functional genomics. MAGO and Y14, the two core 
subunits of the exon junction complex (EJC), form obligate heterodimers in 
eukaryotes. In Oryza sativa L. (rice), each of the two genes has two homologs, 
designated OsMAGO1 and OsMAGO2, and OsY14a and OsY14b, respectively. Here, we 
characterized a 16-amino acida peptide aptamer (PAP) for the rice MAGO proteins. 
PAP and rice Y14 bound competitively to rice MAGO proteins. Specifically 
targeting the MAGO proteins by expressing the aptamer in transgenic rice plants 
did not affect the endogenous synthesis and accumulation of MAGO proteins; 
however, the phenotypic variations observed in multiple organs phenocopied those 
of transgenic rice plants harboring RNA interference (RNAi) constructs in which 
the accumulation of MAGO and/or OsY14a transcripts and MAGO proteins was 
downregulated severely. Morphologically, the aptamer transgenic plants were 
short with abnormally developed flowers, and the stamens exhibited reduced 
degradation and absorption of both the endothecium and tapetum, thus confirming 
that EJC core heterodimers play essential roles in rice development, growth and 
reproduction. This study reveals that as a complementary approach of RNAi, 
peptide aptamers are powerful tools for interfering with the function of 
proteins in higher plants.