The study investigates the role of Argonaute1 (AGO1) in the microRNA (miRNA) pathway and its regulation by the miRNA pathway in plant development. AGO1 is crucial for miRNA function, as *Arabidopsis ago1* mutants exhibit increased accumulation of mRNAs targeted for cleavage by miRNAs. In hypomorphic *ago1* alleles, this effect is observed without a significant change in miRNA levels, while in null alleles, it is accompanied by a drop in some miRNAs. The authors show that targeting of *AGO1* mRNA by miR168 is essential for proper plant development, demonstrating the importance of feedback control by this miRNA. Transgenic plants expressing a mutant *AGO1* mRNA with decreased complementarity to miR168 overaccumulate *AGO1* mRNA and exhibit developmental defects similar to those of *dcl1*, *hen1*, and *hy1* mutants. These defects can be rescued by expressing a compensatory miRNA complementary to the mutant *AGO1* mRNA, confirming the regulatory relationship between miR168 and its target. The findings highlight the importance of AGO1 in the miRNA pathway and the role of negative feedback regulation in plant development.The study investigates the role of Argonaute1 (AGO1) in the microRNA (miRNA) pathway and its regulation by the miRNA pathway in plant development. AGO1 is crucial for miRNA function, as *Arabidopsis ago1* mutants exhibit increased accumulation of mRNAs targeted for cleavage by miRNAs. In hypomorphic *ago1* alleles, this effect is observed without a significant change in miRNA levels, while in null alleles, it is accompanied by a drop in some miRNAs. The authors show that targeting of *AGO1* mRNA by miR168 is essential for proper plant development, demonstrating the importance of feedback control by this miRNA. Transgenic plants expressing a mutant *AGO1* mRNA with decreased complementarity to miR168 overaccumulate *AGO1* mRNA and exhibit developmental defects similar to those of *dcl1*, *hen1*, and *hy1* mutants. These defects can be rescued by expressing a compensatory miRNA complementary to the mutant *AGO1* mRNA, confirming the regulatory relationship between miR168 and its target. The findings highlight the importance of AGO1 in the miRNA pathway and the role of negative feedback regulation in plant development.