The microRNA (miRNA) miR396 regulates GROWTH-REGULATING FACTORs (GRFs), a plant 
specific family of transcription factors. Overexpression of miR396 causes a 
decrease in the GRFs that has been shown to affect cell proliferation in the 
meristem and developing leaves. To bring further insights into the function of 
the miR396 regulatory network we performed a mutant enhancer screen of a stable 
Arabidopsis transgenic line expressing 35S:miR396b, which has a reduction in 
leaf size. From this screen we recovered several mutants enhancing this 
phenotype and displaying organs with lotus- or needle-like shape. Analysis of 
these plants revealed mutations in as2 and rdr6. While 35S:miR396b in an as2 
context generated organs with lotus-like shape, the overexpression of the miRNA 
in an rdr6 mutant background caused more important developmental defects, 
including pin-like organs and lobed leaves. Combination of miR396 
overexpressors, and rdr6 and as2 mutants show additional organ defects, 
suggesting that the three pathways act in concert. Genetic interactions during 
leaf development were observed in a similar way between miR396 overexpression 
and mutants in RDR6, SGS3 or AGO7, which are known to participate in 
trans-acting siRNA (ta-siRNA) biogenesis. Furthermore, we found that miR396 can 
cause lotus- and pin-like organs per se, once a certain expression threshold is 
overcome. In good agreement, mutants accumulating high levels of TCP4, which 
induces miR396, interacted with the AS1/AS2 pathway to generate lotus-like 
organs. The results indicate that the miR396 regulatory network and the ta-siRNA 
biogenesis pathway synergistically interact during leaf development and 
morphogenesis.