Synergistic interactions between the ta-siRNA pathways and the miR396 network

MECCHIA, M.A.; DEBERNARDI, J.M; RODRIGUEZ, R.E.; BRESSO, E.G.; SCHOMMER, C.; PALATNIK, J.F.

MECHANISMS OF DEVELOPMENT

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2013 vol. 130 p. 2 - 13

0925-4773

The microRNA (miRNA) miR396 regulates GROWTH-REGULATING FACTORs (GRFs), a plantspecific family of transcription factors. Overexpression of miR396 causes a decrease inthe GRFs that has been shown to affect cell proliferation in the meristem and developingleaves. To bring further insights into the function of the miR396 regulatory network we performeda mutant enhancer screen of a stable Arabidopsis transgenic line expressing35S:miR396b, which has a reduction in leaf size. From this screen we recovered severalmutants 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 as2context generated organs with lotus-like shape, the overexpression of the miRNA in anrdr6 mutant background caused more important developmental defects, including pin-likeorgans and lobed leaves. Combination of miR396 overexpressors, and rdr6 and as2 mutantsshow additional organ defects, suggesting that the three pathways act in concert. Geneticinteractions during leaf development were observed in a similar way between miR396 overexpressionand mutants in RDR6, SGS3 or AGO7, which are known to participate in transactingsiRNA (ta-siRNA) biogenesis. Furthermore, we found that miR396 can cause lotusandpin-like organs per se, once a certain expression threshold is overcome. In good agreement,mutants accumulating high levels of TCP4, which induces miR396, interacted withthe AS1/AS2 pathway to generate lotus-like organs. The results indicate that the miR396regulatory network and the ta-siRNA biogenesis pathway synergistically interact duringleaf development and morphogenesis.