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CURLY LEAF Regulates MicroRNA Activity by Controlling ARGONAUTE 1 Degradation in Plants

Author:
Ré, Delfina A., Cambiagno, Damian A., Arce, Agustin L., Tomassi, Ariel H., Giustozzi, Marisol, Casati, Paula, Ariel, Federico D., Manavella, Pablo A.
Source:
Molecular plant 2020 v.13 no.1 pp. 72-87
ISSN:
1674-2052
Subject:
alleles, leaves, methyltransferases, microRNA, mutants, tissues, ubiquitination, ultraviolet radiation
Abstract:
CURLY LEAF (CLF) encodes the methyltransferase subunit of the Polycomb Repressor Complex 2 (PRC2), which regulates the expression of target genes through H3K27 trimethylation. We isolated a new CLF mutant allele (clf-78) using a genetic screen designed to identify microRNA (miRNA) deficient mutants. CLF mutant plants showed impaired miRNA activity caused by increased ubiquitination and enhanced degradation of ARGONAUTE 1 (AGO1) in specific tissues. Such CLF-mediated AGO1 regulation was evident when plants were exposed to UV radiation, which caused increased susceptibility of clf mutants to some UV-induced responses. Furthermore, we showed that CLF directly regulates FBW2, which in turn triggers AGO1 degradation in the clf mutants. Interestingly, AGO1 bound to a target appeared particularly prone to degradation in the mutant plants, a process that was exacerbated when the complex bound a non-cleavable target. Thus, prolonged AGO1–target interaction seems to favor AGO1 degradation, suggesting that non-cleavable miRNA targets may overcome translation inhibition by modulating AGO1 stability in plants.
Agid:
6723203