ALTERED MERISTEM PROGRAM1 regulates leaf identity independently of miR156-mediated translational repression

Abstract

In Arabidopsis, loss of the carboxypeptidase ALTERED MERISTEM PROGRAM1 (AMP1) produces an increase in the rate of leaf initiation, an enlarged shoot apical meristem and an increase in the number of juvenile leaves. This phenotype is also observed in plants with reduced levels of miR156-targeted SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) transcription factors, suggesting that AMP1 might promote SPL activity. However, we found that the amp1 mutant phenotype is only partially corrected by elevated SPL gene expression, and that amp1 has no significant effect on SPL transcript levels, or on the level or the activity of miR156. Although AMP1 has been reported to promote miRNA-mediated translational repression, amp1 did not prevent the translational repression of the miR156 target SPL9 or the miR159 target MYB33. These results suggest that AMP1 regulates vegetative phase change downstream of, or in parallel to, the miR156/SPL pathway, and that it is not universally required for miRNA-mediated translational repression.

AMP1 and CYP78A5/7 act through a common pathway to govern cell fate maintenance in Arabidopsis thaliana

“…One possible explanation for this discrepancy might be that release of translational repression of miRNA targets is restricted to the AMP1/LAMP1 expression domain and/or affects only a subset of miRNA targets with a role in embryo and SAM patterning. The latter is supported by a recent study, in which no translational de-repression of miR156 target SPL9 or the miR159 target MYB33 could be observed in amp1 [41]. We showed that AMP1 acts through the AP2 transcription factor RAP2.6L, which is controlled by the miRNA-regulated HD-ZIP III proteins [22] and we are currently analyzing the functional relationship between HD-ZIP III mis-regulation and amp1 phenotypes.…”

Temporal regulation of vegetative phase change in plants

“…In Arabidopsis, miR156/157 regulate the expression of 10 SPL genes 51,83,92 through a combination of transcript cleavage 94,95 and translational repression 96,97 , with translational repression being the dominant mechanism 52 . A recent genetic analysis suggests the cellular site of translational repression by miR156 may differ from that of other miRNAs 98 . Some of the effects of the miR156/SPL module are mediated by miR172.…”

Biogenesis, Trafficking, and Function of Small RNAs in Plants

“…Interestingly, it is generally believed that miRNA-mediated translational repression requires AMP1 gene, while siRNA-mediated translational repression does not require AMP1 gene ( Wu et al, 2020 ; Yang et al, 2021a ). However, recent studies have shown that AMP1 does not prevent translational repression of the SPL9 gene (target of miR156) or MYB33 gene (target of miR159), suggesting that AMP1 is not universally required for miRNA-mediated translational repression ( Fouracre et al, 2020 ). In addition, sRNAs play an important role in the regulation of diverse plant phytohormones by controlling key factors involved in translational repression ( Li et al, 2020 ).…”