Interaction between Two Timing MicroRNAs Controls Trichome Distribution in Arabidopsis

Abstract

The miR156-targeted SQUAMOSA PROMOTER BINDING PROTEIN LIKE (SPL) transcription factors function as an endogenous age cue in regulating plant phase transition and phase-dependent morphogenesis, but the control of SPL output remains poorly understood. In Arabidopsis thaliana the spatial pattern of trichome is a hallmark of phase transition and governed by SPLs. Here, by dissecting the regulatory network controlling trichome formation on stem, we show that the miR171-targeted LOST MERISTEMS 1 (LOM1), LOM2 and LOM3, encoding GRAS family members previously known to maintain meristem cell polarity, are involved in regulating the SPL activity. Reduced LOM abundance by overexpression of miR171 led to decreased trichome density on stems and floral organs, and conversely, constitutive expression of the miR171-resistant LOM (rLOM) genes promoted trichome production, indicating that LOMs enhance trichome initiation at reproductive stage. Genetic analysis demonstrated LOMs shaping trichome distribution is dependent on SPLs, which positively regulate trichome repressor genes TRICHOMELESS 1 (TCL1) and TRIPTYCHON (TRY). Physical interaction between the N-terminus of LOMs and SPLs underpins the repression of SPL activity. Importantly, other growth and developmental events, such as flowering, are also modulated by LOM-SPL interaction, indicating a broad effect of the LOM-SPL interplay. Furthermore, we provide evidence that MIR171 gene expression is regulated by its targeted LOMs, forming a homeostatic feedback loop. Our data uncover an antagonistic interplay between the two timing miRNAs in controlling plant growth, phase transition and morphogenesis through direct interaction of their targets.

Grapevine Leafroll Disease and Associated Viruses: A Unique Pathosystem

“…Although this study provided a snapshot of Vvi-miRNA levels at a specific stage of the disease, additional studies are necessary to establish functional relevance of the regulation of Vvi-miRNA expression in disease biology. This is essential because diverse miRNAs are implicated in different plant developmental processes (14), and some miRNAs are known to either coregulate or coordinately regulate multiple biological functions in plants (146). Moreover, the differential regulation of virus-responsive plant miRNAs and the miRNA-mRNA interactome upon viral infection appears to vary between plant species and different tissue and cell types of an infected plant and to be dependent upon specific virus-host interactions, viral strain, and single versus coinfections of disparate viruses (147 and references therein).…”

The role of small RNAs in vegetative shoot development

“…The transcriptional targets of SPL9 include the flowering time genes miR172B [51] and SUPPRESSOR OF OVEREXPRESSION OF CO1 [43], and TRICHOMELESS1 and TRIPTYCHON [40], both of which repress trichome development in the inflorescence stem. In addition, a considerable degree of SPL9 activity is dependent on protein-protein interactions with a diverse range of other proteins [45,52**–55]. …”

Cleavage of INDOLE-3-ACETIC ACID INDUCIBLE28 mRNA by MicroRNA847 Upregulates Auxin Signaling to Modulate Cell Proliferation and Lateral Organ Growth in Arabidopsis

“…The expression of miR164 in root targets NAC1 mRNA for cleavage to downregulate auxin signals for lateral root development (Guo et al, 2005), whereas the expression of miR164 in inflorescences targets CUC1/2 to regulate the establishment and maintenance of the shoot apical and axillary meristems and floral boundary formation (Laufs et al, 2004;Mallory et al, 2004;Baker et al, 2005). A recent study shows that miR156 also functions antagonistically with miR171 in regulating trichome distribution in Arabidopsis (Xue et al, 2014).…”