ARF5/MONOPTEROS directly regulates miR390 expression in the Arabidopsis thaliana primary root meristem.

The root meristem is organized around a quiescent center (QC) surrounded by stem cells that generate all cell types of the root. In the transit-amplifying compartment, progeny of stem cells further divides prior to differentiation. Auxin controls the size of this transit-amplifying compartment via auxin response factors (ARFs) that interact with auxin response elements (AuxREs) in the promoter of their targets. The microRNA miR390 regulates abundance of ARF2, ARF3, and ARF4 by triggering the production of trans-acting (ta)-siRNA from the TAS3 precursor. This miR390/TAS3/ARF regulatory module confers sensitivity and robustness to auxin responses in diverse developmental contexts and organisms. Here, we show that miR390 is expressed in the transit-amplifying compartment of the root meristem where it modulates response to exogenous auxin. We show that a single AuxRE located in miR390 promoter is necessary for miR390 expression in this compartment and identify that ARF5/MONOPTEROS (MP) binds miR390 promoter via the AuxRE. We show that interfering with ARF5/MP-dependent auxin signaling attenuates miR390 expression in the transit-amplifying compartment of the root meristem. Our results show that ARF5/MP regulates directly the expression of miR390 in the root meristem. We propose that ARF5, miR390, and the ta-siRNAs-regulated ARFs modulate the response of the transit-amplifying region of the meristem to exogenous auxin.

Transcript and proteome analysis reveals reduced expression of calgranulins in head and neck squamous cell carcinoma.

The calcium-binding proteins of the S100 and the annexin protein families have been implicated in a variety of important physiological functions including membrane remodeling, calcium-related intracellular signaling, cytoskeleton dynamics, tissue homeostasis, and formation of the cornified envelope in differentiating keratinocytes. Deregulated expression of members of these families has been reported in different types of neoplasia and other diseases, but the results were not consistent. Here we have applied a combination of cDNA microarrays, quantitative reverse transcriptase-PCR (qRT-PCR) and surface enhanced laser desorption ionisation-time of flight mass spectrometry (SELDI-TOF MS) to study differential expression of these genes in head and neck squamous cell carcinoma (HNSCC). The calgranulins A and B and annexins 1 and 2 were found to be down-regulated in HNSCC, compared with normal mucosa, at both the mRNA and protein level. Upon validation of the differential gene expression by tissue microarray immunohistochemistry, we detected novel expression patterns of calgranulins A and B both in normal mucosa as well as in HNSCC. In contrast to squamous cancer of skin and other cancers in which the calgranulins were found to be up-regulated, most HNSCC showed reduced and widely deranged staining patterns including heterogeneous nuclear, cytoplasmic and membranous staining, and even enhanced staining in the tumor stroma. These observations suggest that the normal function of the calgranulins A and B in mucosa might be different from that in skin.