![]() ![]() They delimit organ boundaries for proper growth control floral meristem development ovule development and male germ cell division. They regulate plant height spikelet architecture flowering time root hair development shoot branching and secondary metabolite biosynthesis. The EAR repressome is involved in a wide range of functions in plants, from development to stress responses. Comparatively, LxLxL motif occurs at a higher frequency in different plant species. The ERF–EAR motif contributes about 86% of the total plant repressome in Arabidopsis. TLLLFR, KLFGV, ethylene-responsive element binding factor-associated amphiphilic repression (EAR), and NAC-associated repression domain (NARD) are common plant repression motifs. Active repressors have an intrinsic repression motif which interacts with the general transcription factors (TFs) or with other chromatin components, eventually inhibiting the binding of transcriptional activators. Transcriptional repressors act either in an active or passive manner. Regulation of gene expression is an interesting phenomenon with the participation of multiple players, some of which act as repressors of downstream genes and regulate their spatio-temporal expression pattern. The study reports a straightforward assay to analyze repressor activity, along with the identification of a strong DLN repressor from rice. Comparatively, rice has more DLN repressor encoding genes than Arabidopsis, and DLNSPP motif from rice is 40% stronger than the known Arabidopsis SRDX motif. ![]() The DLN hexapeptide motif is essential for repression, and at least two “DLN” residues cause maximal repression. We have designed a simple yeast-based experiment wherein a DLN motif can successfully cause strong repression of downstream reporter genes, when fused to a transcriptional activator of rice or yeast. Most of the DLN repressome proteins have a single DLN motif, with higher relative percentage in the C-terminal region. Apart from DLNxxP motif conservation, DLNxP and DLNxxxP motifs with variable numbers/positions of proline and those without any proline conservation have been identified. In rice ( Oryza sativa), we have identified a total of 266 DLN repressor proteins, with the former motif and its modifications thereof comprising 227 transcription factors and 39 transcriptional regulators. They contain either DLNxxP or LxLxL as the identifying hexapeptide motif. In plants, a well-established class of repressors are proteins with an ERF-associated amphiphilic repression/EAR domain. This upregulation of nitrogen transporter and nitrogen assimilation-related genes might confer tolerance to nitrogen deficiency in 35S:GATA4-SRDX plants.Transcriptional regulation includes both activation and repression of downstream genes. Under nitrogen-deficient conditions, the expression of genes for cytosolic glutamine synthetases was upregulated in shoots of 35S:GATA4-SRDX plants compared with wild type. The expression levels of NITRATE TRANSPORTER 2.1, ASPARAGINE SYNTHETASE and NITRATE REDUCTASE 1 were significantly higher in roots of 35S:GATA4-SRDX plants than in wild type under nitrogen-sufficient conditions. 35S:GATA4-SRDX plants exhibited shorter primary roots, fewer lateral roots, and higher root hair density compared with wild type. ![]() 35S:GATA4-SRDX seedlings were significantly larger than wild type under nitrogen-sufficient and -deficient conditions (10 and 0.5 mM NH 4NO 3, respectively). Here, we report that the expression of the chimeric repressor for the GATA4 transcription factor ( 35S:GATA4-SRDX) improved tolerance to nitrogen deficiency in Arabidopsis thaliana. Increasing nitrogen use efficiency in plants may help overcome these problems and is, therefore, an important and active subject of agricultural research. Nitrogen limits crop yield, but application of nitrogen fertilizer can cause environmental problems and much fertilizer is lost without being absorbed by plants. ![]()
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