Considered together, our data indicate that OsPIL11 and OsPIL16 primarily function as transcriptional activators, at least in regards to promoting skotomorphogenesis and repressing the expression of photosynthesis-related genes. In contrast, the expression levels of these photosynthesis-related genes were down-regulated in dark-grown transgenic seedlings overexpressing OsPIL11 or OsPIL16, which had exaggerated skotomorphogenesis. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analyses indicated that the expression levels of genes related to photosynthesis, photosynthesis–antenna proteins, and porphyrin and chlorophyll metabolism were up-regulated in the dark-grown OsPIL11-SRDX and OsPIL16-SRDX lines, whereas the expression of genes related to the auxin pathway was down-regulated. The results of an RNA sequencing analysis revealed that the dark-grown OsPIL11-SRDX and OsPIL16-SRDX lines had gene expression patterns similar to those of wild-type seedlings grown under red light. The OsPIL11-SRDX and OsPIL16-SRDX seedlings grown in darkness had constitutively photomorphogenic phenotypes with short coleoptiles and open leaf blades. In the present study, to explore the functions of PILs in rice skotomorphogenesis, we generated OsPIL11-SRDX and OsPIL16-SRDX transgenic lines by fusing the SRDX transcriptional repressor motif to the C-terminal of two members of the phytochrome interacting factor-like (OsPIL) family in rice (OsPIL11 and OsPIL16).
#SRDX DOMAIN ACTIVATOR#
It has been reported that SRDX motif, LDLDLELRLGFA, was able to convert a transcriptional activator into a strong repressor. Because of the development of rice direct seeding cultivation systems, there is an increasing need for clarifying the molecular mechanism underlying rice skotomorphogenic development. These results indicate that BHB3 might play an important role not only to the BR signaling but also the regulation of greenings.ĭark-grown seedlings develop skotomorphogenesis. We found that BHB3 contains three motifs similar to the conserved EAR-repression domain, suggesting that BHB3 may act as a transcriptional repressor. Interestingly, both BHB3-sx and BHB3-ox showed pale green phenotype, in which the expression of genes related photosynthesis and chlorophyll contents were significantly decreased. Interestingly, ectopic expression of BHB3 (BHB3-ox) also repressed the BR inducible genes and shorten hypocotyl that would be similar to a BR-deficient phenotype. Here, we identified a homeobox-leucine zipper type transcription factor, BRASSINOSTEROID-RELATED-HOMEOBOX 3 (BHB3), of which a chimeric repressor expressing plants (BHB3-sx) significantly downregulated the expression of BAS1 and SAUR-AC1 that are BR inducible genes. To identify novel transcription factors that may be involved in unknown mechanisms of BR signaling, we screened the chimeric repressor expressing plants (CRES-T), in which transcription factors were converted into chimeric repressors by the fusion of SRDX plant-specific repression domain, to identify those that affect the expression of BR inducible genes. Thus, it should be useful not only for the rapid analysis of the functions of redundant plant transcription factors but also for the manipulation of plant traits via the suppression of gene expression that is regulated by specific transcription factors.īrassinosteroid (BR) is a phytohormone that acts as important regulator of plant growth. This chimeric repressor silencing technology (CRES-T), exploiting the EAR-motif repression domain, is simple and effective and can overcome genetic redundancy. Chimeric EIN3, CUC1, PAP1, and AtMYB23 repressors that included the EAR motif dominantly suppressed the expression of their target genes and caused insensitivity to ethylene, cup-shaped cotyledons, reduction in the accumulation of anthocyanin, and absence of trichomes, respectively. We show here that four different transcription factors fused to the EAR motif, a repression domain of only 12 amino acids, act as dominant repressors in transgenic Arabidopsis and suppress the expression of specific target genes, even in the presence of the redundant transcription factors, with resultant dominant loss-of-function phenotypes. The redundancy of genes for plant transcription factors often interferes with efforts to identify the biologic functions of such factors.
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