Phytochrome A is the primary photoreceptor for mediating various far-red light-induced responses in higher plants. It has been found that the proteins governing this response, which include FAR-RED ELONGATED HYPOCOTYL3 (FHY3) and FAR-RED-IMPAIRED RESPONSE1 (FAR1), are a pair of homologous proteins sharing significant sequence homology to mutator-like transposases. These proteins appear to be novel transcription factors, which are essential for activating the expression of FHY1 and FHL (for FHY1-like) and related genes, whose products are required for light-induced phytochrome A nuclear accumulation and subsequent light responses in plants.The FRS (FAR1 Related Sequences) family of proteins share a similar domain structure to mutator-like transposases, including an N-terminal C2H2 zinc finger domain, a central putative core transposase domain, and a C-terminal SWIM motif (named after SWI2/SNF and MuDR transposases). It seems plausible that the FRS family represent transcription factors derived from mutator-like transposases [, ]. This entry represents a domain found in FAR1 and FRS proteins. It contains a WRKY like fold and is therefore most likely a zinc binding DNA-binding domain.
Exportin-5 mediates the nuclear export of proteins bearing a double-stranded RNA binding domain (dsRBD) and double-stranded RNAs (cargos) []. Exportin-5 yeast homologue, also known as Msn5, is involved in nuclear import of replication protein A and export of Far1 and transcription factors Swi5, Swi6, Msn2, and Pho4 [, , ]. Its Arabidopsis homologue, HASTY 1, is involved in the nuclear export of microRNAs (miRNAs) [].
This entry represents a group of plant and fungal proteins, including a number of Arbidopsis FHY3/FAR1-related proteins []. FHY3 (FAR-RED ELONGATED HYPOCOTYL3) and FAR1 (FAR-RED IMPAIRED RESPONSE1) are transcription factors derived from ancient transposases during evolution. They are involved in chlorophyll biosynthesis via the activation of HEMB1 gene expression []. They can also integrate light and abscisic acid signaling in Arabidopsis []and may have broad functions in plant growth and development [].
This entry includes exportin-1/5 from eukaryotes.Exportin-1, also known as CRM1, is a nuclear export receptor that have been shown to be involved in U3 snoRNA transport from Cajal bodies to nucleoli []. It also controls the composition of many nucleoplasmic complexes [].Exportin-5 mediates the nuclear export of proteins bearing a double-stranded RNA binding domain (dsRBD) and double-stranded RNAs (cargos) []. Exportin-5 yeast homologue, also known as Msn5, is involved in nuclear import of replication protein A and export of Far1 and transcription factors Swi5, Swi6, Msn2, and Pho4 [, , ]. Its Arabidopsis homologue, HASTY 1, is involved in the nuclear export of microRNAs (miRNAs) [].
This entry represents a group of plant proteins, including FHY1 (At2g37678) from Arabidopsis. Phytochrome A (phyA) is the photoreceptor in Arabidopsis that mediates the far-red light high radiance response. AtFHY1 is a key regulator of far red/red (FR/R) spectrum-specific responses by regulating phyA shuttling from the cytoplasm to the nucleus and by directly regulating the expression of some target genes. AtFHY1 phosphorylation is induced by the R signal, is part of the FR/R spectrum sensing mechanism that ensures its optimal response to specific light quality []. AtFHY1 also has an independent role in gene modulation and plant development under far-red light [].This entry also includes FHL (FHY1 Like). FHL is essential for light-regulated PHYA nuclear accumulation and subsequent PHYA phototropic signaling processes [, , ]. The transcription of FHY1 and FHL are controlled by FHY3 (Far-red elongated HYpocotyl 3) and FAR1 (FAr-red impaired Response 1), a related pair of transcription factors [].
