EARLY FLOWERING 4Functions in Phytochrome B-Regulated Seedling De-Etiolation

Abstract

To define the functions of genes previously identified by expression profiling as being rapidly light induced under phytochrome (phy) control, we are investigating the seedling de-etiolation phenotypes of mutants carrying T-DNA insertional disruptions at these loci. Mutants at one such locus displayed reduced responsiveness to continuous red, but not continuous far-red light, suggesting a role in phyB signaling but not phyA signaling. Consistent with such a role, expression of this gene is induced by continuous red light in wild-type seedlings, but the level of induction is strongly reduced in phyB-null mutants. The locus encodes a novel protein that we show localizes to the nucleus, thus suggesting a function in light-regulated gene expression. Recently, this locus was identified as EARLY FLOWERING 4, a gene implicated in floral induction and regulating the expression of the gene CIRCADIAN CLOCK-ASSOCIATED 1. Together with these previous data, our findings suggest that EARLY FLOWERING 4 functions as a signaling intermediate in phy-regulated gene expression involved in promotion of seedling de-etiolation, circadian clock function, and photoperiod perception.

ELF4Is Required for Oscillatory Properties of the Circadian Clock

“…1A). We thus confirm previous work by the Quail group (Khanna et al, 2003). Interestingly, ELF4-ox lines were indistinguishable from wild type under these assay conditions.…”

“…However, signaling through light input pathways in plants is itself a clock-controlled process, being gated by so-called zeitnehmer functions, one of which requires ELF3 (McWatters et al, 2000). Previous reports on ELF4 characterization have supported ELF4 action in a phytochrome B-dependent pathway of red-light perception (Khanna et al, 2003). Accordingly, we tested elf4-1 mutants and ELF4 overexpression (ELF4-ox) lines for alterations in detecting light input signals and/or diurnal processing of information (ELF4-ox construction is described below).…”

“…Here, ELF4 has been implicated in phytochrome B signaling because elf4 seedlings are hyposensitive to red light and ELF4 mRNA levels are low in the phyB mutant. Further, it has been interpreted that ELF4 controls red-light repression of hypocotyl elongation (Khanna et al, 2003) and that ELF4, together with TOC1, plays a major role in phytochrome-mediated input to the clock (Kikis et al, 2005). The early flowering behavior of elf4 is accompanied by misregulation of the flowering activator CONSTANS (CO), implying ELF4 acts on flowering time by regulating expression of CO (Doyle et al, 2002).…”

Conservation and Divergence of Circadian Clock Operation in a Stress-Inducible Crassulacean Acid Metabolism Species Reveals Clock Compensation against Stress

“…1C). The ELF4 genes encode very small, nuclear localized proteins of around 110 amino acid residues with no known functional domains (Doyle et al, 2002;Khanna et al, 2003). Only 22 residues are identical between all of the available ELF4 and ELF4-like sequences.…”

EARLY FLOWERING3 Redundancy Fine-Tunes Photoperiod Sensitivity

“…In legumes, however, NOX genes are not present, and a null mutant for the single LUX ortholog in pea, SN, has a very strong early flowering phenotype and is completely insensitive to photoperiod (Liew et al, 2014), similar to the double ELF3 mutant hr ppd. Arabidopsis ELF4 is a member of a small gene family (Khanna et al, 2003) in which the closest paralog, ELF4-LIKE1 (EFL1), appears also to have ELF4 activity but three other ELF4-like genes do not (Kolmos et al, 2009). In legumes, ELF4 is also represented by small gene family (Liew et al, 2009), and the fact that in pea an apparent null mutant for the ELF4 ortholog DNE has only a minor effect on flowering when the other EC genes are intact (Liew et al, 2014) again implies a probable redundancy with one or more other members of the family.…”