Short answers, pulled from the story.
LUX encodes a protein called LUX ARRHYTHMO that is necessary for circadian rhythms in Arabidopsis thaliana. The LUX protein joins with ELF3 and ELF4 to form the Evening Complex, which represses transcription of clock genes including PRR9 to keep the plant's daily biological clock running. Plants with null mutations in LUX become arrhythmic and lose the ability to sustain regular circadian oscillations.
LUX was first sequenced in 2000 by a team at the Plant Gene Expression Center at UC Berkeley as part of the Arabidopsis Genome Initiative. Evidence that LUX is necessary for circadian rhythms came later, in 2005, from researchers at the Center for Gene Research at Nagoya University and the Steve Kay lab at the Scripps Research Institute.
The Evening Complex is a three-protein assembly consisting of LUX ARRHYTHMO, Early Flowering 3 (ELF3), and Early Flowering 4 (ELF4). It is expressed during the evening and acts as a transcriptional repressor, silencing the PRR9 gene that codes for a component of the Midday Complex. The Evening Complex is a core component of the Arabidopsis repressilator model of the circadian clock.
LUX mutants cannot repress Phytochrome Interacting Factor 4 (PIF4) and Phytochrome Interacting Factor 5 (PIF5) during the evening. Those transcription factors accumulate prematurely and drive excess growth during the night, resulting in an abnormally elongated hypocotyl phenotype.
NOX, also called BROTHER OF LUX ARRHYTHMO (BOA), is a related Myb-like GARP transcription factor that peaks in the late evening and can interact with ELF4. Unlike LUX, NOX is not essential for circadian rhythms; RNA interference knockouts of NOX still produced oscillating plants, while LUX null mutants are arrhythmic.
Yes. STERILE NODES (SN) in peas (Pisum sativum) and HvLUX1 in barley (Hordeum vulgare) are both orthologs of LUX. Two orthologs, ROC15 and ROC75, have also been found in the alga Chlamydomonas reinhardtii, though it is unknown whether those species assemble a functional complex equivalent to the Arabidopsis Evening Complex.