High impact information on SPA1

• SPA1 can localize to the nucleus, suggesting a possible function in phytochrome A-specific regulation of gene expression [1].
• SPA1, a WD-repeat protein specific to phytochrome A signal transduction [1].
• Here we report that COP1 acts as part of a large protein complex and interacts with SPA1 in a light-dependent manner [2].
• These results indicate that phyA is necessary in a non-allele-specific fashion for the expression of the spa1 mutant phenotype and that phyB to phyE are not sufficient for this effect [3].
• Mutations in SPA1 cause phyA-independent early flowering under short day (SD) but not long day (LD) conditions, and this phenotype is enhanced by additional loss of SPA3 and SPA4 function [4].

Biological context of SPA1

• Taken together, the analysis of SPA transcript levels suggests that differences in SPA gene expression patterns contribute to divergence in SPA1-SPA4 function [5].
• SPA1: a new genetic locus involved in phytochrome A-specific signal transduction [3].
• Here, we show that SPA1 is involved in regulating circadian rhythms and flowering time in plants [6].
• The up-regulation of SUPPRESSOR OF PHYTOCHROME A RESPONSES 1 (SPA1) and CONSTITUTIVE PHOTOMORPHOGENIC 1-like (COP1-like) genes suggests that the PHYA-mediated pathway was attenuated by red light [7].

Anatomical context of SPA1

• The action of SPA1 persisted for approximately 2 d of red light, a period well beyond the time when the phyA photoreceptor and its influence on growth have both decayed to undetectable levels [8].

Physical interactions of SPA1

• We show that SPA1 physically interacts with HFR1 in a yeast two-hybrid assay and an in vitro co-immunoprecipitation assay [9].

Other interactions of SPA1

• Here we show that overexpression of Arabidopsis SPA1 results in a hyperetiolation phenotype and reduced accumulation of HY5 and HFR1 [10].
• Arabidopsis suppressor of phyA-105 (SPA1), which encodes a protein structurally related to COP1, also acts to repress photomorphogenesis under various light conditions [10].
• In light-grown seedlings and adult plants, in contrast, SPA1 function is divergent from SPA2 function, with SPA1 playing the predominant role [5].
• We show that SPA1 represses not only red, far-red and blue light responses in a PHYA-dependent fashion, but also acts to suppress light signaling in darkness [5].
• These results indicate that EID1 and SPA1 are involved in different but interacting phyA-dependent signal transduction chains [11].

References