Role of SPA proteins in COP1 subcellular localization ($)

SPA (SUPPRESSOR OF PHYTOCHROME A-105) proteins form a complex with COP1  (CONSTITUTIVELY PHOTOMORPHOGENIC 1) and are required for COP1 to respond to changes in the light environment and transduce light signals and influence plant development. In this paper, Balcerowicz et al. investigated the importance of SPA proteins in the COP1/SPA complex. Using fluorescence, they could locate exactly where COP1 was in seedlings grown in light or kept in darkness, in a background with or without SPA proteins. Their results show that SPA proteins are not necessary for COP1 to localize in the nucleus but they are required for the complex to leave the nucleus after exposure to light, without affecting its degradation rate. Furthermore, they show that COP1 localization mediated by SPA proteins respond differently to different light wavelengths. Altogether, the results show that SPA proteins are necessary for COP1 responsiveness to changes in the light environment by altering its subcellular localization and, in consequence, the proper response of plants to light. (Review by Gaby Auge) Plant Physiology, 10.1104/pp.17.00488