AUTHOR=Hills Alison C. , Khan Safina , López-Juez Enrique 

TITLE=Chloroplast Biogenesis-Associated Nuclear Genes: Control by Plastid Signals Evolved Prior to Their Regulation as Part of Photomorphogenesis

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 6 - 2015

YEAR=2015

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2015.01078

DOI=10.3389/fpls.2015.01078

ISSN=1664-462X

ABSTRACT=The assembly of photosynthetically-competent chloroplasts occurs in angiosperm seedlings when first exposed to light, and is due to the control by light of photosynthesis-associated nuclear genes (PhANGs), also dependent upon plastid-to-nucleus “biogenic” communication signals. The relationship between light- and plastid signal-regulation of PhANGs is close but poorly understood. In contrast, many conifers green in the dark and the promoter of a pine PhANG, Lhcb, is active in the dark in tobacco. Here we show that the activity of this promoter in tobacco is sensitive to plastid photobleaching, or to the inhibition of plastid translation in the light or the dark, and the same interventions reduce expression of the native gene in pine seedlings, demonstrating classic plastid biogenic signalling in gymnosperms. Furthermore, Arabidopsis mutations causing defective plastid biogenesis suppress the effect in darkness of mutations in COP1 and DET1, repressors of photomorphogenesis, for the expression of several PhANGs but not a photosynthesis-unrelated, light-regulated gene. GLK transcriptional regulators mediate the response of LHCB but not of other tested PhANGs. We propose gain of the ability by repressors of photomorphogenesis to suppress the response of PhANG promoters to positive plastid biogenic signals in the dark to have contributed to the evolution of light control of chloroplast biogenesis.