Diethyl ether anaesthesia inhibits de-etiolation of barley (Hordeum vulgare) seedlings

Light is an essential environmental signal for plant development called photomorphogenesis. Here we showed that diethyl ether anaesthesia inhibited de-etiolation process in barley (Hordeum vulgare) seedlings. Illuminated seedlings exposed to diethyl ether accumulated significantly less chlorophylls, chlorophyll-binding proteins and exhibited reduced maximum quantum yield of photosystem II photochemistry (Fv/Fm). Although direct effect of light necessary for greening process, i.e. photoreduction of protochlorophyllide (Pchlide) to chlorophyllide (Chlide) catalysed by light-dependent protochlorophyllide oxidoreductase (POR), was not inhibited, the RNA-seq and qPCR analyses showed that light-induced expression of photosynthesis-associated nuclear genes (PhANGs) and genes encoding enzymes for chlorophyll biosynthesis were blocked. On the other hand, transcription of chloroplast-encoded genes psbA and psbB, encoding D1 and CP47 proteins, respectively, were not negatively affected by diethyl ether treatment during greening. Among the genes negatively regulated by light, the PORA and PHYA were only slightly affected. The effect of diethyl ether was fully reversible and after its removal, the greening process was fully restored. Our data indicate that diethyl ether had two fold effect on greening: i) it inhibited expression of PhANGs and chlorophyll biosynthesis-related genes irrespective of light conditions, ii) it also blocked light-induced de-repression of these genes and greening process of etiolated seedlings. Our study indicates that diethyl ether alters orchestration of negative and positive regulators affecting phytochrome and/or retrograde signalling and does not allow de-repression of PhANGs and thus the plants are locked in intermediate skoto-photomorphogenetic state in the light.