Diethyl Ether Anaesthesia Inhibits De‐etiolation of Barley Seedlings by Locking Them in Intermediate Skoto‐photomorphogenetic State

Light is an essential environmental signal for plant development called photomorphogenesis. Here, we show that diethyl ether anaesthesia inhibits the de-etiolation process in barley (Hordeum vulgare) seedlings. Illuminated seedlings exposed to diethyl ether accumulated significantly less chlorophylls and chlorophyll-binding proteins, and exhibited reduced maximum quantum yield of photosystem II photochemistry (Fv/Fm). Although the direct effect of light necessary for the greening process, i.e. for the photoreduction of protochlorophyllide (Pchlide) to chlorophyllide (Chlide) catalysed by light-dependent protochlorophyllide oxidoreductase A (PORA), 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 attenuated. On the other hand, transcription of chloroplast-encoded genes was not negatively affected by diethyl ether treatment during greening. Among the genes negatively regulated by light, PORA and PHYA were only slightly affected by diethyl ether. 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 effects on greening: i) it inhibited the expression of PhANGs and chlorophyll biosynthesis-related genes irrespective of light conditions, ii) it blocked the light-induced expression of these genes and greening process of etiolated seedlings. Our study indicates that diethyl ether affects plastid biogenesis, which alters the orchestration of negative and positive regulators affecting phytochrome and/or retrograde signalling and does not allow expression of PhANGs. Thus, the plants are locked in an intermediate skoto-photomorphogenetic state in the light.