[Expression and function of AOX1 gene family during the greening of etiolated rice seedlings].

Under constant light, increases in V(t) (total respiration rate), V(alt) (capacity of alternative pathway), and V(alt)/V(t) ration values (Figs.1-3) in fully etiolated rice seedlings leaves were founded. Northern hybridization with special probes for rice AOX1a, AOX1b and AOX1c revealed that the AOX1c mRNA was mainly present under constant light (Fig.4). SHAM (salicylhydroxamic acid) decreased the relative oxygen evolution rate and chlorophyll content during the rapid greening of the etiolated rice seedlings (Figs.6, 7). We found that illumination caused bigger increase in V(alt) in fully etiolated rice seedlings than in any partially etiolated rice seedlings (Fig.8A), while the soluble sugar contents did not show any significant differences (Fig.8B). This revealed the connection between greening process and cyanide-resistant respiration in rice seedlings. We infer that one of the possible functions of the cyanide-resistant respiration is to maintain a high rate of respiratory electron transport for the essential biosynthesis processes at the early stage of chloroplast development. Cyanide-resistant respiration may provide a regulatory mechanism for the balance between the requirements of the energy and substances.