Influence of irradiation on cyanide-resistant respiration and AOX1 multi-gene family expression during greening of etiolated rice seedlings

Abstract

We investigated the differential expression of AOX1 multi-gene family and the regulation of alternative respiratory pathway during initial greening development in leaves of rice (Oryza sativa L.) seedlings. After exposing the darkgrown rice seedlings to continuous irradiation, total respiration (V t ), capacity of alternative pathway (V alt ), and their ratio (V alt /V t ) increased with the greening of leaves. In this process, AOX1c transcript increased under constant irradiation, while AOX1a and AOX1b transcripts were hardly detected. Thus AOX1c in rice presents a similar expression pattern as AOX2 does in many dicotyledonous species during greening development. Compared with the rapid increase of cyanideresistant respiration in the presence of photon energy, CO 2 fixation was not observed until 8 h after the onset of irradiation. The AOX inhibitor salicylhydroxamic acid (SHAM; 1 mM) inhibited 67.3 % of cyanide-insensitive oxygen uptake in dark-grown leaves and 69.4 % of it in leaves grown under irradiation. Dark-grown plants pre-treated with SHAM were then irradiated for 12 h. SHAM did not obviously modify photosynthetic CO 2 fixation rate on a chlorophyll (Chl) content basis in both leaves and simultaneously isolated chloroplasts. Hence during initial greening steps of the plants, the induction of alternative pathway and AOX1 expression by irradiation is not directly linked with carbon assimilation of photosynthesis. The application of SHAM partially limited Chl production in rapidly greening leaves, indicating that Chl synthesis in the process of greening might be medicated to some extent by alternative respiratory pathway.

Effects of light on cyanide‐resistant respiration and alternative oxidase function in Arabidopsis seedlings

“…9). The CO 2 fixation rate was still undetectable in both aox1a and wild‐type etiolated leaves (Lurie 1977; Feng et al . 2007a,b).…”

“…2010). Some physiological functions of AOX have been proposed and its possible role in optimizing photosynthesis has attracted much attention recently (Raghavendra & Padmasree 2003; Yoshida, Terashima & Noguchi 2006, 2007; Feng et al . 2007a,b; Giraud et al .…”

Signal Pathways for Regulation of Plant Alternative Oxidase Genes’ Expression

“…However, opposite cases exist. Orthologous genes АОХ1а and АОХ1с of wheat and rice showed different patterns of expression in the course of leaf greening [44,45].…”

“…At present, light regulation of АОХ expression is being actively investigated [7,32,36,44,72]. AOX is considered to participate in oxidation of excess NADPH of a chloroplastic origin promoting the unloading of chlETC [73,74].…”

“…A signal from photoreceptors to the stage of АОХ transcription is transduced by means of known mechanisms of phototransduction of light-regulated (and first of all, photosynthetic) genes [76]. Light-dependent nature of АОХ1а induction was revealed in the leaves of A. thaliana [36,51,75] and Triticum aestivum [32], AOX2a in cotyledons of Glycine max [77], and АОХ1с in the leaves of Oryza sativa [44].…”