Stimulation of chlororespiration by heat and high light intensity in oat plants

Abstract

High irradiance and moderate heat inhibit the activity of the photosynthetic apparatus of oat ( Avena sativa L.) leaves. The incubation of oat leaves under high light intensity in conjunction with high temperatures strongly decreased the maximal quantum yield of photosystem (PS) II, indicating the close synergistic effect of both stress factors on PS II inhibition and the subsequent irreversible damage to the photosynthetic apparatus. The PS I A/B protein levels remained similar to control values in leaves incubated under high light intensity or moderate heat, and decreased only when both stress factors were simultaneously applied. Immunoblot analysis of thylakoid membranes using specific antibodies raised against the NDH-K subunit of the thylakoidal NADH dehydrogenase complex (NADH DH) and against plastid terminal oxidase (PTOX) revealed an increase in the amount of both proteins in response to high light intensity and/or heat treatments. In addition, these stress treatments were seen to stimulate the activity of electron donation by NADPH and ferredoxin to plastoquinone, the PTOX activity in plastoquinone oxidation and the NADH DH activity in thylakoid membranes. Incubation with n -propyl gallate (an inhibitor of PTOX) inhibited the increase of NDH-K and PTOX levels under high light intensity and heat, and slightly stimulated the activity of electron donation by NADPH and ferredoxin to plastoquinone. Antimycin A (an inhibitor of cyclic electron flow) increased the NADH DH activity and preserved the levels of NDH-K and PTOX in thylakoid membranes from leaves incubated under high light intensity and heat. The up-regulation of the PTOX and the thylakoidal NADH DH complex under these stress conditions supports a role for chlororespiration in the protection against high irradiance and moderate heat.

An Arabidopsis Mutant with High Cyclic Electron Flow around Photosystem I (hcef) Involving the NADPH Dehydrogenase Complex

“…This conclusion is consistent with the reported strong correlation between the expression levels of NDH, but not PGR5, and the extent of CEF1 in C 4 plants (Takabayashi et al, 2005;Darie et al, 2006). Our results may also explain the apparent discrepancy between the apparent function of NDH, as a NAD(P) H:plastoquinone oxidoreductase, and its very low expression levels under permissive conditions (Sazanov et al, 1996;Quiles, 2005) where the need for CEF1 is minimal but strongly upregulated under stress where ATP demand may be high (Sazanov et al, 1998;Nixon, 2000;Quiles, 2006), requiring the activation of CEF1 or chlororespiration. Our results do not rule out the participation of PGR5 in CEF1 under other conditions, but because we observe high CEF1 and q E responses in hcef1 pgr5, this protein does not appear to be essential either for CEF1 or for induction of photoprotection (Munekage et al, 2002).…”

Dual Role of the Plastid Terminal Oxidase in Tomato

“…allowing the transfer of excess electrons to O 2 ) is essentially provided for higher plants by gene expression/protein accumulation data (Rizhsky et al, 2002;Baena-Gonzalez et al, 2003;Quiles, 2006). However, PTOX remains a minor constituent of photosynthetic membranes (Lennon et al, 2003) with the notable exception of alpine plants such as Geum montanum and R. glacialis (Streb et al, 2005), which may have selected natural overexpressers as an additional protection mechanism.…”

Effects of n-propyl gallate on photosynthesis and physiological parameters in Dunaliella salina are affected by stressful conditions

“…Under environmental stress conditions, such as salinity and high irradiance, plants show the ingenious adaptations at all levels of organization, from morphological to biochemical, molecular, and physiological levels (Diaz et al, 2007). At the biochemical and physiological levels, plants can alter their flow of photosynthetic electron transfer in several ways in order to cope with the stress (Dijkman and Kroon, 2002;Quiles, 2006;Diaz et al, 2007;Gamboa et al, 2009;Ibanez et al, 2010).…”

“…Plants have developed individual tolerance mechanisms to cope with the environmental stress during evolutional processes, as the mechanisms are much varied between species and different groups (Quiles, 2006;Diaz et al, 2007). Under environmental stress conditions, such as salinity and high irradiance, plants show the ingenious adaptations at all levels of organization, from morphological to biochemical, molecular, and physiological levels (Diaz et al, 2007).…”

“…Stress usually refers to an unfavorable condition in which an external factor exerts undesirable influence on plants, and it can cause the happening of special responses in all physiological levels of an organism (Quiles, 2006;Diaz et al, 2007;Ibanez et al, 2010). Plants have developed individual tolerance mechanisms to cope with the environmental stress during evolutional processes, as the mechanisms are much varied between species and different groups (Quiles, 2006;Diaz et al, 2007).…”