Rannunculus Anglais - Station Alpine Joseph Fourier

Project Description
Joseph Fourier Alpine Station
Project Title: The role of the antioxidants ascorbate and glutathion in the stress resistance of
S. alpina and R. glacialis
Key Words: ascorbate, glutathion, photoinhibition, low temperatures, high temperatures
Project Leader: Peter STREB (peter.streb@u-psud.fr)
Principal Participants: Peter Streb (Plant ecophysiology laboratory, university Paris XI)
Collaborations: Richard Bligny (PCV laboratory)
Project Objectives and Context : The two alpine plants Soldanella alpina and Ranunculus
glacialis contain very different concentrations of antioxidants within their leaves. The
concentration of antioxidants and the activity of antioxidant enzymes are often correlated with
the resistance of acclimatised leaves to stress due to cold and intense light. In particular, the
concentration of ascorbate is exceptionally high in leaves of S. alpina, while it remains
relatively low in R. glacialis. Nevertheless, these two plants both tolerate stresses due to cold
temperatures and high light. Consequently tolerance to these stresses does not only depend on
the capacity of the antioxidant system. These results pose the question of what is the role of
antioxidants in resistance to cold and high light versus other forms of stress found at high
altitude.
Due to global climatic change temperatures are increasing in the alpine region. During 2003
on certain days maximum temperatures reached 40°C at 2300m. We have shown that such
temperatures, coupled with high light intensities, result in photoinhibition in S. alpina and R.
glacialis, with a stronger effect in leaves of R. glacialis than in those of S. alpina. This
observation poses the question of whether high concentrations of antioxidants play a more
important role in the protection of leaves under high temperatures than under low
temperatures. S. alpina retains its green leaves over winter and flowers in springtime while
still covered by snow. In contrast, R. glacialis survives over winter only as underground
organs. The high concentration of ascorbate in the leaves of S. alpina is likely due to the fact
that this plant continues photosynthetic activity over winter, under the snow pack, despite low
temperatures (melting snow) and very high light intensities.
Concentrations of ascorbate and glutathion (reduced AA, GSH and oxide DHAA,
GSSG) in leaves of S. alpina and R. glacialis, in mol per mg chlorophyll
Possible Roles of Ascorbate
• Increases tolerance to photoinhibition due to low or high temperatures?
• Linked to protein synthesis?
• Allows the survival of leaves over winter?
• Allows early flowering?

Approaches / Methods: Climatic parameters and concentrations of antioxidants are being
measured throughout the year. The objective is to determine the conditions which induce the
greatest accumulation of antioxidants in S. alpina and to observe the resulting effects on stress
resistance, leaf survival over winter and on flowering. The concentrations of ascorbate are
increased in the presence of the acid L-galactonic γ lactone, a precursor in the synthesis of
ascorbate. Concentrations of glutathion are decreased in the presence of DL buthionine
sulfoximine, an inhibitor of the synthesis of glutathion. Leaves containing varying
concentrations of anti oxidants are exposed to low and high temperatures coupled with high
light intensities to study the role of antioxidants in stress tolerance.
Expected Results: Modification of the foliar concentration of antioxidants in vivo allows
measurement of the role of anti oxidants in stress tolerance. In particular, a low concentration
of ascorbate and glutathion will show if these anti oxidants are necessary for the protection of
S. alpina against high light intensities, low temperatures or high temperatures. Similarly, it
will be possible to determine if ascorbate is necessary for the survival of leaves of S. alpina
under the snow pack over winter allowing photosynthesis and early flowering. A high (or
low) concentration of antioxidants in R. glacialis will show their role in protecting leaves
from the same stresses, and in particular to high temperatures. We hope to understand if a
high concentration of antioxidants favours resistance in the face of global climatic change and
if antioxidant protection systems can ameliorate the survival of plants in the case of
continuing increases in temperature in alpine regions.
Bibliography
Streb P, Feierabend J, Bligny R. (1997) Resistance to photoinhibition of photosystem II and
catalase and antioxidative protection in high mountain plants. Plant Cell Environ. 20:
1030-1040
Streb P, Shang W, Feierabend J, Bligny R. (1998) Divergent strategies of photoprotection in
high-mountain plants. Planta 207: 313-324
Streb P, Aubert S, Gout E, Bligny R (2003a) Reversibility of cold- and light-stress tolerance
and accompanying changes of metabolite and antioxidant levels in the two high mountain
plant species Soldanella alpina and Ranunculus glacialis. J. Exp. Bot. 54: 405-418
Streb P, Aubert S, Gout E, Bligny R. (2003b) Cold- and light-induced changes of metabolite
and antioxidant levels in two high mountain plant species Soldanella alpina and
Ranunculus glacialis and a lowland species Pisum sativum. Physiol. Plant. 118: 96-104
Streb P, Aubert S, Bligny R (2003c) High temperature effects on light sensitivity in the two
high mountain plant species Soldanella alpina (L) and Ranunculus glacialis (L). Plant
Biol. 5, 432-440
Streb P, Josse EM, Gallouët E, Baptist F, Kuntz M, Cornic G. (2005) Evidence for alternative
electron sinks to photosynthetic carbon assimilation in the high mountain plant species
Ranunculus glacialis. Plant, Cell Environment 28, 1123-1135