Investigation of the chlorophyll synthesis in plastid membranes:

The initial enzyme to start the synthesis of chlorophyll in light is NADPH-protochlorophyllide oxidoreductase (EC 1.3.1.33, POR). The group has studied the aggregation state of the POR, its localization in the lipid phase of the membranes and the enzyme conformational changes after irradiation, by energy transfer from tryptophan residues of membrane proteins to the fluorescence probes 1-aniline-8-naphthalene sulfonate (ANS) and pyrene. The membranes investigated were those accumulated in dark-grown wheat leaves - prolamellar bodies (PLBs) and prothylakoids (PTs). Changes in protein – probe interactions of the PLBs after irradiation has shown that POR is localized close to the membrane surface, most probably on the level of lipid polar heads. This supports the idea that the enzyme is not an integral membrane protein and is most probably localized on the membrane surface.

Photodynamic effect of pigment precursor in plants:

Some early precursors of chlorophyll biosynthesis such as δ-aminolevulinic acid (ALA) and glutamic acid (GA), together with the modulator of chlorophyll synthesis – 2,2´-dipyridyl (DP) have a photodynamic action on leaves. The accumulation of porphyrines, caused by the combination of chlorophyll precursor and DP, has a photodestructive effect on dicotylednous plants. The mechanism of this action is studied and it is believed that the one of the main reasons is the destruction of the cell membranes, which causes increased water transfer trough the membrane.

Connection between the carotenoid and chlorophyll synthesis:

The group has investigated the screening mechanism of carrotenoids on chlorophyll precursors synthesis. The herbicide norflurazon ( SAN) has been used to inhibit the caretonoid accumulation. Some ideas about membrane accumulation of the carrotenoid synthesis are expressed.

Recent Projects:

Photodynamic herbicides - NSF - Bulgaria

Enzymes of chlorophyll synthesis - NSF - Bulgaria

Carotenoids in photosynthetic membranes - NSF - Bulgaria

Recent Publications:

Denev I., Jahoubjan G., Minkov I., Sundqvist C., Light-induced changes of protochlorophyllide oxidoreductase organization in prolamellar bodies, isolated from etiolated carotenoid-deficient wheat plants, revealed by fluorescence probes, BBA. Biomembranes. 1716 (2): 97-103, 2005.

Denev, I., Yahubyan, G., Minkov, I. Recent advances in chloroplast development in higher plants. Handbook of Photosynthesis. Second Edition. M. Pessarakli, (Ed.), Taylor&Francis CRC Press, Inc., New York, 451-479, 2005.

Gechev, T. I. Gadjev, F. Van Breusegem, D. Inzé, S. Dukiandjiev, V. Toneva, I. Minkov. Hydrogen peroxide protects tobacco from oxidative stress by inducing a set of antioxidant enzymes. (CMLS), Cell. Mol. Life Sci. 59: 708-714. 2002.

Toneva V., N. Shalygo, E. Yaronskaya, N. Averina, I. Minkov. Influence of photodynamic processes induced by 2,2'-dipyridyl on the enzymatic system of chlorophyll biosynthesis. Photosynthetica, 34, 4, 555-560, 1997.

Toneva, V., Koleva, A., Minkov, I. Influence of glutamic acid and 2',2'-dipyridyl on the protochlorophyllide and protoporphyrine-IX accumulation and their photodynamic action in green monocotyledons and dicotyledons. J. Plant. Physiol., 150, 57-62, 1997.

Toneva, V., N.V. Shalygo, V.V. Voronetskaya, N, G. Averina, T. Gechev, I. Minkov. Investigation of the porphyrinogenesis in barley leaves incubated with Mn2+ cations and d-aminolevulinic aci. J. Plant Physiology, 159, 1047-1053, 2002.

Toneva, V., T. Gechev, I. Minkov. Induction of porphyrine biosynthesis by d-aminolevulinic acid, glutamic acid and 1,10-phenantroline and their possible photodynamic action in wheat and mustard plants. Photosynthetica, 39 (4): 597–601, 2001.

Yahubyan, G. I. Minkov, C. Sundqvist. Carotenoid dependence of protochlorophyllide phototransformation in dark-grown wheat seedlings. Photochem. Photobiol., 65, 171-176, 2001.

Staff involved:

Name Position Main research interest
Dr. Valentina TonevaResearch group leaderPhotodynamic herbicides, Plant Stress
Dr. Ilia DenevAssistant ProfessorChlorophyll synthesis, Chloroplast membranes
Prof. Ivan MinkovResearcher, ProfessorPigment-protein complexes, Chlorophyll synth.
Dr. Galina YahoubianAssistant ProfessorCarotenoid synthesis, Chlorophyll synthesis
Elisa NeshevaTechnician