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EFFECTS OF METHYL VIOLOGEN IN LOW CONCENTRATIONS

ON GROWTH AND PHOTOSYNTHESIS IN MUTANTS OF

SYNECHOCOCCUS

SP. PCC 7942 AND

SYNECHOCYSTIS

SP. PCC

6803 THAT ARE DEFICIENT IN ANTIOXIDANT GENES

I.R. Fomina1, T.l. Balakhnina1, S.M. Hertz1, A.A. Ivanov1, E.P.

Ivanova1, A.A. Kosobrukhov1, V.D. Kreslavski1,

V.Yu.

Lyubimov1,

G.N. Nazarova1, O.P. Serdyuk1, S.M. Smoligina1, K.Y. Biel1,2, S.K.

Herbert3

'institute of Basic Biological Problems RAS, Pushchino, Moscow

Region, Russia, (0967)-732988,

fomi@mail.ru

; 2Center for the

Investigation of Food and Development, Hermosillo, Sonora, Mexico;

^Department of Botany, University of Wyoming, Laramie, WY, USA

Recently [1] we reported that the mutant of

Synechococcus

sp.

PCC 7942 lacking

sodB

gene [2] and the mutant of

Synechocystis

sp.

PCC 6803 lacking

katG

gene grew slower than their wild types at

higher light conditions (300 pmol photons m'2 s"1). The

sodE

mutant

of PCC 7942 displayed also smaller level of light-saturated 0 2

evolution. With photoinhibition treatment (60 s exposition at 1200

pmol photons m'2

s ]

in the presence of 80 pM chloramphenicol), none

of the mutant strains showed accelerated loss of light-limited 0 2

evolution relative to their wild types, but the

sodB'

mutant of PCC

7942 showed, however, a tendency to accelerated loss of light-

saturated 0 2 evolution [1]. The results suggested that none of the

genes

(sodB

and

katG

) protects photosystem II (PS II) from

photoinhibition damage under conditions of excessive light. The

sodB

mutant of PCC 7942 was proposed to be sensitized to oxidative damage

at a point downstream of PS I [2-5]. To improve understanding of

physiological roles of

sodB

and

katG

genes in phototrophic cells, the

effects of 0.5 pM methyl viologen (MV) on these mutant cultures were

examined. Cultures were grown in liquid BGI1 medium enriched by

10 mM NaHCCb under 30 pmol photons m'2 s'1, 28 °C and 3% C02

aeration. The in concentration 0.5 pM found to be a strong stressor

for the

sodB

mutant of PCC 7942 but had no significant negative effect

on growth and photosynthesis in the

katG

mutant of PCC 6803 or in

the wild type strains (PCC 7942 and PCC 6803). Exposure to 0.5 pM

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