STRUCTURAL-FUNCTIONAL ORGANIZATION OF CHLOROPLASTS IN LEAVES OF XANTHA-702 MUTANT OF
GOSSYPIUM HIRSUTUM L.
V. G. Ladygin,1 G. A. Semenova,2 I. D. Shegay 1
1 Institute of Basic Biological Problems RAS, and 2 Institute of Theoretical and
Experimental Biophysics RAS, Pushchino, Moscow region;
e-mail: ladyginv@rambler.ru
For cotton mutant xantha (Gossypium hirsutum L.), it has been established that synthesis of
5-aminolevulinic acid was blocked in the light. In the light this mutant accumulates chlorophyll by 30 times lower as
compared to the parent type. In mutant xantha, a very few pigment-protein complexes of PS-I and PS-II are
formed in chloroplasts, and formation of membrane system in these is blocked at the early stages, in most cases, at
the stage of bubbles and single short thylakoids. Functional activity of reaction centers of PS-I and PS-II is close
to zero. Only light-harvesting chlorophyll-a/b protein complexes of the two photosystems are formed in mutant
xantha plastid membranes with maximum chlorophyll fluorescence at 728 and 681 nm, respectively. It has been
concluded that in mutant xantha genetic block of 5-aminolevulinic acid biosynthesis in the light disturbs the
formation and functioning of the complexes of reaction centers of PS-I and PS-II, hindering the development of the
whole membrane system in chloroplasts, causing a sharp decrease in productivity.
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