Delayed Fluorescence Measurements Show Increased S(2)Q(B)(-) Charge Recombination in PS2 of Tobacco Pigment-Deficient Aurea Mutant

Stefanov, Detelin and Milanov, Georgi and Lambrev, Petar and Kurteva, Maya and Abumhadi, Nabil (2018) Delayed Fluorescence Measurements Show Increased S(2)Q(B)(-) Charge Recombination in PS2 of Tobacco Pigment-Deficient Aurea Mutant. COMPTES RENDUS DE L ACADEMIE BULGARE DES SCIENCES, 71 (8). pp. 1052-1061. ISSN 1310-1331

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Abstract

Genetic transformation of plants often results in changed pigment content. Variation in pigment content directly induces changes in photosynthetic electron transport reactions. Fully expanded and deficient in chlorophylls tobacco leaves of aurea mutant, A1146, that expresses enhanced level of Q(B)-nonreducing PS2 centres and increased possibility for charge recombination of separated states in PS2 reaction centres were investigated. Long-term delayed fluorescence, DF, measured in second-to-minute time domains and temperature curve of delayed fluorescence, DFTC, was used to study slow PS2 charge recombination (S(2)Q(A)(-) and S(2)Q(B)(-)) in both wild type (line N1146) and a mutant A1146 tobacco plants. In conditions when S(2)Q(B)(-) recombination prevails in PS2 reaction centres, it causes increased possibility for PS2 photodamages. We found that despite of higher possibility for S(2)Q(B)(-) recombination in A1146 as evaluated by DF decay kinetics these plants do not differ from WT in their efficiency for photoprotection. The lack of B-like-band' in DFTC of leaves of both studied tobacco lines pre-illuminated for 6 min with low light intensities of 45 mu mol m(-2)s(-1) PPFD (LL) was observed. It was considered a manifestation of photoprotection at LL conditions through limiting possibility for S(2)Q(B)(-)-recombination. In leaves pre-illuminated for 6 min with high light intensities of 1200 mu mol m-(2)s(-1) PPFD (HL) A1146 half-drop of well-expressed B-band was shifted to higher temperatures. A possible photoprotection based on accumulation of Q(B)-nonreducing centres was discussed in details.

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