Affiliation:
1. Dipartimento di Biotecnologie, Università di Verona, Verona 37134, Italy
2. Department of Biology, Kyushu University, Hakozaki 6-10-1, Fukuoka 812-8581, Japan
Abstract
Over-excitation of photosynthetic apparatus causing photoinhibition is counteracted by non-photochemical quenching (NPQ) of chlorophyll fluorescence, dissipating excess absorbed energy into heat. The PsbS protein plays a key role in this process, thus making the PsbS-less
npq4
mutant unable to carry out qE, the major and most rapid component of NPQ. It was proposed that
npq4
does perform qE-type quenching, although at lower rate than WT
Arabidopsis
. Here, we investigated the kinetics of NPQ in PsbS-depleted mutants of
Arabidopsis
. We show that red light was less effective than white light in decreasing maximal fluorescence in
npq4
mutants. Also, the kinetics of fluorescence dark recovery included a decay component, qM, exhibiting the same amplitude and half-life in both WT and
npq4
mutants. This component was uncoupler-sensitive and unaffected by photosystem II repair or mitochondrial ATP synthesis inhibitors. Targeted reverse genetic analysis showed that traits affecting composition of the photosynthetic apparatus, carotenoid biosynthesis and state transitions did not affect qM. This was depleted in the
npq4phot2
mutant which is impaired in chloroplast photorelocation, implying that fluorescence decay, previously described as a quenching component in
npq4
is, in fact, the result of decreased photon absorption caused by chloroplast relocation rather than a change in the activity of quenching reactions.
Subject
General Agricultural and Biological Sciences,General Biochemistry, Genetics and Molecular Biology
Cited by
49 articles.
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