Abstract
Plastid-nucleus-located WHIRLY1 protein plays a role in regulating leaf senescence and is believed to associate with the increase of reactive oxygen species delivered from redox state of the photosynthetic electron transport chain. In order to make sure whether WHIRLY1 plays a role in photosynthesis, in this study, the performances of photosynthesis were detected in Arabidopsis whirly1 knockout (kowhy1) and plastid localized WHIRLY1 overexpression (oepWHY1) plants. Loss of WHIRLY1 leads to a higher photochemical quantum yield of photosystem I Y(I) and electron transport rate (ETR) and a lower non-photochemical quenching (NPQ) involved in the thermal dissipation of excitation energy of chlorophyll fluorescence than the wild type. Further analyses showed that WHIRLY1 interacts with Light-harvesting protein complex I (LHCA1) and affects the expression of genes encoding photosystem I (PSI) and light harvest complexes (LHCI). Moreover, loss of WHIRLY1 decreases chloroplast NAD(P)H dehydrogenase-like complex (NDH) activity and the accumulation of NDH supercomplex. Several genes encoding the PSI-NDH complexes are also up-regulated in kowhy1 and the whirly1whirly3 double mutant (ko1/3) but steady in oepWHY1 plants. However, under high light conditions (800 μmol m−2 s−1), both kowhy1 and ko1/3 plants show lower ETR than wild-type which are contrary to that under normal light condition. Moreover, the expression of several PSI-NDH encoding genes and ERF109 which is related to jasmonate (JA) response varied in kowhy1 under different light conditions. These results indicate that WHIRLY1 is involved in the alteration of ETR by affecting the activities of PSI and supercomplex formation of PSI with LHCI or NDH and may acting as a communicator between the plastids and the nucleus.
Highlights
Chloroplasts serve as sensors of environmental conditions and guide plants toward proper adaption [1]
The function of the photosynthetic machinery can be probed by chlorophyll fluorescence emission by photosystem II (PSII) and light absorption by P700 reaction center chl a of photosystem I (PSI) [22]
To determine whether photosynthetic performance at leaf early senescence stage is affected by WHY1 in Arabidopsis, photosynthetic parameters in WHY1 mutants were measured
Summary
Chloroplasts serve as sensors of environmental conditions and guide plants toward proper adaption [1]. Photosynthetic light reactions are essential to the retrograde plastid-to-nucleus signaling which contributes to the coordination of chloroplast function by regulating nuclear gene expression [4,5,6]. The why1why3polIb-1 mutants showed lower photosynthetic electron transport efficiencies and higher accumulation of reactive oxygen species compared to wild-type plants [16]. The detail role of WHY1 in both pathways remains unknown Performances of photosynthesis such as optimization of electron transport, carbon assimilation, and assimilate production are important at all stages of leaf development, especially during senescence when chloroplasts are dismantled and photosynthetic proteins are recycled for vegetative or reproductive development and in particular for grain filling [20]. Our results suggest that WHY1 is involved in regulating the photosynthesis process during senescence and stress
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