Dataset Information

Response of Chloroplast NAD(P)H Dehydrogenase-Mediated Cyclic Electron Flow to a Shortage or Lack in Ferredoxin-Quinone Oxidoreductase-Dependent Pathway in Rice Following Short-Term Heat Stress.

ABSTRACT: Cyclic electron flow (CEF) around photosystem I (PSI) can protect photosynthetic electron carriers under conditions of stromal over-reduction. The goal of the research reported in this paper was to investigate the responses of both PSI and photosystem II (PSII) to a short-term heat stress in two rice lines with different capacities of cyclic electron transfer, i.e., Q4149 with a high capacity (hcef) and C4023 with a low capacity (lcef). The absorbance change at 820 nm (ΔA820) was used here to assess the charge separation in the PSI reaction center (P700). The results obtained show that short-term heat stress abolishes the ferredoxin-quinone oxidoreductase (FQR)-dependent CEF in rice and accelerates the initial rate of P700 (+) re-reduction. The P700 (+) amplitude was slightly increased at a moderate heat-stress (35°C) because of a partial restriction of FQR but it was decreased following high heat-stress (42°C). Assessment of PSI and PSII activities shows that PSI is more susceptible to heat stress than PSII. Under high temperature, FQR-dependent CEF was completely removed and NDH-dependent CEF was up-regulated and strengthened to a higher extent in C4023 than in Q4149. Specifically, under normal growth temperature, hcef (Q4149) was characterized by higher FQR- and chloroplast NAD(P)H dehydrogenase (NDH)-dependent CEF rates than lcef (C4023). Following thermal stress, the activation of NDH-pathway was 130 and 10% for C4023 and Q4149, respectively. Thus, the NDH-dependent CEF may constitute the second layer of plant protection and defense against heat stress after the main route, i.e., FQR-dependent CEF, reaches its capacity. We discuss the possibility that under high heat stress, the NDH pathway serves as a safety valve to dissipate excess energy by cyclic photophosphorylation and overcome the stroma over-reduction following inhibition of CO2 assimilation and any shortage or lack in the FQR pathway. The potential role of the NDH-dependent pathway during the evolution of C4 photosynthesis is briefly discussed.

SUBMITTER: Essemine J

PROVIDER: S-EPMC4811871 | biostudies-literature | 2016

REPOSITORIES: biostudies-literature

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Publications

Response of Chloroplast NAD(P)H Dehydrogenase-Mediated Cyclic Electron Flow to a Shortage or Lack in Ferredoxin-Quinone Oxidoreductase-Dependent Pathway in Rice Following Short-Term Heat Stress.

Essemine Jemaa J Qu Mingnan M Mi Hualing H Zhu Xin-Guang XG

Frontiers in plant science 20160330

Cyclic electron flow (CEF) around photosystem I (PSI) can protect photosynthetic electron carriers under conditions of stromal over-reduction. The goal of the research reported in this paper was to investigate the responses of both PSI and photosystem II (PSII) to a short-term heat stress in two rice lines with different capacities of cyclic electron transfer, i.e., Q4149 with a high capacity (hcef) and C4023 with a low capacity (lcef). The absorbance change at 820 nm (ΔA820) was used here to as ...[more]

PMID: 27066033

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Project description:NAD(P)H:quinone oxidoreductase type I (NQO1) is a target enzyme for triggered delivery of drugs at inflamed tissue and tumor sites, particularly those that challenge traditional therapies. Prodrugs, macromolecules, and molecular assemblies possessing trigger groups that can be cleaved by environmental stimuli are vehicles with the potential to yield active drug only at prescribed sites. Furthermore, quinone propionic acids (QPAs) covalently attached to prodrugs or liposome surfaces can be removed by application of a reductive trigger stimulus, such as that from NQO1; their rates of reductive activation should be tunable via QPA structure. We explored in detail the recombinant human NAD(P)H:quinone oxidoreductase type I (rhNQO1)-catalyzed NADH reduction of a family of substituted QPAs and obtained high precision kinetic parameters. It is found that small changes in QPA structure-in particular, single atom and function group substitutions on the quinone ring at R(1)-lead to significant impacts on the Michaelis constant (K(m)), maximum velocity (V(max)), catalytic constant (k(cat)), and catalytic efficiency (k(cat)/K(m)). Molecular docking simulations demonstrate that alterations in QPA structure result in large changes in QPA alignment and placement with respect to the flavin isoalloxazine ring in the active site of rhNQO1; a qualitative relationship exists between the kinetic parameters and the depth of QPA penetration into the rhNQO1 active site. From a quantitative perspective, a very good correlation is observed between log(k(cat)/K(m)) and the molecular-docking-derived distance between the flavin hydride donor site and quinone hydride acceptor site in the QPAs, an observation that is in agreement with developing theories. The comprehensive kinetic and molecular modeling knowledge obtained for the interaction of recombinant human NQO1 with the quinone propionic acid analogues provides insight into the design and implementation of the QPA trigger groups for drug delivery applications.

Dataset Information

Response of Chloroplast NAD(P)H Dehydrogenase-Mediated Cyclic Electron Flow to a Shortage or Lack in Ferredoxin-Quinone Oxidoreductase-Dependent Pathway in Rice Following Short-Term Heat Stress.

Publications

Response of Chloroplast NAD(P)H Dehydrogenase-Mediated Cyclic Electron Flow to a Shortage or Lack in Ferredoxin-Quinone Oxidoreductase-Dependent Pathway in Rice Following Short-Term Heat Stress.

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