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Small One-Helix Proteins Are Essential for Photosynthesis in Arabidopsis.

ABSTRACT: The extended superfamily of chlorophyll a/b binding proteins comprises the Light-Harvesting Complex Proteins (LHCs), the Early Light-Induced Proteins (ELIPs) and the Photosystem II Subunit S (PSBS). The proteins of the ELIP family were proposed to function in photoprotection or assembly of thylakoid pigment-protein complexes and are further divided into subgroups with one to three transmembrane helices. Two small One-Helix Proteins (OHPs) are expressed constitutively in green plant tissues and their levels increase in response to light stress. In this study, we show that OHP1 and OHP2 are highly conserved in photosynthetic eukaryotes, but have probably evolved independently and have distinct functions in Arabidopsis. Mutations in OHP1 or OHP2 caused severe growth deficits, reduced pigmentation and disturbed thylakoid architecture. Surprisingly, the expression of OHP2 was severely reduced in ohp1 T-DNA insertion mutants and vice versa. In both ohp1 and ohp2 mutants, the levels of numerous photosystem components were strongly reduced and photosynthetic electron transport was almost undetectable. Accordingly, ohp1 and ohp2 mutants were dependent on external organic carbon sources for growth and did not produce seeds. Interestingly, the induction of ELIP1 expression and Cu/Zn superoxide dismutase activity in low light conditions indicated that ohp1 mutants constantly suffer from photo-oxidative stress. Based on these data, we propose that OHP1 and OHP2 play an essential role in the assembly or stabilization of photosynthetic pigment-protein complexes, especially photosystem reaction centers, in the thylakoid membrane.

SUBMITTER: Beck J

PROVIDER: S-EPMC5253381 | biostudies-literature | 2017

REPOSITORIES: biostudies-literature

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Small One-Helix Proteins Are Essential for Photosynthesis in Arabidopsis.

Beck Jochen J Lohscheider Jens N JN Albert Susanne S Andersson Ulrica U Mendgen Kurt W KW Rojas-Stütz Marc C MC Adamska Iwona I Funck Dietmar D

Frontiers in plant science 20170123

The extended superfamily of chlorophyll <i>a/b</i> binding proteins comprises the Light-Harvesting Complex Proteins (LHCs), the Early Light-Induced Proteins (ELIPs) and the Photosystem II Subunit S (PSBS). The proteins of the ELIP family were proposed to function in photoprotection or assembly of thylakoid pigment-protein complexes and are further divided into subgroups with one to three transmembrane helices. Two small One-Helix Proteins (OHPs) are expressed constitutively in green plant tissue ...[more]

PMID: 28167950

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Project description:Mitochondria play important roles in the plant stress responses and the detoxification of the reactive oxygen species generated in the electron transport chain. Expression of genes encoding stress-related proteins such as the mitochondrial small heat shock proteins (M-sHSP) is upregulated in response to different abiotic stresses. In Arabidopsis thaliana, three M-sHSPs paralogous genes were identified, although their function under physiological conditions remains elusive. The aim of this work is to uncover the in vivo function of all three M-sHSPs at the whole plant level. To accomplish this goal, we analyzed the phenotype, proteomic, and metabolic profiles of Arabidopsis knock-down lines of M-sHSPs (single, double, and triple knock-down lines) during normal plant growth. The triple knock-down plants showed the most prominent altered phenotype at vegetative and reproductive stages without any externally applied stress. They displayed chlorotic leaves, growth arrest, and low seed production. Concomitantly, they exhibited increased levels of sugars, proline, and citric, malic, and ascorbic acid, among other metabolites. In contrast, single and double knock-down plants displayed a few changes in their phenotype. A redundant function among the three M-sHSPs is indicated by the impairment in vegetative and reproductive growth associated with the simultaneous loss of all three M-sHSPs genes. The triple knock-down lines showed alteration of proteins mainly involved in photosynthesis and antioxidant defense compared to the control plants. On the other hand, heat stress triggered a distinct cytosolic response pattern and the upregulation of other sHSP members, in the knock-down plants. Overall, depletion of all three M-sHSPs in Arabidopsis severely impacted fundamental metabolic processes, leading to alterations in the correct plant growth and development. These findings expand our knowledge about the contribution of organelle-specific M-sHSPs to healthy plant growth under non-stress conditions.

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Small One-Helix Proteins Are Essential for Photosynthesis in Arabidopsis.

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Small One-Helix Proteins Are Essential for Photosynthesis in Arabidopsis.

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