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Apo-bacteriophytochromes modulate bacterial photosynthesis in response to low light.

ABSTRACT: Bacteriophytochromes (BphPs) are light-sensing regulatory proteins encoded by photosynthetic and nonphotosynthetic bacteria. This protein class has been characterized structurally, but its biological activities remain relatively unexplored. Two BphPs in the anoxygenic photosynthetic bacterium Rhodopseudomonas palustris, designated regulatory proteins RpBphP2 and RpBphP3, are configured as light-regulated histidine kinases, which initiate a signal transduction system that controls expression of genes for the low light harvesting 4 (LH4) antenna complex. In vitro, RpBphP2 and RpBphP3 respond to light quality by reversible photoconversion, a property that requires the light-absorbing chromophore biliverdin. In vivo, RpBphP2 and RpBphP3 are both required for the expression of the LH4 antenna complex under anaerobic conditions, but biliverdin requires oxygen for its synthesis by heme oxygenase. On further investigation, we found that the apo-bacteriophytochrome forms of RpBphP2 and RpBphP3 are necessary and sufficient to control LH4 expression in response to light intensity in conjunction with other signal transduction proteins. One possibility is that the system senses a reduced quinone pool generated when light energy is absorbed by bacteriochlorophyll. The biliverdin-bound forms of the BphPs have the additional property of being able to fine-tune LH4 expression in response to light quality. These observations support the concept that some bacteriophytochromes can function with or without a chromophore and may be involved in regulating physiological processes not directly related to light sensing.

SUBMITTER: Fixen KR

PROVIDER: S-EPMC3896181 | biostudies-literature | 2014 Jan

REPOSITORIES: biostudies-literature

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Apo-bacteriophytochromes modulate bacterial photosynthesis in response to low light.

Fixen Kathryn R KR Baker Anna W AW Stojkovic Emina A EA Beatty J Thomas JT Harwood Caroline S CS

Proceedings of the National Academy of Sciences of the United States of America 20131230 2

Bacteriophytochromes (BphPs) are light-sensing regulatory proteins encoded by photosynthetic and nonphotosynthetic bacteria. This protein class has been characterized structurally, but its biological activities remain relatively unexplored. Two BphPs in the anoxygenic photosynthetic bacterium Rhodopseudomonas palustris, designated regulatory proteins RpBphP2 and RpBphP3, are configured as light-regulated histidine kinases, which initiate a signal transduction system that controls expression of g ...[more]

PMID: 24379368

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Project description:IntroductionLow light stress inhibits plant growth due to a line of physiological disruptions in plants, and is one of the major barriers to protected cucumber cultivation in northern China.MethodsTo comprehensively understand the responses of cucumber seedlings to low-light stress, the low-light-tolerant line (M67) and The low-light-sensitive line (M14) were conducted for the analysis of photosynthetic phenotype, RNA sequencing (RNA-seq) and the expression level of photosynthesis-related genes in leaves under low-light stress and normal light condition (control).ResultsThe results showed that there was a sharp decrease in the photosynthate accumulation in the leaves of the sensitive line, M14, resulting in a large decrease in the photosynthetic rate (Pn) (with 31.99%) of leaves compared to that of the control, which may have been caused by damage to chloroplast ultrastructure or a decrease in chlorophyll (Chl) content. However, under the same low-light treatment, there was no large drop in the photosynthate accumulation and even no decrease in Pn and Chl content for the tolerant line, M67. Moreover, results of gene expression analysis showed that the expression level of genes CsPsbQ (the photosystem II oxygen-evolving enhancer protein 3 gene) and Csgamma (ATPase, F1 complex gene) in the M14 leaves decreased sharply (by 35.04% and 30.58%, respectively) compared with the levels in the M67 leaves, which decreased by 14.78% and 23.61%, respectively. The expression levels of genes involved in Chl synthesis and carbohydrate biosynthesis in the leaves of M14 decreased markedly after low-light treatment; in contrast, there were no sharp decreases or changes in leaves of M67.DiscussionOver all, the ability of cucumber to respond to low-light stress, as determined on the basis of the degree of damage in leaf structure and chloroplast ultrastructure, which corresponded to decreased gene expression levels and ATP phosphorylase activity, significantly differed between different low-light-tolerant lines, which was manifested as significant differences in photosynthetic capacity between them. Results of this study will be a reference for comprehensive insight into the physiological mechanism involved in the low-light tolerance of cucumber.

Dataset Information

Apo-bacteriophytochromes modulate bacterial photosynthesis in response to low light.

Publications

Apo-bacteriophytochromes modulate bacterial photosynthesis in response to low light.

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