Abstract
Phototropins (phots) are plasma membrane-associated serine/threonine kinases that coordinate a range of processes linked to optimizing photosynthetic efficiency in plants. These photoreceptors contain two light-, oxygen-, or voltage-sensing (LOV) domains within their N terminus, with each binding one molecule of flavin mononucleotide as a UV/blue lightabsorbing chromophore. Although phots contain two LOV domains, light-induced activation of the C-terminal kinase domain and subsequent receptor autophosphorylation is controlled primarily by the A-LOV2-J photosensory module. Mutations that disrupt interactions between the LOV2 core and its flanking helical segments can uncouple this mode of light regulation. However, the impact of these mutations on phot function in Arabidopsis has not been explored. Here we report that histidine substitution of Arg-472 located within the Ahelix of Arabidopsis phot1 constitutively activates phot1 kinase activity in vitro without affecting LOV2 photochemistry. Expression analysis of phot1 R472H in the phot-deficient mutant confirmed that it is autophosphorylated in darkness in vivo but unable to initiate phot1 signaling in the absence of light. Instead, we found that phot1 R472H is poorly functional under low-light conditions but can restore phototropism, chloroplast accumulation, stomatal opening, and leaf positioning and expansion at higher light intensities. Our findings suggest that Arabidopsis can adapt to the elevated phosphorylation status of the phot1 R472H mutant in part by reducing its stability, whereas the activity of the mutant under high-light conditions can be attributed to additional increases in LOV2-mediated photoreceptor autophosphorylation.
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Claims 7
Claim · model-written summary
The histidine substitution of Arg-472 constitutively activates phot1 kinase activity in vitro without affecting LOV2 photochemistry.
- Taxon
- Arabidopsis
Arabidopsise1 - Material
- histidine substitution of Arg-472e1
- Outcome
- phot1 kinase activitye1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“histidine substitution of Arg-472 located within the Ahelix of Arabidopsis phot1 constitutively activates phot1 kinase activity in vitro without affecting LOV2 photochemistry”
Claim · model-written summary
phot1 R472H is autophosphorylated in darkness in vivo but cannot initiate phot1 signaling without light.
- Taxon
- ArabidopsisArabidopsist0
- Material
- phot1 R472He2
- Outcome
- phot1 signalinge2
- Qualifier
- in the absence of lighte2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Arabidopsis phototropin 1”
e2“Expression analysis of phot1 R472H in the phot-deficient mutant confirmed that it is autophosphorylated in darkness in vivo but unable to initiate phot1 signaling in the absence of light”
Claim · model-written summary
phot1 R472H is poorly functional under low-light conditions.
- Taxon
- ArabidopsisArabidopsist0
- Material
- phot1 R472He3
- Treatment
- low-light conditionse3
- Outcome
- poorly functionale3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Arabidopsis phototropin 1”
e3“phot1 R472H is poorly functional under low-light conditions”
Claim · model-written summary
At higher light intensities phot1 R472H restores phototropism, chloroplast accumulation and stomatal opening.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- higher light intensitiese4
- Outcome
- phototropism, chloroplast accumulation, stomatal openinge4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Arabidopsis phototropin 1”
e4“can restore phototropism, chloroplast accumulation, stomatal opening, and leaf positioning and expansion at higher light intensities”
Claim · model-written summary
At higher light intensities phot1 R472H restores leaf positioning and expansion.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- higher light intensitiese4
- Outcome
- leaf positioning and expansione4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Arabidopsis phototropin 1”
e4“can restore phototropism, chloroplast accumulation, stomatal opening, and leaf positioning and expansion at higher light intensities”
Claim · model-written summary
Arabidopsis appears to adapt to the elevated phosphorylation of phot1 R472H in part by reducing its stability.
- Taxon
- ArabidopsisArabidopsise5
- Outcome
- reducing its stabilitye5
- Qualifier
- elevated phosphorylation status of the phot1 R472H mutante5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e5“Our findings suggest that Arabidopsis can adapt to the elevated phosphorylation status of the phot1 R472H mutant in part by reducing its stability”
Claim · model-written summary
High-light activity of the mutant may be attributed to additional increases in LOV2-mediated photoreceptor autophosphorylation.
- Taxon
- ArabidopsisArabidopsist0
- Outcome
- activity of the mutant under high-light conditionse6
- Qualifier
- additional increases in LOV2-mediated photoreceptor autophosphorylatione6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Arabidopsis phototropin 1”
e6“whereas the activity of the mutant under high-light conditions can be attributed to additional increases in LOV2-mediated photoreceptor autophosphorylation”