Abstract
Excised plant tissues (explants) can regenerate new shoot apical meristems in vitro, but regeneration rates can be inexplicably variable. Light affects rates of shoot regeneration, but the underlying mechanisms are poorly understood. Here, excised Arabidopsis cotyledons were dark-light shifted to define the timing of explant light sensitivity. Mutants and pharmacological agents were employed to uncover underlying physiological and genetic mechanisms. Unexpectedly, explants were most light sensitive during the initial hours post-excision with respect to shoot regeneration. Only ∼100 µmol m(-2 ) s(-1) of fluorescent light was sufficient to induce reactive oxygen species (ROS) accumulation in new explants. By 48 h post-excision, induction of ROS, or quenching of ROS by xanthophylls, increased or decreased shoot regeneration, respectively. Phytochrome A-mediated signalling suppressed light inhibition of regeneration. Early exposure to blue/UV-A wavelengths inhibited regeneration, involving photoreceptor CRY1. Downstream transcription factor HY5 mediated explant photoprotection, perhaps by promoting anthocyanin accumulation, a pigment also induced by cytokinin. Surprisingly, early light inhibition of shoot regeneration was dependent on polar auxin transport. Early exposure to ethylene stimulated dark-treated explants to regenerate, but inhibited light-treated explants. We propose that variability in long-term shoot regeneration may arise within the initial hours post-excision, from inadvertent, variable exposure of explants to light, modulated by hormones.
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Claims 14
Claim · model-written summary
Explants were most light sensitive during initial hours after excision.
Verbatim
e0“explants were most light sensitive during the initial hours post-excision with respect to shoot regeneration”
Claim · model-written summary
Fluorescent light of about 100 µmol induced ROS in new explants.
- Taxon
- explantse0
- Treatment
- ∼100 µmol m(-2 ) s(-1) of fluorescent lighte0
- Outcome
- reactive oxygen species (ROS) accumulatione0
Not reportedComparatorDirection
Verbatim
e0“Only ∼100 µmol m(-2 ) s(-1) of fluorescent light was sufficient to induce reactive oxygen species (ROS) accumulation in new explants”
Claim · model-written summary
ROS induction increased shoot regeneration by 48 hours.
- Taxon
- Arabidopsis cotyledonst0
- Treatment
- induction of ROSe0
- Outcome
- shoot regeneratione0
- Direction
- increasede0
Not reportedComparator
Verbatim
e0“By 48 h post-excision, induction of ROS, or quenching of ROS by xanthophylls, increased or decreased shoot regeneration, respectively”
t0“Arabidopsis cotyledons”
Claim · model-written summary
ROS quenching by xanthophylls decreased shoot regeneration.
- Taxon
- Arabidopsis cotyledonst0
- Treatment
- quenching of ROS by xanthophyllse0
- Outcome
- shoot regeneratione0
- Direction
- decreasede0
Not reportedComparator
Verbatim
e0“By 48 h post-excision, induction of ROS, or quenching of ROS by xanthophylls, increased or decreased shoot regeneration, respectively”
t0“Arabidopsis cotyledons”
Claim · model-written summary
Phytochrome A signaling suppressed light inhibition of regeneration.
Verbatim
e0“Phytochrome A-mediated signalling suppressed light inhibition of regeneration”
t0“Arabidopsis cotyledons”
Claim · model-written summary
Early blue/UV-A exposure inhibited regeneration.
- Taxon
- Arabidopsis cotyledonst0
- Treatment
- Early exposure to blue/UV-A wavelengthse0
- Gene
- CRY1e0
- Outcome
- regeneratione0
- Direction
- inhibitede0
Not reportedComparator
Verbatim
e0“Early exposure to blue/UV-A wavelengths inhibited regeneration, involving photoreceptor CRY1”
t0“Arabidopsis cotyledons”
Claim · model-written summary
CRY1 was involved in the blue/UV-A inhibition of regeneration.
Verbatim
e0“Early exposure to blue/UV-A wavelengths inhibited regeneration, involving photoreceptor CRY1”
t0“Arabidopsis cotyledons”
Claim · model-written summary
HY5 mediated explant photoprotection.
Verbatim
e0“Downstream transcription factor HY5 mediated explant photoprotection”
t0“Arabidopsis cotyledons”
Claim · model-written summary
HY5 perhaps promoted anthocyanin accumulation.
Verbatim
e0“perhaps by promoting anthocyanin accumulation”
t0“Arabidopsis cotyledons”
Claim · model-written summary
Cytokinin induced anthocyanin pigment.
Not reportedComparatorDirection
Verbatim
e0“a pigment also induced by cytokinin”
t0“Arabidopsis cotyledons”
Claim · model-written summary
Early light inhibition depended on polar auxin transport.
Verbatim
e0“early light inhibition of shoot regeneration was dependent on polar auxin transport”
t0“Arabidopsis cotyledons”
Claim · model-written summary
Ethylene stimulated regeneration in dark-treated explants.
Not reportedComparator
Verbatim
e0“Early exposure to ethylene stimulated dark-treated explants to regenerate”
Claim · model-written summary
Ethylene inhibited regeneration in light-treated explants.
Not reportedTreatmentComparator
Verbatim
e0“but inhibited light-treated explants”
t0“Arabidopsis cotyledons”
Claim · model-written summary
Authors proposed that early variable light exposure causes long-term regeneration variability.
Verbatim
e0“variability in long-term shoot regeneration may arise within the initial hours post-excision, from inadvertent, variable exposure of explants to light, modulated by hormones”
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