Physiological Characterization of Phototropism in Arabidopsis Seedlings

Haga, Ken; Kimura, Taro

doi:10.1007/978-1-4939-9015-3_1

Cited by 5 publications

(5 citation statements)

References 25 publications

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“…For physiological experiments, etiolated Arabidopsis seedlings were prepared as described previously (Haga and Kimura, 2019). Briefly, Arabidopsis seeds were sown in 0.2-mL plastic tubes filled with 1.5% agar medium, placed in a black plastic box, and kept at 4°C for 3 to 5 days.…”

Section: Plant Materials and Growth Conditionsmentioning

confidence: 99%

“…During the experiments, seedlings were kept in a black plastic box under high humidity until needed. For immunoblotting and microscopy analyses, the etiolated seedlings were grown along the surface of vertically oriented agar medium (Haga and Kimura, 2019). Experimental manipulations were performed under dim green light.…”

Section: Plant Materials and Growth Conditionsmentioning

confidence: 99%

“…Phototropic stimulation was performed as described previously (Haga and Kimura, 2019). The phototropic curvatures of the hypocotyls were measured using CANVAS11 software (ACD Systems International Inc.).…”

Section: Induction Of Phototropism and Measurement Of The Curvaturementioning

confidence: 99%

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Phosphorylation of NONPHOTOTROPIC HYPOCOTYL3 affects photosensory adaptation during the phototropic response

et al. 2021

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Photosensory adaptation, which can be classified as sensor or effector adaptation, optimizes the light sensing of living organisms by tuning their sensitivity to changing light conditions. During the phototropic response in Arabidopsis (Arabidopsis thaliana), the light-dependent expression controls of blue-light photoreceptor phototropin 1 (phot1) and its modulator ROOT PHOTOTROPISM2 (RPT2) are known as the molecular mechanisms underlying sensor adaptation. However, little is known about effector adaption in plant phototropism. Here we show that control of the phosphorylation status of NONPHOTOTROPIC HYPOCOTYL3 (NPH3) leads to effector adaptation in hypocotyl phototropism. We generated unphosphorable and phosphomimetic NPH3 proteins on seven phosphorylation sites in the etiolated seedlings of Arabidopsis. Unphosphorable NPH3 showed a shortening of its retention time in the cytosol and caused an inability to adapt to very low fluence rates of blue light (∼10−5 µmol m−2 s−1) during the phototropic response. In contrast, the phosphomimetic NPH3 proteins had a lengthened retention time in the cytosol and could not enable the adaptation to blue light at fluence rates of 10−3 µmol m−2 s−1 or more. Our results indicate that the activation level of phot1 and the corresponding phosphorylation level of NPH3 determine the dissociation rate and the reassociation rate of NPH3 on the plasma membrane, respectively. These mechanisms may moderately maintain the active state of phot1 signaling across a broad range of blue-light intensities and contribute to the photosensory adaptation of phot1 signaling during the phototropic response in hypocotyls.

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Section: Plant Materials and Growth Conditionsmentioning

confidence: 99%

Section: Plant Materials and Growth Conditionsmentioning

confidence: 99%

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Phosphorylation of NONPHOTOTROPIC HYPOCOTYL3 affects photosensory adaptation during the phototropic response

et al. 2021

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“…Phototropic curvatures of hypocotyls were measured on agar medium in 0.2 ml tubes using the "advanced method" described previously (Haga et al 2012;Haga and Kimura, 2019).…”

Section: Measurement Of Phototropic Curvaturementioning

confidence: 99%

Arabidopsis ROOT PHOTOTROPISM2 Is a Light-Dependent Dynamic Modulator of Phototropin1

et al. 2020

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Arabidopsis thaliana phototropin1 (phot1) is a blue-light photoreceptor, i.e. a blue-light-activated Ser/Thr-protein kinase that mediates various light responses including phototropism. Phot1 functions in hypocotyl phototropism dependent on the light induction of ROOT PHOTOTROPISM2 (RPT2) proteins within a broad range of blue light intensities. It is not yet known however how RPT2 contributes to the photosensory adaptation of phot1 to high intensity blue light and the second positive phototropism. We here show that RPT2 suppresses the activity of phot1. Yeast two-hybrid analysis indicated RPT2 binding to the LOV1 (light, oxygen or voltage sensing 1) domain of phot1 required for its high photosensitivity. Our biochemical analyses revealed that RPT2 inhibits the autophosphorylation of phot1, suggesting that it suppresses the photosensitivity and/or kinase activity of phot1 through the inhibition of LOV1 function. We found for the first time that RPT2 proteins are degraded via a ubiquitin-proteasome pathway when phot1 is inactive and stabilized under blue-light conditions in a phot1-dependent manner. We propose that RPT2 is a molecular rheostat that maintains a moderate activation level of phot1 under any light intensity conditions.

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“…However, Gagliano et al, 2016 does not emphasize how surprising it is that plants would always grow towards a one hour presentation of light preceded by presentations in the opposite direction. Most experiments with phototropism involve light exposure from only one side and for substantially longer periods of time (3 hr in Schumacher et al, 2018 and Haga and Kimura, 2019 3–6 hr in Sullivan et al, 2016 or 24 hr in Goyal et al, 2016 ). Relatively few experiments have been reported on phototropism in etiolated Pisum sativum seedlings.…”

Section: Introductionmentioning

confidence: 99%

Response to comment on 'Lack of evidence for associative learning in pea plants'

Markel

2020

eLife

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In 2016 Gagliano et al. reported evidence for associative learning in plants (Gagliano et al., 2016). A subsequent attempt to replicate this finding by the present author was not successful (Markel, 2020). Gagliano et al. attribute this lack of replication to differences in the experimental set-ups used in the original work and the replication attempt (Gagliano et al., 2020). Here, based on a comparison of the two set-ups, I argue that these differences are unable to explain the lack of replication in Markel, 2020.

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Physiological Characterization of Phototropism in Arabidopsis Seedlings

Cited by 5 publications

References 25 publications

Phosphorylation of NONPHOTOTROPIC HYPOCOTYL3 affects photosensory adaptation during the phototropic response

Phosphorylation of NONPHOTOTROPIC HYPOCOTYL3 affects photosensory adaptation during the phototropic response

Arabidopsis ROOT PHOTOTROPISM2 Is a Light-Dependent Dynamic Modulator of Phototropin1

Response to comment on 'Lack of evidence for associative learning in pea plants'

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