Limits...
Investigations on the photoregulation of chloroplast movement and leaf positioning in Arabidopsis.

Han IS, Cho HY, Moni A, Lee AY, Briggs WR - Plant Cell Physiol. (2012)

Bottom Line: The effect is far-red reversible.This photoreversible response is normal in a phyB mutant but does not appear in a phyA mutant.These results suggest that phyA mediates the enhancement, induced by a red light pulse, of blue light-induced chloroplast movements.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, University of Ulsan, Ulsan 680-749, Korea. hanis@ulsan.ac.kr

ABSTRACT
We recently investigated the roles of the phototropin 1 (PHOT1) LOV (light, oxygen or voltage) domains in mediating phototropic curvature in transgenic Arabidopsis seedlings expressing either wild-type PHOT1 or PHOT1 with one or both LOV domains inactivated by a single amino acid replacement. We have now investigated the role of the PHOT1 LOV domains in chloroplast movement and in leaf positioning in response to blue light. Low fluence rate blue light is known to mediate a chloroplast accumulation response and high fluence rate blue light an avoidance response in Arabidopsis leaves. As was the case for phototropism, LOV2 of PHOT1 is essential for chloroplast accumulation and LOV1 is dispensable. PHOT1 LOV2 is also essential to maintain developing primary leaves in a horizontal position under white light from above and LOV1 is again dispensable. A red light pulse given to dark-adapted light-grown plants followed by 2 h of darkness enhances both the chloroplast accumulation response under dim blue light and the chloroplast avoidance response under strong blue light. The effect is far-red reversible. This photoreversible response is normal in a phyB mutant but does not appear in a phyA mutant. These results suggest that phyA mediates the enhancement, induced by a red light pulse, of blue light-induced chloroplast movements.

Show MeSH

Related in: MedlinePlus

Chloroplast movement phenotypes in wild-type (gl1), phot single mutants (phot1-5 and phot2-1), the untransformed double mutant (phot1-5 phot2-1) and representative double mutant phot1-5 phot2-1 seedlings transformed with PHOT expression constructs. Leaves were treated for 30 min at the indicated fluence rates of blue light. Images of the chloroplast movement; a comparison of the darkness of the illuminated strip with that of the covered areas was analyzed by Image J software. Error bars are the SEM. n = 12. The experiment was carried out three times with similar results.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3539441&req=5

pcs098-F1: Chloroplast movement phenotypes in wild-type (gl1), phot single mutants (phot1-5 and phot2-1), the untransformed double mutant (phot1-5 phot2-1) and representative double mutant phot1-5 phot2-1 seedlings transformed with PHOT expression constructs. Leaves were treated for 30 min at the indicated fluence rates of blue light. Images of the chloroplast movement; a comparison of the darkness of the illuminated strip with that of the covered areas was analyzed by Image J software. Error bars are the SEM. n = 12. The experiment was carried out three times with similar results.

Mentions: To investigate the function of the two phototropin LOV domains in PHOT1 and PHOT2 on chloroplast movement, we grew the transgenic lines transformed with the wild-type phototropin genes PHOT1 or PHOT2, or these genes with one or both of the two LOV domains inactivated. We measured chloroplast accumulation or avoidance in a central strip across Arabidopsis leaves on illumination with blue light of different fluence rates (Fig. 1). Blue light treatment of any of the four non-transformed lines (gl1, phot1-5/phot2-1, phot 1-5 or phot2-1) produced a response as predicted by the literature (Kagawa et al. 2001, Suetsugu and Wada 2003): whenever PHOT2 was present (gl1 and phot1-5), low fluence rates induced accumulation (above the 0.0 line in the figure) and high fluence rates induced avoidance (below the 0.0 line). The double mutant (phot1-5 phot2-1) was not entirely inactive, but showed a slight accumulation response, probably caused because the phot2-1 mutation is known to be leaky (Cho et al. 2007). With wild-type levels of PHOT1 present (the phot2-1 mutant), accumulation was the only response. The reduced chloroplast accumulation in this line at the highest fluence rate tested could have been caused by the small amount of PHOT2 produced by the leaky phot2-1 mutant which has a point mutation in the splice site juction, in antagonism to the PHOT1-mediated accumulation movement (see Discussion).Fig. 1


Investigations on the photoregulation of chloroplast movement and leaf positioning in Arabidopsis.

Han IS, Cho HY, Moni A, Lee AY, Briggs WR - Plant Cell Physiol. (2012)

Chloroplast movement phenotypes in wild-type (gl1), phot single mutants (phot1-5 and phot2-1), the untransformed double mutant (phot1-5 phot2-1) and representative double mutant phot1-5 phot2-1 seedlings transformed with PHOT expression constructs. Leaves were treated for 30 min at the indicated fluence rates of blue light. Images of the chloroplast movement; a comparison of the darkness of the illuminated strip with that of the covered areas was analyzed by Image J software. Error bars are the SEM. n = 12. The experiment was carried out three times with similar results.
© Copyright Policy - creative-commons
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3539441&req=5

pcs098-F1: Chloroplast movement phenotypes in wild-type (gl1), phot single mutants (phot1-5 and phot2-1), the untransformed double mutant (phot1-5 phot2-1) and representative double mutant phot1-5 phot2-1 seedlings transformed with PHOT expression constructs. Leaves were treated for 30 min at the indicated fluence rates of blue light. Images of the chloroplast movement; a comparison of the darkness of the illuminated strip with that of the covered areas was analyzed by Image J software. Error bars are the SEM. n = 12. The experiment was carried out three times with similar results.
Mentions: To investigate the function of the two phototropin LOV domains in PHOT1 and PHOT2 on chloroplast movement, we grew the transgenic lines transformed with the wild-type phototropin genes PHOT1 or PHOT2, or these genes with one or both of the two LOV domains inactivated. We measured chloroplast accumulation or avoidance in a central strip across Arabidopsis leaves on illumination with blue light of different fluence rates (Fig. 1). Blue light treatment of any of the four non-transformed lines (gl1, phot1-5/phot2-1, phot 1-5 or phot2-1) produced a response as predicted by the literature (Kagawa et al. 2001, Suetsugu and Wada 2003): whenever PHOT2 was present (gl1 and phot1-5), low fluence rates induced accumulation (above the 0.0 line in the figure) and high fluence rates induced avoidance (below the 0.0 line). The double mutant (phot1-5 phot2-1) was not entirely inactive, but showed a slight accumulation response, probably caused because the phot2-1 mutation is known to be leaky (Cho et al. 2007). With wild-type levels of PHOT1 present (the phot2-1 mutant), accumulation was the only response. The reduced chloroplast accumulation in this line at the highest fluence rate tested could have been caused by the small amount of PHOT2 produced by the leaky phot2-1 mutant which has a point mutation in the splice site juction, in antagonism to the PHOT1-mediated accumulation movement (see Discussion).Fig. 1

Bottom Line: The effect is far-red reversible.This photoreversible response is normal in a phyB mutant but does not appear in a phyA mutant.These results suggest that phyA mediates the enhancement, induced by a red light pulse, of blue light-induced chloroplast movements.

View Article: PubMed Central - PubMed

Affiliation: School of Biological Sciences, University of Ulsan, Ulsan 680-749, Korea. hanis@ulsan.ac.kr

ABSTRACT
We recently investigated the roles of the phototropin 1 (PHOT1) LOV (light, oxygen or voltage) domains in mediating phototropic curvature in transgenic Arabidopsis seedlings expressing either wild-type PHOT1 or PHOT1 with one or both LOV domains inactivated by a single amino acid replacement. We have now investigated the role of the PHOT1 LOV domains in chloroplast movement and in leaf positioning in response to blue light. Low fluence rate blue light is known to mediate a chloroplast accumulation response and high fluence rate blue light an avoidance response in Arabidopsis leaves. As was the case for phototropism, LOV2 of PHOT1 is essential for chloroplast accumulation and LOV1 is dispensable. PHOT1 LOV2 is also essential to maintain developing primary leaves in a horizontal position under white light from above and LOV1 is again dispensable. A red light pulse given to dark-adapted light-grown plants followed by 2 h of darkness enhances both the chloroplast accumulation response under dim blue light and the chloroplast avoidance response under strong blue light. The effect is far-red reversible. This photoreversible response is normal in a phyB mutant but does not appear in a phyA mutant. These results suggest that phyA mediates the enhancement, induced by a red light pulse, of blue light-induced chloroplast movements.

Show MeSH
Related in: MedlinePlus