Abstract
The unicellular green alga Haematococcus pluvialis accumulates large amounts of the red ketocarotenoid astaxanthin to protect against environmental stresses. Haematococcus cells that accumulate astaxanthin in the central part (green-red cyst cells) respond rapidly to intense light by distributing astaxanthin diffusively to the peripheral part of the cell within 10 min after irradiation. This response is reversible: when astaxanthin-diffused cells were placed in the dark, astaxanthin was redistributed to the center of the cell. Although Haematococcus possesses several pigments other that astaxanthin, the subcellular distribution and content of each pigment remain unknown. Here, we analyzed the subcellular dynamics and localization of major pigments such as astaxanthin, β-carotene, lutein, and chlorophylls under light irradiation using time-lapse and label-free hyperspectral imaging analysis. Fluorescence microscopy and freeze-fracture transmission electron microscopy showed that, preceding/following exposure to light, astaxanthin colocalized with lipid droplets, which moved from the center to the periphery through pathways in a chloroplast. This study revealed that photoresponse dynamics differed between astaxanthin and other pigments (chlorophylls, lutein, and β-carotene), and that only astaxanthin freely migrates from the center to the periphery of the cell through a large, spherical, cytoplasm-encapsulating chloroplast as a lipid droplet. We consider this to be the Haematococcus light-protection mechanism.
Highlights
Land plants and algae have evolved strategies for adapting to changes in environmental conditions, such as sunlight intensity
We applied time-lapse live-imaging and hyperspectral imaging to quantitatively analyze the intracellular diffusion of carotenoids
We focused on lutein and β-carotene, as well as on astaxanthin and chlorophylls. β-Carotene is a major carotenoid as the precursor of astaxanthin
Summary
Land plants and algae have evolved strategies for adapting to changes in environmental conditions, such as sunlight intensity. The unicellular green alga Haematococcus pluvialis accumulates large amounts of the red ketocarotenoid astaxanthin, which plays an important role in protecting plants and algae from environmental stressors[7,8,9,10,11]. Under stress, such as intense light, Haematococcus cells increase the synthesis and accumulation of astaxanthin[12,13]. Nogami et al demonstrated the intracellular distribution of carotenoids and chlorophylls in Haematococcus at various life-cycle stages using hyperspectral imaging combined with the image-processing software HaematoCalMorph[31,32]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
