Blue light is essential for high light acclimation and photoprotection in the diatom Phaeodactylum tricornutum

Abstract

The objective of the present study was to test the hypothesis that the acclimation to different light intensities in the diatom Phaeodactylum tricornutum is controlled by light quality perception mechanisms. Therefore, semi-continuous cultures of P. tricornutum were illuminated with equal amounts of photosynthetically absorbed radiation of blue (BL), white (WL), and red light (RL) and in combination of two intensities of irradiance, low (LL) and medium light (ML). Under LL conditions, growth rates and photosynthesis rates were similar for all cultures. However, BL cultures were found to be in an acclimation state with an increased photoprotective potential. This was deduced from an increased capacity of non-photochemical quenching, a larger pool of xanthophyll cycle pigments, and a higher de-epoxidation state of xanthophyll cycle pigments compared to WL and RL cultures. Furthermore, in the chloroplast membrane proteome of BL cells, an upregulation of proteins involved in photoprotection, e.g. the Lhcx1 protein and zeaxanthin epoxidase, was evident. ML conditions induced increased photosynthesis rates and a further enhanced photoprotective potential for algae grown under BL and WL. In contrast, RL cultures exhibited no signs of acclimation towards increased irradiance. The data implicate that in diatoms the photoacclimation to high light intensities requires the perception of blue light.

Aureochrome 1a Is Involved in the Photoacclimation of the Diatom Phaeodactylum tricornutum

“…In a previous study we have shown that photoreceptors are involved in the processes of photoacclimation and photoprotection in diatoms [28]. Cultivation of P. tricornutum under low irradiance of BL induced the generation of a high light-adapted phenotype whereas a low light-adapted phenotype was observed for cultures grown under equivalent amounts of red light (RL).…”

High light stress triggers distinct proteomic responses in the marine diatom Thalassiosira pseudonana

“…We identified three aureochromes, which have been regarded as photoreceptors in P. tricornutum and T. pseudonana [39]. Under HL stress, no significant change was observed in relative abundance of aureochromes, suggesting that light signal transmission might be not regulated by change of expression abundance of aureochromes.…”

The Acclimation of Phaeodactylum tricornutum to Blue and Red Light Does Not Influence the Photosynthetic Light Reaction but Strongly Disturbs the Carbon Allocation Pattern

“…P. tricornutum UTEX 646 was grown as previously described in [15] in modified f/2 medium [46] with 16 g l −1 marine salt concentration and no silica. The cells were grown semi-continuously as airlift-cultures in a rectangular culture tank of 3 cm depth under illumination with either blue (465±10 nm) or red (660±10 nm) at light intensities of 24 and 40 µmol photons m −2 s −1 , respectively.…”

“…Recently, it was shown that BL is involved in the light acclimation of Phaeodactylum tricornutum [15]. They demonstrated that a typical HL phenotype with a reduced Chl a content per cell and a high photosynthetic capacity can be generated only in the presence of BL.…”