Chlorophyll fluorescence as a light signal enhances iron uptake by the marine diatom Phaeodactylum tricornutum under high-cell density conditions

Abstract Background Diatoms usually dominate phytoplankton blooms in open oceans, exhibiting extremely high population densities. Although the iron uptake rate of diatoms largely determines the magnitude and longevity of diatom blooms, the underlying mechanisms regulating iron uptake remain unclear....

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Autores principales:	Xuehua Liu, Xiujun Xie, Shan Gao, Lepu Wang, Lu Zhou, Yao Liu, Qiang Hu, Wenhui Gu, Guangce Wang
Formato:	article
Lenguaje:	EN
Publicado:	BMC 2021
Materias:	Chlorophyll fluorescence Density-dependent Iron uptake Biotic signal Biology (General) QH301-705.5
Acceso en línea:	https://doaj.org/article/e3f49648af81433988fca9e50ddcb727
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spelling	oai:doaj.org-article:e3f49648af81433988fca9e50ddcb7272021-11-28T12:41:13ZChlorophyll fluorescence as a light signal enhances iron uptake by the marine diatom Phaeodactylum tricornutum under high-cell density conditions10.1186/s12915-021-01177-z1741-7007https://doaj.org/article/e3f49648af81433988fca9e50ddcb7272021-11-01T00:00:00Zhttps://doi.org/10.1186/s12915-021-01177-zhttps://doaj.org/toc/1741-7007Abstract Background Diatoms usually dominate phytoplankton blooms in open oceans, exhibiting extremely high population densities. Although the iron uptake rate of diatoms largely determines the magnitude and longevity of diatom blooms, the underlying mechanisms regulating iron uptake remain unclear. Results The transcription of two iron uptake proteins, ISIP2a and ISIP1, in the marine diatom Phaeodactylum tricornutum was enhanced with increasing cell density, whereas the cellular iron content showed the opposite trend. When compared with the wild-type strain, knockdown of ISIP2a resulted in 43% decrease in cellular iron content, implying the involvement of ISIP2a in iron uptake under high-cell density conditions. Incubation of the diatom cells with sonicated cell lysate conditioned by different cell densities did not affect ISIP2a and ISIP1 expression, ruling out regulation via chemical cues. In contrast, ISIP2a and ISIP1 transcription were strongly induced by red light. Besides, chlorophyll fluorescence excited from the blue light was also positively correlated with population density. Subsequently, a “sandwich” illumination incubator was designed to filter out stray light and ensure that the inner layer cells only receive the emitted chlorophyll fluorescence from outer layers, and the results showed that the increase in outer cell density significantly elevated ISIP2a and ISIP1 transcription in inner layer cells. In situ evidence from Tara oceans also showed positively correlated between diatom ISIP transcripts and chlorophyll content. Conclusions This study shows that chlorophyll fluorescence derived from neighboring cells is able to upregulate ISIP2a and ISIP1 expression to facilitate iron assimilation under high-cell density. These results provide novel insights into biotic signal sensing in phytoplankton, which can help to elucidate the underlying mechanisms of marine diatom blooms.Xuehua LiuXiujun XieShan GaoLepu WangLu ZhouYao LiuQiang HuWenhui GuGuangce WangBMCarticleChlorophyll fluorescenceDensity-dependentIron uptakeBiotic signalBiology (General)QH301-705.5ENBMC Biology, Vol 19, Iss 1, Pp 1-15 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	Chlorophyll fluorescence Density-dependent Iron uptake Biotic signal Biology (General) QH301-705.5
spellingShingle	Chlorophyll fluorescence Density-dependent Iron uptake Biotic signal Biology (General) QH301-705.5 Xuehua Liu Xiujun Xie Shan Gao Lepu Wang Lu Zhou Yao Liu Qiang Hu Wenhui Gu Guangce Wang Chlorophyll fluorescence as a light signal enhances iron uptake by the marine diatom Phaeodactylum tricornutum under high-cell density conditions
description	Abstract Background Diatoms usually dominate phytoplankton blooms in open oceans, exhibiting extremely high population densities. Although the iron uptake rate of diatoms largely determines the magnitude and longevity of diatom blooms, the underlying mechanisms regulating iron uptake remain unclear. Results The transcription of two iron uptake proteins, ISIP2a and ISIP1, in the marine diatom Phaeodactylum tricornutum was enhanced with increasing cell density, whereas the cellular iron content showed the opposite trend. When compared with the wild-type strain, knockdown of ISIP2a resulted in 43% decrease in cellular iron content, implying the involvement of ISIP2a in iron uptake under high-cell density conditions. Incubation of the diatom cells with sonicated cell lysate conditioned by different cell densities did not affect ISIP2a and ISIP1 expression, ruling out regulation via chemical cues. In contrast, ISIP2a and ISIP1 transcription were strongly induced by red light. Besides, chlorophyll fluorescence excited from the blue light was also positively correlated with population density. Subsequently, a “sandwich” illumination incubator was designed to filter out stray light and ensure that the inner layer cells only receive the emitted chlorophyll fluorescence from outer layers, and the results showed that the increase in outer cell density significantly elevated ISIP2a and ISIP1 transcription in inner layer cells. In situ evidence from Tara oceans also showed positively correlated between diatom ISIP transcripts and chlorophyll content. Conclusions This study shows that chlorophyll fluorescence derived from neighboring cells is able to upregulate ISIP2a and ISIP1 expression to facilitate iron assimilation under high-cell density. These results provide novel insights into biotic signal sensing in phytoplankton, which can help to elucidate the underlying mechanisms of marine diatom blooms.
format	article
author	Xuehua Liu Xiujun Xie Shan Gao Lepu Wang Lu Zhou Yao Liu Qiang Hu Wenhui Gu Guangce Wang
author_facet	Xuehua Liu Xiujun Xie Shan Gao Lepu Wang Lu Zhou Yao Liu Qiang Hu Wenhui Gu Guangce Wang
author_sort	Xuehua Liu
title	Chlorophyll fluorescence as a light signal enhances iron uptake by the marine diatom Phaeodactylum tricornutum under high-cell density conditions
title_short	Chlorophyll fluorescence as a light signal enhances iron uptake by the marine diatom Phaeodactylum tricornutum under high-cell density conditions
title_full	Chlorophyll fluorescence as a light signal enhances iron uptake by the marine diatom Phaeodactylum tricornutum under high-cell density conditions
title_fullStr	Chlorophyll fluorescence as a light signal enhances iron uptake by the marine diatom Phaeodactylum tricornutum under high-cell density conditions
title_full_unstemmed	Chlorophyll fluorescence as a light signal enhances iron uptake by the marine diatom Phaeodactylum tricornutum under high-cell density conditions
title_sort	chlorophyll fluorescence as a light signal enhances iron uptake by the marine diatom phaeodactylum tricornutum under high-cell density conditions
publisher	BMC
publishDate	2021
url	https://doaj.org/article/e3f49648af81433988fca9e50ddcb727
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Chlorophyll fluorescence as a light signal enhances iron uptake by the marine diatom Phaeodactylum tricornutum under high-cell density conditions

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