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

BMC Biology

Xiujun Xie¹  Shan Gao¹  Guangce Wang¹  Wenhui Gu¹  Lu Zhou²  Xuehua Liu²  Lepu Wang²  Qiang Hu³  Yao Liu⁴ 

[1] CAS and Shandong Province Key Laboratory of Experimental Marine Biology, Center for Ocean Mega-Science, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China;Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China;CAS and Shandong Province Key Laboratory of Experimental Marine Biology, Center for Ocean Mega-Science, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China;Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China;College of Earth Sciences, University of Chinese Academy of Sciences, Beijing, China;Institute for Advanced Study, Shenzhen University, Shenzhen, China;Public Technology Service Center, Institute of Oceanology, Chinese Academy of Sciences, 266071, Qingdao, China;

关键词: Chlorophyll fluorescence;    Density-dependent;    Iron uptake;    Biotic signal;   

DOI  :  10.1186/s12915-021-01177-z

来源: Springer

【 摘 要 】

BackgroundDiatoms 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.ResultsThe 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.ConclusionsThis 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.

【 授权许可】

CC BY