Abstract
Phosphorus (P) is a limiting macronutrient for diatom growth and productivity in the ocean. Much effort has been devoted to the physiological response of marine diatoms to ambient P change, however, the whole-genome molecular mechanisms are poorly understood. Here, we utilized RNA-Seq to compare the global gene expression patterns of a marine diatom Skeletonema costatum grown in inorganic P-replete, P-deficient, and inorganic- and organic-P resupplied conditions. In total 34,942 unique genes were assembled and 20.8% of them altered significantly in abundance under different P conditions. Genes encoding key enzymes/proteins involved in P utilization, nucleotide metabolism, photosynthesis, glycolysis, and cell cycle regulation were significantly up-regulated in P-deficient cells. Genes participating in circadian rhythm regulation, such as circadian clock associated 1, were also up-regulated in P-deficient cells. The response of S. costatum to ambient P deficiency shows several similarities to the well-described responses of other marine diatom species, but also has its unique features. S. costatum has evolved the ability to re-program its circadian clock and intracellular biological processes in response to ambient P deficiency. This study provides new insights into the adaptive mechanisms to ambient P deficiency in marine diatoms.
Highlights
IntroductionPhosphorus (P) is an essential macronutrient for phytoplankton growth and proliferation in the ocean (Dyhrman et al, 2007, 2012; White and Dyhrman, 2013; Feng et al, 2015), and its availability is often limiting for primary production (Dyhrman et al, 2007, 2012; Lin et al, 2012; White and Dyhrman, 2013; Feng et al, 2015)
Though there are no significant differences between Dissolved inorganic phosphorus (DIP)-resupplied and dissolved organic phosphorus (DOP)-resupplied groups according to physiological responses of S. costatum to ambient P variations (Figure 1), a considerable number of different Differentially expressed genes (DEGs) are identified between DOP-resupplied and DIP-resupplied groups (Figure 3)
The expression of genes encoding key photosynthetic proteins, such as photosystem II CP43, photosystem II cytochrome c550 and cytochrome b559, cytochrome b6-f complex iron-sulfur subunit and F-type H+-transporting ATPase, were all up-regulated significantly in P-deficient cells and down-regulated in both P-resupplied-4 h and P-resupplied-28 h cells (Supplementary Table S6). These results indicated that P-deficiency enhanced light harvesting and photosynthesis which might be an adaptive mechanism of S. costatum to ambient P deficiency
Summary
Phosphorus (P) is an essential macronutrient for phytoplankton growth and proliferation in the ocean (Dyhrman et al, 2007, 2012; White and Dyhrman, 2013; Feng et al, 2015), and its availability is often limiting for primary production (Dyhrman et al, 2007, 2012; Lin et al, 2012; White and Dyhrman, 2013; Feng et al, 2015). The capacity of phytoplankton to utilize DOP in a DIP-deficient ambient is essential to their success in the ocean
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