Copper-induced increased expression of genes involved in photosynthesis, carotenoid synthesis and C assimilation in the marine alga Ulva compressa

Eduardo Castro-Nallar,Claudio Meneses,Alberto González,Alejandra Moenne,Juan Pablo Huidobro-Toro,Katterinne N Mendez,Daniel Laporte,Felipe E Rodríguez

doi:10.1186/s12864-018-5226-4

Eduardo Castro-Nallar, Claudio Meneses + Show 6 more

Open Access

https://doi.org/10.1186/s12864-018-5226-4

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Abstract

BackgroundThe marine alga Ulva compressa is the dominant species in coastal areas receiving effluents from copper mines. The alga can accumulate high amounts of copper and possesses a strong antioxidant system. Here, we performed short-term transcriptomic analyses using total RNA of the alga cultivated with 10 μM of copper for 0, 3, 6, 12 and 24 h by RNA-seq.ResultsDe novo transcriptomes were assembled using the Trinity software, putative proteins were annotated and classified using Blast2GO. Differentially expressed transcripts were identified using edgeR. Transcript levels were compared by paired times 0 vs 3, 0 vs 6, 0 vs 12 and 0 vs 24 h at an FDR < 0.01 and Log2 Fold Change > 2. Up-regulated transcripts encode proteins belonging to photosystem II (PSII), Light Harvesting II Complex (LHCII), PSI and LHCI, proteins involved in assembly and repair of PSII, and assembly and protection of PSI. In addition, transcripts encoding enzymes leading to β-carotene synthesis and enzymes belonging to the Calvin-Benson cycle were also increased. We further analyzed photosynthesis and carotenoid levels in the alga cultivated with 10 μM of copper for 0 to 24 h. Photosynthesis was increased from 3 to 24 h as well as the level of total carotenoids. The increase in transcripts encoding enzymes of the Calvin-Benson cycle suggests that C assimilation may also be increased.ConclusionsThus, U. compressa displays a short-term response to copper stress enhancing the expression of genes encoding proteins involved in photosynthesis, enzymes involved carotenoids synthesis, as well as those belonging to the Calvin-Benson cycle, which may result in an increase in C assimilation.

Highlights

The marine alga Ulva compressa is the dominant species in coastal areas receiving effluents from copper mines
U. compressa transcriptomes: Assembly, annotation, and classification of transcripts Sequencing of cDNA libraries prepared from U. compressa cultivated without copper (0 h, control) resulted in 11.4 M of reads and those prepared from the alga cultivated with 10 μM copper for 3, 6, 12 and 24 h resulted in 18.4 M of reads on average (Table 1)
The potassium antiporter KEA1, required for photosystem I (PSI) formation, UPF0187, involved in the stabilization of PSI, TAB2, involved in translation of PsaB, the kinase STN7, involved in phosphorylation of the Light Harvesting Complex II (LHCII) that allows its migration of subunits of Photosystem II (PSII) to PSI, and the phosphatase PPH1 (2C57), involved in the dephosphorylation of LHCII that increase the Transcripts with increased levels encode enzymes involved in carotenoid synthesis and the Calvin-Benson cycle The level of transcripts encoding the enzymes geranylgeranyl diphosphate synthase (GGDS), an enzyme that synthesize geranylgeranyl pyrophosphate; phytoene synthase (PS), that synthesize phytoene; phytoene desaturase (PD), that synthesize ϛ-carotene; carotene desaturase (CD), that synthesize lycopene, and lycopene β-cyclase (LC), that synthesize β-carotene were increased (Table 3)

Summary

Introduction

The marine alga Ulva compressa is the dominant species in coastal areas receiving effluents from copper mines. We performed short-term transcriptomic analyses using total RNA of the alga cultivated with 10 μM of copper for 0, 3, 6, 12 and 24 h by RNA-seq. Heavy metals such as zinc, iron, copper, and manganese are essential for plant cell viability since they are associated with proteins and enzymes such as superoxide dismutase, plastocyanin, cytochrome c oxidase, amino oxidase, polyphenol oxidase, nitrogenase, and several dehydrogenases and oxidases [1, 2]. Rice plants cultivated with copper concentrations from 30 nM to 98 μM for 30 days displayed an inhibition of photosynthesis above 157 nM mostly due to inhibition of PSII and decrease in ATP synthase activity [6]. It appears that plants do not tolerate copper concentrations higher than 100–200 nM due to an inhibition of photosynthesis

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