Comparative transcriptional profiling of <i>Gracilariopsis lemaneiformis</i> in response to salicylic acid- and methyl jasmonate-mediated heat resistance

<div><p>Culturing the economically important macroalga <i>Gracilariopsis lemaneiformis</i> (Rhodophyta) is limited due to the high temperatures in the summertime on the southern Chinese coast. Previous studies have demonstrated that two phytohormones, salicylic acid (SA) and methyl jasmonate (MJ), can alleviate the adverse effects of high-temperature stress on <i>Gp</i>. <i>lemaneiformis</i>. To elucidate the molecular mechanisms underlying SA- and MJ-mediated heat tolerance, we performed comprehensive analyses of transcriptome-wide gene expression profiles using RNA sequencing (RNA-seq) technology. A total of 14,644 unigenes were assembled, and 10,501 unigenes (71.71%) were annotated to the reference databases. In the SA, MJ and SA/MJ treatment groups, 519, 830, and 974 differentially expressed unigenes were detected, respectively. Unigenes related to photosynthesis and glycometabolism were enriched by SA, while unigenes associated with glycometabolism, protein synthesis, heat shock and signal transduction were increased by MJ. A crosstalk analysis revealed that 216 genes were synergistically regulated, while 18 genes were antagonistically regulated by SA and MJ. The results indicated that the two phytohormones could mitigate the adverse effects of heat on multiple pathways, and they predominantly acted synergistically to resist heat stress. These results will provide new insights into how SA and MJ modulate the molecular mechanisms that counteract heat stress in algae.</p></div

DataSheet_1_Transcriptome analysis reveals ABA involved in the detoxification mechanism of macroalga Gracilariopsis lemaneiformis to cadmium toxicity.xlsx

IntroductionCadmium (Cd) is a significant threat environmental pollutant in the marine ecological environment offshore. The macroalga, Gracilariopsis lemaneiformis, of significant economic value, is widely cultivated along China’s coastline. Yet, little is known about the molecular mechanisms underlying Cd tolerance in macroalga.MethodsHere, we examined the transcriptome of G. lemaneiformis exposed to Cd to identify the responses to Cd stress.Results and discussionOur findings revealed that Cd led to the retardation of growth rate in G. lemaneiformis, accompanied by a notable reduction in the content of photosynthetic pigments and a decrease in the expression of genes associated with the photosynthetic system and nitrogen metabolism. When exposed to Cd, there was a rapid increase in Cd levels through the upregulation of genes encoding GlZIP6 and GlIRT1. Additionally, the expression of Cd efflux transporters, GlZIP1 and GlABCG22, and the ABCC7 transporter for compartmentation to the vacuole, was induced to mitigate Cd toxicity. Cd also activated crucial genes involved in the ABA biosynthesis and enhanced ABA content, thereby inducing ABA signaling pathway. Furthermore, exogenous ABA reduced the growth inhibition of G. lemaneiformis under Cd stress. Redox homeostasis was adjusted to adapt to Cd toxicity, with thioredoxin, glutaredoxin cycle and ascorbate-glutathione cycle identified as playing significant in maintaining reactive oxygen species homeostasis. Moreover, transcription factors such as several MYBs, signal transmission factors G protein and heat shock proteins (sHSPs, HSP 40, HSP 90, HSP101) were involved in the detoxification of Cd. Collectively, this study provided a comprehensive understanding of the molecular mechanisms underpinning the of responses of macroalga G. lemaneiformis to Cd exposure.</p

DataSheet_2_Transcriptome analysis reveals ABA involved in the detoxification mechanism of macroalga Gracilariopsis lemaneiformis to cadmium toxicity.docx

IntroductionCadmium (Cd) is a significant threat environmental pollutant in the marine ecological environment offshore. The macroalga, Gracilariopsis lemaneiformis, of significant economic value, is widely cultivated along China’s coastline. Yet, little is known about the molecular mechanisms underlying Cd tolerance in macroalga.MethodsHere, we examined the transcriptome of G. lemaneiformis exposed to Cd to identify the responses to Cd stress.Results and discussionOur findings revealed that Cd led to the retardation of growth rate in G. lemaneiformis, accompanied by a notable reduction in the content of photosynthetic pigments and a decrease in the expression of genes associated with the photosynthetic system and nitrogen metabolism. When exposed to Cd, there was a rapid increase in Cd levels through the upregulation of genes encoding GlZIP6 and GlIRT1. Additionally, the expression of Cd efflux transporters, GlZIP1 and GlABCG22, and the ABCC7 transporter for compartmentation to the vacuole, was induced to mitigate Cd toxicity. Cd also activated crucial genes involved in the ABA biosynthesis and enhanced ABA content, thereby inducing ABA signaling pathway. Furthermore, exogenous ABA reduced the growth inhibition of G. lemaneiformis under Cd stress. Redox homeostasis was adjusted to adapt to Cd toxicity, with thioredoxin, glutaredoxin cycle and ascorbate-glutathione cycle identified as playing significant in maintaining reactive oxygen species homeostasis. Moreover, transcription factors such as several MYBs, signal transmission factors G protein and heat shock proteins (sHSPs, HSP 40, HSP 90, HSP101) were involved in the detoxification of Cd. Collectively, this study provided a comprehensive understanding of the molecular mechanisms underpinning the of responses of macroalga G. lemaneiformis to Cd exposure.</p

COG functional classification of the unigenes.

<p>COG functional classification of the unigenes.</p

Species distribution of the unigenes against the NR database.

<p>The percentages in the pie chart represent the <i>Gp</i>. <i>lemaneiformis</i> genes that are homologous to those of other species.</p

KEGG analysis of the synergistic genes regulated by SA and MJ in <i>Gp</i>. <i>Lemaneiformis</i>.

<p>KEGG analysis of the synergistic genes regulated by SA and MJ in <i>Gp</i>. <i>Lemaneiformis</i>.</p

The DEG number and expression profile clustering analysis.

<p><b>(A)</b> Venn diagram of the DEGs. The number of DEGs in the SA, MJ and SA/MJ treatment groups were relative to those in the CK group. <b>(B)</b> Heat map of the DEGs after pairwise comparisons between the four different groups. Each column represents one treatment group, and each row represents one unigene. The colors indicate the expression values scaled to standard deviations and centered at the normal intensity level (Z-score). Red indicates increased expression relative to the control conditions, and green indicates decreased expression.</p

GO categories of the unigenes.

<p>The unigenes were annotated to three categories: biological process, cellular component, and molecular function. The abscissa represents the GO category. The left and right ordinates represent percentage and number of the unigenes, respectively.</p

Statistical results from the sequencing data.

<p>Statistical results from the sequencing data.</p

Distribution of pathway numbers against the KEGG database.

<p>The top 20 most abundant KEGG pathways were shown.</p