Detoxification strategies and regulation of oxygen production and flowering of Platanus acerifolia under lead (Pb) stress by transcriptome analysis

Abstract

Toxic metal pollution is a major environmental problem that has received wide attention. Platanus acerifolia (London plane tree) is an important greening tree species that can adapt to environmental pollution. The genetic basis and molecular mechanisms associated with the ability of P. acerifolia to respond lead (Pb) stress have not been reported so far. In this study, 16,246 unigenes differentially expressed unigenes that were obtained from P. acerifolia under Pb stress using next-generation sequencing. Essential pathways such as photosynthesis, and gibberellins and glutathione metabolism were enriched among the differentially expressed unigenes. Furthermore, many important unigenes, including antioxidant enzymes, plants chelate compounds, and metal transporters involved in defense and detoxification mechanisms, were differentially expressed in response to Pb stress. The unigenes encoding the oxygen-evolving enhancer Psb and OEE protein families were downregulated in Pb-stressed plants, implying that oxygen production might decrease in plants under Pb stress. The relationship between gibberellin and P. acerifolia flowering is also discussed. The information and new insights obtained in this study will contribute to further investigations into the molecular regulation mechanisms of Pb accumulation and tolerance in greening tree species.

Transcriptomic and physiological analyses of Medicago sativa L. roots in response to lead stress

“…The GO term and KEGG enrichment analyses showed that terms for transport (GO:0006810) and membrane (GO:0016020, GO:0031224) (S3 Table), and pathways related to signal (ko03320, ko04075) and energy metabolism (ko00040, ko00020, ko00196, ko00010) (Table 3), were significantly enriched in the identified DEGs. These results were in agreement with previous studies that reported that heavy metals damaged plant membrane systems, inhibited photosynthesis, and delayed plant growth [27, 38–40]. …”

“…Previous studies have shown that photosynthesis is sensitive to heavy metal stress [27]. In this study, the KEGG pathways for “photosynthesis—antenna proteins” (ko00196) were significantly enriched in Pb-stress cDNA libraries (Table 3), in which the expression levels of 10 DEGs coding for chlorophyll a/b-binding protein (light-harvesting complex I protein) were significantly upregulated (S5 Table).…”

“…sativa . Glutathione is one of the most important plant antioxidants and is also a substrate for phytochelatins, which are metal-chelating compounds that enable metal tolerance [4, 27]. We identified 15 DEGs coding for glutathione S-transferase (GST) in the “glutathione metabolism” (ko00480) pathway (S5 Table).…”

“…Photosynthesis is the most important biological process for plants, and heavy metals like Pb inhibit photosynthesis by decreasing the chlorophyll content and number of chloroplasts, and disrupting chloroplast structure [27, 47, 48]. The chloroplast chlorophyll a/b-binding protein is an essential factor in photosynthesis that participates in the two key processes of light absorption and electron transfer [27, 49].…”

“…Genes involved in heavy metal responses have been widely studied in different plant species [15, 21–24]; however, the genome-wide network for gene expression and interactions in response to heavy metals are still relatively unknown. Recent studies using next-generation sequencing technology identified a number of microRNAs and their corresponding targets, which were genes whose expression is sensitive to heavy metal stress [20, 25–27]. These findings indicate that the response induced by heavy metals in plants is a complex network that involves diverse physiological processes and metabolic pathways.…”