Adaptation Study Of Hypnum Plumaeforme To Different Concentrations Of Cerium Stress Treatment

Baiyun Obo mining area in Baotou,Inner Mongolia is the most important rare earth mining area in China,mainly rich in cerium,praseodymium and other rare earth elements,the area is arid with little rainfall,poor soil and serious heavy metal pollution.Mosses are a kind of water-changing plants,which can adapt to a variety of habitats and play an important role in preserving water and preventing soil erosion.With simple structure,mosses have strong ability to absorb and enrich heavy metals and rare earth elements in the substrate,and play an important role in monitoring and managing heavy metal pollution in mining areas and in revegetation and reconstruction of ecosystems.Hypnum plumaeforme is widely distributed,with strong adaptability and heavy metal enrichment ability,and can be cultivated in large scale artificial culture.The changes of photosynthetic pigments of Hypnum plumaeforme under heavy metal stress,monitoring of atmospheric heavy metal pollution and extraction of post-like substances in vivo have been studied,but little research has been reported on the adaptability of Hypnum plumaeforme under cerium（Ce）stress.Therefore,this experiment was conducted to investigate the effect of Ce on the growth of Hypnum plumaeforme through the analysis of physiological and biochemical indexes and transcriptome data of Hypnum plumaeforme under different Ce treatments,and also to lay the foundation for further research on Hypnum plumaeforme for ecological restoration of mining areas and for rare earth element indication.The specific results of the study are as follows.1.The biomass,gametophyte length,branching number and relative water content of Hypnum plumaeforme showed a trend of increasing and then decreasing with increasing treatment concentrations under five different CeCl₃ solutions（0,10,50,100and 300 mg/kg）,and all of them reached the maximum value at the treatment concentration of 50 mg/kg,indicating that this treatment concentration significantly promoted the growth and development of Hypnum plumaeforme.2.Under different concentrations of Ce treatment,the trends of chlorophyll content,enzymatic system in antioxidant system and osmoregulatory substances of Hypnum plumaeforme were all consistent,when the treatment concentration gradually increased,the overall were rising first and then decreasing,and these physiological indexes all reached the maximum when the treatment concentration was 50 mg/kg,indicating that Hypnum plumaeforme could reduce the toxic effects of excess cerium to maintain its growth and development by improving its photosynthetic efficiency,enzyme activity and maintaining the osmotic balance inside and outside the cell under certain concentration of Ce stress treatment.3.By sequencing the transcriptome of 15 samples under the five concentration treatments,it can be seen from the analysis of the sequencing results that a total of105.54 Gb Clean Data was obtained,yielding 134,813 unigenes.The most DEGs were screened under the treatment with Ce of 50 mg/kg compared to the control group,with a total of 10,354,and at this concentration of treatment,the up-regulated genes played a dominant role.By KEGG enrichment,the analysis revealed that most of the DEGs were significantly enriched in these pathways of phenylpropanoid biosynthesis,phytohormone signaling,flavonoid biosynthesis,oleuropein lactone biosynthesis and photosynthesis,and DEGs were found to be mainly enriched in metabolic pathways,indicating that in response to different levels of Ce stress,the regulation of genes in the secondary metabolic pathway plays an important role in the growth and development of Hypnum plumaeforme.The differentially expressed genes encoding HSP and SOD were significantly up-regulated,indicating that increasing the antioxidant level in vivo is also one of the important mechanisms to enhance Ce tolerance in Hypnum plumaeforme.In this study,the transcriptome of Hypnum plumaeforme treated with different Ce concentrations was sequenced for the first time.The growth,physiological,biochemical and transcriptomic results illustrated the dynamic response mechanism of Hypnum plumaeforme to Ce stress,which provides valuable information for better understanding of Hypnum plumaeforme in response to Ce stress,and lays a good foundation for its subsequent research on Hypnum plumaeforme for ecological restoration of rare earth mining areas and for rare earth element prospecting indication.