Physiological Response And Transcriptomics Of Abutilon Theophrasti Under Cadmium Stress

In order to study the effects of cadmium stress on the physiological and molecular mechanisms of Abutilon theophrasti,this study was based on the hydroponic cultivation of Abutilon mallow for 40 days,through the setting of 1,5,10,15,20 mg/L cadmium stress group and 0 mg/L blank control group,respectively,after the 1,3,5,7 and 9 day of stress to collect the root and leaf of Abutilon mallow to detect physiological indicators,as well as the root and leaf cadmium content and subcellular cadmium content.In order to investigate more deeply the molecular mechanism of Abutilon mallow in response to Cd stress,the experiment was conducted by RNA-seq technology to analyze the transcriptome sequencing of Abutilon mallow roots and leaves under 15 mg/L Cd stress at day 9.The main findings are as follows.1.Abutilon mallow root and leaf showed an overall consistent change in H₂O₂ content and CAT activity expression in response to Cd stress,while POD and SOD showed different trends in different parts of the plant.2.In the ascorbic acid-glutathione cycle（ASA-GSH）,the ASA,GSH and GSSG contents in most of the stress groups in the leaves of Abutilon mallow were lower than those of the blank control,while the enzyme activity expression of GPX and APX in the stress groups were higher than those of the blank.The ASA,GSH and GSSG contents in most of the stress groups in the root system of Abutilon mallow were significantly higher than the blank control and increased with time.Only APX activity of the three circulating enzymes in the root system was not significantly different from the blank group in most of the stress groups,and GPX expression in the root stress group was higher than the blank control while GR enzyme activity was lower than the blank group.3.The Cd content in the leaves and roots of Abutilon mallow increased with increasing stress time and concentration,the highest dry weight Cd content in leaves did not exceed 250mg/L while the dry weight Cd content in most of the root stress groups was significantly higher than 250 mg/L.The proportional analysis of cadmium content of subcellular fractions in the roots and leaves of Abutilon indicus showed that the cell-soluble fraction of cadmium in the roots and leaves under cadmium stress was the most abundant,followed by the cell wall,and the organelle fraction contained the least amount of cadmium.4.Analysis of the transcriptome results of Abutilon mallow leaves after 9 days of cadmium stress at 15 mg/L showed that 5518 genes were detected in the leaves,of which 4459 genes were significantly differentially expressed.The main pathways enriched by GO and KEGG included photosynthetic,detoxification,antioxidant,carbon metabolism,and signal transduction with phytohormones pathways.Root transcriptome analysis showed a detected87,639 genes,differential genes contained 6347,and the analysis by GO and KEGG enrichment revealed that Abutilon root system mainly responded to Cd stress through detoxification,transporter activity,antioxidant activity,Phenylpropanoid biosynthesis,membrane transport and other pathways.5.By randomly selecting 10 significantly differentially expressed genes in each root and leaf by q RT-PCR and correlating with the transcriptome data,the results showed that the correlation coefficients R² were greater than 0.9 in both root and leaf of Abutilon,which proved that the transcriptome data were reliable and available.In conclusion,Abutilon mallow showed good tolerance to Cd.Although Cd stress inhibited photosynthesis and basal metabolism of Abutilon mallow,Abutilon mallow mitigated the oxidative damage caused by Cd at the physiological level by up or maintain the activities of enzymes in antioxidant and ASA-GSH cycle,at the molecular level by transport and secondary metabolism in response to Cd stress.