The Study Of Exogenous Nitric Oxide Affecting Waterlogging Resistance Of Malus Halliana Koehne

Malus halliana Koehne has a beautiful tree shape and colorful flowers,with high ornamental value,edible value and medicinal value,but its tolerant to waterlogging stress is low,the root of potted Malus halliana Koehne is easy to rot under waterlogging condition.With the deterioration of environmental conditions,the phenomenon of waterlogging in the middle and lower reaches of the Yangtze River has become more serious,and the Malus halliana Koehne plantation industry in Jiangsu Province has been seriously affected by waterlogging.As a stress-resistance signal molecule,nitric oxide has been proved to improve waterlogging resistance in many crops,vegetables,and flowers,but the research on the molecular regulation mechanism of nitrogen monoxide in waterlogging resistance of Malus halliana Koehne is still in blank.In this study,two-year-old seedlings of Malus halliana Koehne were used as materials,and the treatments were SNP,cPTIO and ddH2O treatment(control group).The high-throughput transcriptome sequencing technology was used to detect and compare the expression level changes of differentially expressed genes between different treatments under waterlogging stress;based on this,the contents of phytohormones such as abscisic acid and ethylene,chlorophyll content,antioxidant enzyme activity,malondialdehyde and proline content in different treatments under waterlogging stress were measured and compared.The purpose of this study is to reveal the molecular regulatory mechanism of nitric oxide affecting the waterlogging tolerance of Malus halliana Koehne,to clarify its regulatory pathway,and to lay the theoretical foundation and experimental basis for the research on the waterlogging tolerance of Malus halliana Koehne.The main findings are as follows:1.Based on the Illumina HiSeq 4000 sequencing platform,transcriptome sequencing was performed on the leaves of the SNP treatment group,cPTIO treatment group,and ddH2O treatment group after 24 hours of waterlogging stress.The results showed that the effective data amounts were 7.39G,6.60G,and 6.93G,respectively.The quality evaluation showed that the quality of the three transcriptome libraries was good,the gene interruption had a good randomness,reads were evenly distributed in all parts of the gene,and the library expression levels were high,the quantitative was accurate.The total number of differentially expressed genes(DEG)in the 3 transcriptome libraries was 2671,3044,and 2835,respectively;volcano plot analysis showed that the cPTIO vs ddH2O group had the most significantly down-regulated DEG,and the SNP vs cPTIO group had the most significantly up-regulated DEG.GO classification showed that 1467 DEGs in the SNP vs ddH2O alignment group were related to water stress,and 1249 DEGs were related to protein ubiquitination.GO enrichment analysis showed significant differences in DEG expression in anaerobic respiration,ethylene,and abscisic acid.KEGG annotation analysis shows that DEGs were mainly distributed in carbohydrate metabolism pathway,signal transduction pathway,and amino acid metabolism pathway.Interaction system network analysis showed that nitric oxide significantly affected the expression of genes related to abscisic acid and ethylene synthesis.2.Determination of phytohormone content in leaves of SNP treated group,cPTIO treated group and ddH2O treated group under waterlogging stress for 5 days,10 days and 15 days was carried out,the results showed that exogenous nitric oxide can positively regulate the mechanism of nitric oxide synthesis in Malus halliana Koehne leaves under waterlogging stress through the NOS synthesis pathway,which is consistent with the expression of NOS synthetase-related genes in transcriptome sequencing results.Nitric oxide promoted the accumulation of ABA in Malus halliana Koehne under waterlogging stress,transcriptome sequencing results also showed that the expression of related genes in ABA synthesis mechanism and metabolism mechanism in Malus halliana Koehne is regulated by exogenous NO,indicating that NO can positive regulate ABA Synthesis in Malus halliana Koehne.Nitric oxide inhibited the ethylene content in the leaves of Malus halliana Koehne under waterlogging stress,transcriptome data showed that the expression of ethylene-related genes in Malus halliana Koehne leaves was also significantly reduced,indicating that NO can negatively regulate the ethylene synthesis in Malus halliana Koehne,we speculated that this was to suppress the formation of adventitious roots caused by waterlogging stress and avoid excessive consumption of energy and materials under abiotic stress.3.Determination of ROS scavenging system in leaves of SNP treated group,cPTIO treated group and ddH2O treated group under waterlogging stress for 5 days,10 days and 15 days was carried out,the results showed that nitric oxide inhibited MDA content in Malus halliana Koehne leaves under waterlogging stress,increased proline content,and enhanced enzyme activities of SOD,POD,and CAT,transcriptome data also showed that the expression of related genes in the antioxidant enzyme synthesis pathway increased significantly,which indicated that NO can protect the ROS scavenging system in Malus halliana Koehne,and effectively inhibit the excessive accumulation of active oxygen,and reduce the damage caused by waterlogging stress on Malus halliana Koehne.