| In recent years,with the change of climate,the temperature of the facility greenhouse exceeds 40℃.High temperature stress（HTS）has become a major limiting factor for plant vegetable growth.Non-heading chinese cabbage is an important green leafy vegetable in China’s vegetable basket project.It is cool in nature,and when the temperature is too high,it will affect the yield and quality of non-heading chinese cabbage.Hydrogen peroxide（H2O2）is a signaling molecule of the plant reactive oxygen species（ROS）metabolic pathway in plants,which is widely involved in plant life activities and response to adversity and plays an important role in the ROS metabolic pathway.When heat-sensitive non-heading chinese cabbage was subjected to HTS,ROS accumulated leading to oxidative damage.It is important to investigate the pathway to alleviate oxidative damage in non-heading chinese cabbage by H2O2treatment and analyze its mechanism of action.In this study,the heat-sensitive variety’Jinpin Hanchun’and the heat-tolerant variety’Jinpin 1 Xia’were treated with HTS at 38°C and H2O2（0,0.1,0.5,1 and 10 mmol/L）to study the physiological response of different heat-tolerant The physiological response of different heat tolerant types of non-heading chinese cabbage.non-heading chinese cabbage was investigated,and the changes of ROS metabolism in leaves of’Jinpin Hanchun’were analyzed;the ROS-regulated gene Rboh family was mined through the Brassica genome database,and bioinformatics analysis of the gene family was conducted to reveal the mechanism of heat response regulation of Rboh genes in non-heading chinese cabbage.so as to provide a theoretical basis for genetic improvement of heat tolerant traits and facility cultivation management.Theoretical basis for genetic improvement of heat tolerance traits and facility cultivation management.The main results are as follows:1.Effect of HTS on the physiological characteristics of different varieties of non-heading chinese cabbageThe H2O2content,proline content,soluble sugar content,CAT and SOD activities of the non-heading chinese cabbage were significantly increased by the high temperature treatment for 12 h.The heat-sensitive varieties had higher activities.The relative water content decreased significantly;the MDA content and relative conductivity of the heat-sensitive variety’Jinpin Hanchun’increased significantly,while the soluble protein content and POD activity did not change significantly;compared with the heat-sensitive variety,the MDA content and relative conductivity of the heat-resistant variety’Jinpin 1 Xia’did not change significantly.Compared with the heat-sensitive variety,the MDA content and relative conductivity of the heat-tolerant variety’Jinpin 1 Xia’did not change significantly,and the soluble protein content and POD activity decreased significantly.The chlorophyll a content of leaves of heat-sensitive varieties decreased significantly after 12 h of high temperature treatment,while that of heat-resistant varieties did not change significantly.The actual photochemical efficiency and electron transfer rate were both on the rise,and the heat-sensitive varieties were larger than the heat-resistant ones.The maximum photochemical efficiency showed a decreasing trend,and the decreasing trend of the heat-sensitive variety was greater than that of the heat-resistant variety.It is presumed that HTS damaged the epidermal cell morphology of the leaves of heat-sensitive varieties,and the damage of cell membrane increased.The heat-tolerant varieties have higher osmoregulatory and antioxidant capacities,which effectively mitigate short-term high-temperature oxidative damage.2.Analysis of ROS metabolism in exogenous H2O2treated’Jinpin Hanchun’leavesAfter spraying H2O2treatment,HTS 12 h,POD,APX and MDHAR activities showed an increasing trend and CAT activity showed a decreasing trend with the increase of H2O2concentration.The MDA and H2O2contents showed a decreasing trend followed by an increasing trend,the ASA content increased rapidly and then remained stable,while the SOD,GR,TPX,DHAR activities,GSH and GSSG contents showed a rapid increase followed by a decreasing trend.The treatment with external application of 0.1 mmol/L H2O2reduced the leaf MDA and H2O2contents;increased the activities of SOD,POD,APX,MDHAR,DHAR,GR and TPX enzymes in the leaf mesoglutathione cycle,and increased the leaf ASA,GSH and GSSG contents.It was hypothesized that a concentration of 0.1 mmol/L H2O2increased the enzymatic activities and substances of the necrotropic glutathione cycle and decreased the MDA and H2O2contents to alleviate the damage of high temperature on’Jinpin Hanchun’.3.Analysis of biological information of Rboh gene family in non-heading chinese cabbageRespiratory burst oxidase（Rboh）is a key enzyme involved in ROS production and plays an important role in various biotic and abiotic stresses in plants.Fifteen Rboh genes（BcRboh A-BcRboh O）were identified based on the non-heading chinese cabbage genome.14 BcRboh proteins were predicted to be localized to cell membrane expression and one to the nucleus;BcRboh contains three conserved structural domains,an EF-hand structural domain and a transmembrane region;phylogenetic analysis showed that BcRboh is divided into four subfamilies,indicating The phylogenetic analysis showed that BcRboh was divided into four subfamilies,indicating potentially different functions and evolution;cis-acting elements were predicted using Plant CARE software,and the results showed that the four main categories included response to plant growth and development,response to adversity stress,light and phytohormones;the relative expression of 15 members was measured,and the results showed that BcRboh K gene expression was up-regulated in green peduncle leaves after pretreatment with 0.1 mmol/L H2O2.8gene expression levels were down-regulated and the remaining genes showed no significant changes;vector construction was performed for the significantly expressed BcRboh K.BcRboh K was observed to be expressed in the cell membrane in both tobacco and onion. |
