Effects And Mechanism Of Uniconazole On Alleviating Low Temperature Stress In Mung Bean At The First Flowering Date

The initial flowering stage is a complex stage in which mung beans respond to low temperature stress.Low temperature stress will limit the assimilation,distribution and transfer of carbon in mung beans,and ultimately affect the yield formation of mung beans.Uniconazole（S3307）,as a plant growth regulator,can directly or indirectly participate in a series of metabolic processes of crops to deal with abiotic stresses so as to improve crop resistance and increase yield.In order to clarify the effect of low temperature stress on mung bean at the initial flowering stage and the regulatory effect and molecular mechanism of S3307,the test materials in this study are mung bean Lvfeng 2（L2）and Lvfeng 5（L5）,and a low temperature of 15℃at the initial flowering stage Under stress treatment,leaf spray S3307 was used as a control method.Potted experiments were used to parallelly determine the yield composition,carbon metabolism-related indicators,osmotic adjustment substance content,active oxygen and scavenging systems,and photosynthetic-related physiological and biochemical indicators of the two mung bean varieties,and use the transcriptome Comparative analysis of possible regulatory mechanisms by science and metabolomics,and study the regulatory effects and molecular mechanisms of S3307 on mung bean at the initial flowering stage under low temperature stress.The main results and conclusions are as follows:1.The low temperature stress treatment of mung bean at the initial flowering stage resulted in the reduction of the photosynthetic capacity of the leaves of the two varieties of mung bean and hindered the process of carbohydrate synthesis.After S3307 treatment,the net photosynthetic rate（Pn）in the leaves of L2 and L5 increased,which improved the photosynthetic gas exchange parameters（transpiration rate,stomatal conductance,intercellular CO₂concentration）in the leaves of the two varieties of mung bean,and significantly increased the photosynthetic pigment Content（chlorophyll a,chlorophyll b,total chlorophyll,carotenoids）,and increase the activity of key carbon metabolism enzymes（neutral invertase NI,acid invertase AI,sucrose synthase SS,sucrose phosphate synthase SPS）,and increase carbohydrate The content of compounds（sucrose,starch）increases the level of carbon assimilation and transport;after the low temperature stress is relieved,the above-mentioned indicators all show the opposite trend to the change during the stress period.2.After low temperature stress treatment,the content of active oxygen in the leaves of mung bean L2 and L5 increased,the content of malondialdehyde（MDA）increased significantly,superoxide dismutase（SOD）,peroxidase（POD）,and ascorbate peroxidase（APX）,glutathione reductase（GR）activity increased,catalase（CAT）activity decreased,ascorbic acid（As A,DHA）,glutathione（GSH,GSSG）content increased.After spraying S3307 treatment,the above-mentioned increase of active oxygen content and MDA content was relieved,the protective enzyme activity was enhanced,and the further increase of ascorbic acid and glutathione content was slowed down,but it was still higher than the control（CK）treatment;it returned to normal After temperature management,the above-mentioned indicators showed the opposite trend of change from the period of low temperature stress.3.After low temperature stress,the content of soluble sugar,soluble protein and proline in the leaves of mung bean L2 and L5 increased.After spraying S3307,the contents of the above-mentioned osmotic adjustment substances in the L2 and L5 leaves can be further increased.After the normal temperature management was restored,the above-mentioned osmotic adjustment substance indicators showed the opposite trend to the stress period.4.Low temperature stress leads to the decrease of the number of pods per plant,the number of seeds per plant,and the weight of 100 seeds in the leaves of L2 and L5,which ultimately leads to a decrease in yield,and during the 1-4 days of stress,the yield gradually shows a decreasing trend.Within 4 days of low temperature stress,the yields of L2 and L5 were reduced by 13.31%,21.66%,36.25%,58.25%and 8.53%,19.50%,32.61%,46.60%,respectively,compared with the respective controls.The yield of L2 is greater than that of L5,indicating that L2 is more sensitive to low temperature stress.After spraying S3307,the yields of L2 and L5 were increased by8.06%,12.13%,6.36%,20.12%and 4.42%,13.42%,1.00%,10.65%,respectively,compared with the stress treatment,indicating that spraying S3307 after low temperature stress is effective Alleviate the damage caused by low temperature stress to mung bean,and then alleviate the serious decline in yield caused by stress.5.Transcriptome analysis showed that compared with low temperature treatment,mung bean leaves sprayed with S3307 under normal temperature and low temperature stress jointly up-regulated and down-regulated 27 and 11 genes,respectively.Among the up-regulated genes,there are functional genes directly and indirectly involved in carbohydrate metabolism.The analysis of metabolome results showed that in the pairwise comparison of CK/D and D+S/D,there were 16 and 67 metabolites jointly up-regulated and down-regulated by mung bean leaves,and most of the up-regulated metabolites belonged to lipids and carbohydrates.The compound further reveals that S3307 can improve the carbon metabolism level of mung bean and the ability to resist low temperature.The combined analysis of the transcriptome and metabolome showed that S3307 promotes the ASD1 gene and URGT4 under low temperature stress by regulating the pathways of amino sugar and nucleotide sugar metabolism and galactose metabolism in mung bean.The increase in expression increases the content of carbohydrates such as N-acetyluric acid and lactose,and ultimately improves the cold resistance of mung beans.