| In order to study the coping mechanism of maize roots after drought treatment in depth,two inbred lines of maize drought-tolerant inbred lines 287M and drought-sensitive inbred lines 753F were used as experimental materials to study the physiological characteristics of maize seedlings under drought stress.The roots of different drought-treated maize were sequenced and the key genes related to drought stress were found by analyzing the sequencing results.The results are as follows:1.Semi-quantitative experiments to determine the time point of drought treatmentRNA was extracted from maize materials after drought treatment at different times and then reverse transcribed into cDNA.After using 18s rRNA gene as an internal control,transcriptional factors related to drought?ABI4 and CBF4?and drought-related functional genes?RD29B and RD22?were used for semi-quantitative experiment.Expression of ABI4 and CBF4 was significantly up-regulated after 24 h of drought treatment.Expression of RD29B and RD22 was high at 24 h and 48 h of drought treatment.So we determined the drought treatment time was 0 h,24 h,48 h and 72 h.2.Physiological characteristics of inbred lines after drought treatmentThe water content decreased significantly after natural drought treatment of maize seedlings.The root length of drought tolerant inbred line 287M was high than that of sensitive inbred line 753F.With the increase of drought treatment,the contents of O2-·and H2O2 increased in maize seedlings.The content of O2-·and H2O2 in the drought tolerant inbred line 287M was less than that of the drought sensitive inbred line 753F.At the same time,the change trend of SOD and APX activities in the two inbred lines was opposite to that of O2-·and H2O2.These results show that the growth of maize seedlings is affected by drought stress.But 287M shows tolerent to drought stress.3.Analysis of sequencing results of transcriptome after drought treatmentFrom the transcriptomic data after drought treatment,four drought-related metabolic pathways including secondary metabolism,ROS scavenging system,fatty acid metabolism,hormone metabolism,and drought-related transcription factors were analized.After comprehensive analysis of the genes in these pathways,the preliminary regulation network pathway of maize in response to early drought stress was obtained:Drought treatment caused the accumulation of ROS in plants and the accumulation of ROS could destroy the stability of cell membrane,which led to the increase of expression of unsaturated fatty acid-related genes in drought-tolerant inbred line 287M.The synthesis of metabolites,the high expression of genes related to ROS scavenging system,up-regulation of ABA,jasmonic acid and salicylic acid,led to the low expression of genes related to ethylene synthesis,which as a result decreased the synthesis of ethylene.The expression of transcription factors associated with secondary metabolism and root elongation growth were also up regulated in drought tolerant inbred line 287M.The expression level and the number of drought tolerance related genes in the drought-sensitive inbred line 753F were less than those in the drought tolerant inbred line 287M.These might the mechanism the287M showed resistance to drought stress. |
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