| Artemisia sphaerocephala is a strong xerophyte which belongs to Compositae.It mainly distributes in desert region and sandy land of steppe region,and is an important windbreak and sand fixation plant.In this paper,A.sphaerocephalawas used as the research object,and the A.ordosica which also belongs to the sandy semi-shrub was used as a contrast.The characteristics of growth and physiological changes of two plants under different drought stress were discussed.The differentially expressed genes of A.sphaerocephalaunder different drought stress were obtained through the transcriptome sequencing technology,and the functional genes and regulatory genes related to drought resistance were filtered by annotation,and then the related characteristics of these genes were analyzed.The main results of the study are as follows:1.From the point of view of growth amount,the stem growth of the two plants decreased with the increase of water stress,and there was no significant difference between the super-severe water stress(SS)and the severe water stress(S),it indicated the severe stress had seriously affected the growth of A.sphaerocephala.From the point of view of stress symptom,the leaves of A.ordosicawere slightly wilted under the moderate water stress treatment(M),while A.sphaerocephala was almost unaffected;under severe treatment,the leaves of the base of A.ordosica began to turn yellow,while only the upper leaves of A.sphaerocephalawere wilted.Under super-severe steatment,the upper leaves of A.ordosica were seriously wilted,and the leaves of the base leaves were shedding,while the leaves of A.sphaerocephala were wilted and the base leaves began to turn yellow.It reflected that the A.sphaerocephalahad stronger drought resistance relative to A.ordosicaunder the same water stess.2.From the point of view of the water physiological index,A.sphaerocephalahad higher water content under the same stress treatment compared to the contrast plant,and its plasma membrane permeability was lower than A.ordosica,reflecting the less damage suffered.The changes of activity of SOD,POD and CAT in two plants under drought stress were similar to most of plants,which had no uniform and obvious change rule,this showed there is synergy in these enzymes in drought stress.The content of proline was significantly increased with severe and super-severe treatment,showing the positive response to drought stress,and the change of A.ordosica was greater than that of A.sphaerocephala.However,the changes of proline could only reflect the accumulation in response to the drought,but it was not suitable as the index of drought resistance.3.Twenty-five drought-related functional genes were filtered out from the differentially expressed genes which had partial homology with 15 species.The species with high homology with A.sphaerocephala were Chrysanthemum lavandulifolium,A.annua,Nicotiana tabacumand Helianthus annuus.The promoter elements are concentrated in the MYB binding site involved in drought-inducibility MBS,cis-acting element involved in defense and stress responsiveness TC-rich repeats and wounding and pathogen responsievness binds WRKY type transcription factors W-box.The expression of two P5 CS genes are all up-regulated,and consisitent with the results of the physiological test.One of the two genes related to trehalose synthesis was up-regulated and may be involved in drought resistance regulation.In the protective enzyme system,only POD and APX genes were found to be differentially expressed,but these genes were down-regulated.In the protective macromolecule material,only one of the eight differentially expressed genes of LEA protein was up-regulated,and the 9 genes of the aquaporin were all down-regulated and were related to the regulation of drought.4.Under different drought treatments,there were 37 differentially expressed genes related to five major drought resistance transcription factors genes in A.sphaerocephala,which had partial homology with 21 species.Further the species with high homology with A.sphaerocephala were A.annua,Chrysanthemum x morifolium and Chrysanthemum seticuspe f.boreale.Among these differentially expression genes,there are 15 belonging to AP2/EREBP,8 belonging to WRKY,10 belonging to MYB/MYC,2 belonging to bZIP and 2 belonging to NAC.The genes of transcriptional factors of AP2/EREBP,NAC,MYB/MYC were up-regulated and down-regulated as the drought stress.The 8 genes of transcriptional factors of WRKY were down-regulated as the drought stress.And two genes of bZIP transcription factor were up-regulated.Their mechanism of action and whether they are involved in drought control need further validation. |
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