Functional Characterization Of Arabidopsis Zinc Finger Protein ZAT18 Responses To Drought Stress

Environmental stress poses a global threat to plant growth and reproduction,especially drought.Transcription factors play essential roles in response to various abiotic stresses.Zinc finger proteins which belong to TF III type transcription factors regulate downstream stress response genes against stress.In this dissertation,WT and ZAT18 OE lines were selected and assayed at the physiological and transcriptional levels under drought stress condition.The results were as following:(1)Subcellular location results revealed that ZAT18 protein was predominantly localized in the nucleus.ZAT18 was transcriptionally induced by many abiotic stress treatment,especially by drought and salt stress.ZAT18 preferentially expressed in stems,siliques and vegetative rosette leaves.(2)Germination assay showed that no significant difference was observed between ZAT18 transgenic and WT plants under normal growth condition.However,in the presence of 125 mM and 150 mM NaCl?200 mM and 300 mM mannitol,the ZAT18 OE lines showed decreased sensitivity when compared to WT plants during seed germination stage.(3)Overexpression of ZAT18 in Arabidopsis improved drought tolerance while mutation of zat18 resulted in decreased plant tolerance to drought stress.ZAT18 OE plants exhibited higher leaf water content and higher antioxidant enzyme activities,less leaf water loss,lower ROS content,EL and MDA after drought treatment when compared to WT.These results indicated that ZAT18 might act as a positive regulator during drought stress.(4)RNA sequencing analysis showed 423 and 561 genes were transcriptionally modulated by ZAT18 transgene before and after drought treatment,respectively.Pathway enrichment analysis indicated that hormone metabolism,stress,and signaling were over-represented in ZAT18 OE lines.Several stress responsive genes including COR47,ERD7,LEA6,RAS1 and hormone signaling transduction related genes including JAZ7 and PYL5 were identified as putative target genes of ZAT18.Taken together,ZAT18 functions as positive regulator and plays a crucial role in the plant response to drought stress.