Molecular Mechanism Of Transcription Factor OsSPL4 In Response To Drought Stress In Rice

With global warming,drought occurs frequently in recent years.Especially,because of the large water demand for the growth and development of rice,water shortage easily leads to the reduced plant tillering,a hindered flower organ development,an insufficient grain filling,and eventually results in a reduced rice yield.Transcription factors play an important molecular ecological function in responding to the abiotic stress,and our previous research have found that transcription factor OsSPL4 of rice significantly affects the resistance to drought stress.However,the molecular ecological function of OsSPL4 involved in the drought stress has been not elucidated.Thus,in order to systematically explore the molecular ecological role of transcription factor OsSPL4 in rice drought stress response,the osspl4 mutants,OsSPL4-OE plants,and their wild-type ZH11 rice were employed to investigate the physiological and ecological characteristics in response to drought stress.Furthermore,the molecular ecological function of transcription factor OsSPL4 in rice drought stress were also investigated by the molecular biological technologies.The main results obtained are as follows:1.The phenotypes of three genotype rice seedlings under the drought and ABA stress were investigated.The results showed that osspl4 mutants exhibited a better growth than wild-type ZH11 and OsSPL4-OE plants,while OsSPL4-OE plants had the worst growth potential.The physiological results showed that MDA contents of the leaves of osspl4 mutants were significantly lower than those of OsSPL4-OE plants and wild-type ZH11,while the activities of antioxidant enzymes SOD,POD and CAT in the leaves of osspl4 mutants were significantly higher than those in OsSPL4-OE plants and wild-type ZH11.These results suggested that transcription factor OsSPL4 negatively regulated the drought stress response of rice.2.CDS sequence of transcription factor OsSPL4 contains 756 base pairs and encodes 252 amino acids.The N-terminal sequence of the OsSPL4 amino acid has a conserved SBP domain.The promoter region of OsSPL4 gene includes some distinctive cis-acting elements of drought stress response and ABA response.According to GFP fluorescence observation,transcription factor OsSPL4 is located in the nucleus of cell and has the function of transcription-self-activation,and the transcriptionself-activation region focuses on the N-terminus of the sequence.3.Fluorescence quantitative q RT-PCR detection showed that OsSPL4 express in all tissues of rice,with the highest expression level in the fully extended leaves and the roots,which was consistent with the result of highest GUS activity in the leaves and roots of positive OsSPL4-promoter::GUS transgenic plants.In addition,the expression of OsSPL4 was inhibited by ABA treatment and drought stress.4.Based on the results of yeast one hybrid and double luciferase assay,transcription factor OsSPL4 positively dominated the expressions of target genes,OsSPL7,Os STPK(Ser/Thr protein kinase),to regulate the molecular response of rice to the drought stress and ABA treatment.In conclusion,transcription factor OsSPL4 negatively affects the response process of rice to drought stress by positively dominating the expressions of target genes,OsSPL7 and Os STPK,to respond to drought stress.The conclusion obtained by the present study will provide a positive theoretical direction for the performance of molecular-assisted selection breeding of drought-resistant cultivated varieties and the cultivation regulation under the drought condition.