Functional Studies On GmNF-YA7 Regulates Arabidopsis Thaliana In Response To Low Phosphorus Stress And Flowering

NF-Y(Nuclear Factor Y)is an important transcriptional regulatory Factor,which plays an important role in plant and animal growth and stress response.NF-Y is a heterotrimer composed of NF-YA(Nuclear Factor Y,Subunit A),NF-YB and NF-YC.Recent studies have revealed that NF-YA is involved in many physiological processes of plants,including embryonic development,seed development and germination,flower development,root and root nodule development,and plays many important regulatory roles in response to abiotic stress.However,at present,our understanding of the function of NF-YA in response to nutrient stress is still very limited,especially the function of soybean NF-YA in plant growth and development,response to low phosphorus(LP)and nitrogen stress,and response to drought and other stresses.Our previous study found that soybean NF-YA7(Gm NF-YA7)was induced by LP.In this study,the response of Gm NF-YA7 to LP was firstly determined by quantitative real-time PCR,and the subcellular localization of Gm NF-YA7 was analyzed.Then,the effects of heterologous expression of Gm NF-YA7 on the responses of Arabidopsis thaliana to nitrogen and phosphorus stress and drought stress was analyzed.The main results were as follows:(1)The transcript levels of Gm NF-YA7 in soybean leaves at seedling stage was significantly up-regulated under low phosphorus and nitrogen deficiency,but not in roots.In addition,transcripts of Gm NF-YA7 under potassium and iron deficiency in both leaves and roots were not altered.(2)Subcellular localization with fused GFP indicated that Gm NF-YA7 is localizedin the nucleus and plasmembrane.(3)Under high P conditions,over-expressing Gm NF-YA7 in Arabidopsis has no significant influence on primary root length,lateral root number,and lateral root density.However,under low P conditions,the over-expressing Gm NF-YA7 in Arabidopsis resulted in significantly higher emerged lateral roots than wild type(Col-0).Similarly in high N,over-expressing Gm NF-YA7 in Arabidopsis has no influence on the plant primary root length,lateral root number,length of lateral root,and lateral root density,but under low N,over-expressing Gm NF-YA7 significantly increased the number of lateral root,lateral root length,and lateral root density significantly.(4)The number of leaves when the plant bolted 1cm and flowering time of the over-expressing Gm NF-YA7 Arabidopsis were significantly greater than that of the Col-0.At the 25 th day after germination,the plant height of the over-expressing Gm NF-YA7 lines was significantly lower than that of the Col-0,while at the 35 th day after germination,the plant height of the overexpressed materials was not significantly different from that of the Col-0.The number of leaves when the plant bolted 1 cm and flowering time of the over-expressing lines were consistent with that of Col-0 when tsprayed with GA.These results suggest that over-expressing Gm NF-YA7 appear to reduce GA contents in vivo.(5)Compared with the Col-0,the expression levels of At GA2ox2 and At GA2ox3 in the over-expressing Gm NF-YA7 transgenic Arabidopsis were significantly up-regulated.However,both At GA3ox2 and At GA20ox2 were significantly down-regulated in the over-expressing Gm NF-YA7 transgenic plants.Moreover,compared with the Col-0,the expression levels of positive flowering-related genes CO,AP1,SOC1 were significantly down-regulated in over-expressing Gm NF-YA7 Arabidopsis,while the expression levels of the FLC that inhibits flowering were significantly up-regulated in Gm NF-YA7 transgenic lines.(6)Different concentrations of sorbitol and different water potentials of were usedto treat Arabidopsis.The results showed that the primary root,lateral root number and lateral root density of over-expressing Gm NF-YA7 Arabidopsis lines were significantly higher than that of the Col-0 when subjected to sorbitol and polyethylene glycol(8000).These results implied that the over-expressing Gm NF-YA7 enhanced the resistance of Arabidopsis to osmotic stress and drought.In summary,this study determined the expression pattern of Gm NF-YA7,subcellular localization of Gm NF-YA7,and the effects of over-expressing Gm NF-YA7 on the growth and development of Arabidopsis,and the response to low P,low N,and drought stress.It lays a foundation for further intensive studies on the molecular mechanism of soybean NF-YA7 transcription regulatory factor regulating response to low P,low N and drought stress,as well as its action mechanism in regulating the flowering process of plants.