Function Analysis Of ERF Transcription Factors LeERF2,JERF2 In Responses To Abiotic Stresses

It is the vital step for the response to the stresses of plants to regulate the gene expressions. Hormones and transcription factors play an important role on regulating the gene expressions of plants. ERF transcription factors, which contain a conservative DNA binding domain-ERF domain, and regulate the responses to both biotic and abiotic stresses of plants, such as disease, low temperature, drought, high salinity and wound, belong to a large transcription factors family , which is unique to plants. The ERF transcription factors play a key role on the responses to various stresses of plants. Ethylene (ET) is an important hormone, which can produce a myriad of effects on plant. The early studies showed that ET is important for plants to respond to biotic stress by regulating the expressions of numerous PR genes containing the GCC-box (TAGCCGCC) through ERF transcription factors. In Recent several years, studies supported the fact that ET exerts significant effects on the response to abiotic stress of plants through ERF transcription factors. Our label screened the cDNA expressive library of tomato by yeast one-hybrid system with the GCC-box bait and got two new genes: LeERF2 and JERF2. Studies showed that both of them belong to the ERF transcription factors family. This study is to analyze the functions and regulatory pathway of LeERF2 and JERF2 in the responses to abiotic stresses of plants on the base of the former studies of our label.Our studies illustrated the LeERF2 protein can bind to both GCC-box and DRE/CRT cis-elemengs, but fail to ABRE coupling element (CE1) in the EMSA. We also found that LeERF2 can result in the constitutive expressions of genes containing either GCC-box or DRE/CRT cis-elemengs in their promoters, such as osmotin, PRB-lb, COR15a and RD17 in transgenic tobacco lines. But LeERF2 had no effect on the expression of RD29A or RD29B which containing ABRE element in their promoters. LeERF2 obviously enhanced the tolerance of transgenic tobacco seeds overexpressing the LeERF2 under the salinity and osmotic stresses by treated with NaCl, mannitol, glucose, respectively. LeERF2 transgenic tobacco also demonstrated highly freezing tolerance under the low-temperature treatment. For example, the death rate of wild type is over 80% under the stress of freezing at -6 C for 8 hours, whereas, the transgenic line is only 17%. Another, LeERF2 enhanced the tolerance of salt stress of root of transgenic tobacco lines. From the above results, we believed that LeERF2 enhanced the abiotic tolerance of plants by regulating the expression of genes encoding GCC-box or DRE/CRT element in their promoter.JERF2 also enhanced the tolerance of abiotic stress of transgenic seeds under the stresses of NaCl and mannitol. JERF2 increased the tolerance of transgenic tobacco plants under the stress of NaCl and PEG treatment. Whereas the results of the Northern blotting experiment showed that JERF2 only regulated the expressions of genes osmotin and PRB-lb containing GCC-box cis-elemengs in their promoters in the transgenic tobacco plants, but failed to effect the expressions of COR15a, RD17 RD29A and RD29B containing DRE/CRT or ABRE element in their promoters. Another, we found that transgenic tobacco demonstrated the constitutivephenotype of ethylene for the effect on the production of ET.All above showed that LeERF2, JERF2 perform key function in the response to abiotic stresses of plants and can enhance the tolerance of plants through the different signaling pathways.