The Functional And Expression Analysis Of A Leucine Zipper Transcription Factor Of Arabidopsis

Transcription factors are one of the groups of proteins that bind to cis-acting DNA regulatory elements using DNA binding domains. They help initiate a program of increased or decreased gene transcription. As such, they are vital for many important cellular processes.Responding to the environmental stimuli such as droughts, high-salinity and hormone, serials of signaling pathways in plants are activated. Transcription factors act downstream of such signaling cascades and bind specific DNA region to control the transcription of specific genes by increasing or preventing the presence of RNA polymerase II. After translation, the newly synthesized genetic products help cells respond to intercellular or environmental signals.Based on the expression characteristics, transcription factors can be of two classes: constitutive and inducible. Although constitutive transcription factors are expressed under both normal and stressful circumstances, they are usually in inert state and of low activity. Under stressful conditions, the conformation or phosphorylation state of these transcription factors will change and get activated. Most of the transcription factors function as the inducible, which are expressed only in the presence of stress, and can be self-regulated by feedback mechanism. We now have a glimpse of how cells can respond to signals, but how cells sense signals, how the signals are tranduced to transcription factors and how transcriptions factors regulate the expression of genes still remain to be uncovered. A thorough understanding of plant signal transduction network of transcription factors in response to stress will require answers to the above questions.The bZIP family of transcription factors is closely related to plant resistance to environmental stress. bZIP proteins gather at ACGT core elements, such as G-box (CACGTG), C-box (CACGTC) and A-box (TACGTA), etc. It has been shown that promoters containing the ACGT core elements are necessary for the ABA-induced gene expression. Among them is G-box, which exists in genes whose expression is induced by ABA, growth hormone, Jasmonic acid and salicylic acid. G-box binding factors (GBF), GBF1, GBF2 and GBF3 from Arabidopsis bZIP family all contain ABA rich region and have similar functions. The three bZIP proteins can form varied heterdimers with distinctive functions.Researches from s. cerevisiae have found that bZIP proteins play a role in yeast anti-oxidation. at3g51960, the transcription factor found in plants, is highly homologous to that of yeast. To examine the in vivo role of at3g51960, the overexpression and silencing vectors were constructed respectively. By using flower dip-dye, the binary expression vectors, pCAMBTA3301: at3g51960 and pCAMBTA3301: at3g51960Promoter, as well as vectors pCAMBTA3301: at3g51960-GFP and pCAMBTA3301: at3g51960cDNA were transformed to Arabidopsis by Tumefaciens. The transgenetic homozygous Arabidopsis strains have been derived after screening. Analysis on these strains reveals that strains overexpressing at3g51960 gene have higher level of stress resistance, implying a role of at3g51960 in plant stress regulation.