<span style="font-size:11.0pt;font-family: "Times New Roman";mso-fareast-font-family:"Times New Roman";mso-bidi-font-family: Mangal;mso-ansi-language:EN-GB;mso-fareast-language:EN-US;mso-bidi-language: HI" lang="EN-GB">Inducibility of dehydration responsive element (DRE)-based promoter through <i style="mso-bidi-font-style:normal">gusA</i> expression in transgenic tobacco</span>

Abstract

The current study focuses on the pattern of stress-inducibility of a synthetically designed promoter, <i>viz.</i>, 4X DRE (four tandem repeats of dehydration-responsive element), in response to the various stress-inducers like NaCl-mediated salinity, polyethylene glycol (PEG)-mediated water deficit, cold and abscisic acid (ABA). The construct, containing the 4X DRE promoter linked to the reporter gene <i style="mso-bidi-font-style:normal">gusA</i> (that encodes β-glucuronidase, GUS), was introduced in tobacco plants <i>via</i> <i style="mso-bidi-font-style:normal">Agrobacterium</i> <i style="mso-bidi-font-style: normal">tumefaciens</i>-mediated transformation. The T₂ progenies showed the integration of <i style="mso-bidi-font-style:normal">gusA</i>, as verified by polymerase chain reaction (PCR) and DNA Blot hybridization analysis. The <i style="mso-bidi-font-style:normal">gusA</i> induction was noted upon treatment of T₂transgenics with 20% (w/v) PEG for 24 h, while remained undetected even in PEG-treated wild type (WT) plant. The maximum expression was observed in the transgenic plant T₂/3, which also showed induction in <i style="mso-bidi-font-style:normal">gusA</i> expression with other stressors, <i>viz</i>., 200 mM NaCl and cold (4°C). However, PEG-mediated water stress seemed to be the most effective signal for promoter activation, followed by salinity stress and with lesser stimulation by cold. The promoter was activated in a time-dependent manner of stress application, <i>i.e.</i>, greater <i style="mso-bidi-font-style:normal">gusA</i> expression was detected after 24 h of stress as compared to 6 h. ABA application, even at a concentration of 100 <span style="mso-ansi-language:EN-US" lang="EN-US">μM for 24 h, failed to activate reporter gene expression, proving that the promoter is stress-inducible but ABA-independent. Our observation showed the potentiality of 4X DRE for use as a stress-inducible promoter in overexpressing transgene(s) for salinity, drought and cold tolerance.

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