Abstract
Universal stress proteins (USPs) are known to be expressed in response to various abiotic stresses in a wide variety of organisms, such as bacteria, archaebacteria, protists, algae, fungi, plants, and animals. However, in plants, biological function of most of the USPs still remains obscure. In the present study, Arabidopsis USP gene (AtUSP) showed induction in response to abscisic acid (ABA) and various abiotic stresses viz. heat, dehydration, salt, osmotic, and cold stresses. Additionally, in silico analysis of AtUSP promoter identified several cis-elements responsive to phytohormones and abiotic stresses such as ABRE, ERE, DRE, and HSE, etc. To functionally validate the AtUSP promoter, the 1115 bp region of promoter was characterized under phytohormone and abiotic stress treatments. Deletion analysis of promoter was carried out by cloning the full length promoter (D0) and its three 5′ deletion derivatives, D1 (964 bp), D2 (660 bp), and D3 (503 bp) upstream of the β-glucuronidase (GUS) reporter gene, which were then stably transformed in Arabidopsis plants. The AtUSP promoter (D0) showed minimal activity under non-stress conditions which was enhanced in response to phytohormone treatments (ABA and ACC) and abiotic stresses such as dehydration, heat, cold, salt, and osmotic stresses. The seedlings harboring D1 and D2 deletion fragments showed constitutive GUS expression even under control condition with increased activity almost under all the treatments. However, D3 seedlings exhibited complete loss of activity under control condition with induction under ACC treatment, dehydration, heat, oxidative, salt, and osmotic stresses. Thus, present study clearly showed that AtUSP promoter is highly inducible by phytohormones and multiple abiotic stresses and it can be exploited as stress inducible promoter to generate multi-stress tolerant crops with minimal effects on their other important traits.
Highlights
During their life cycle, plants have to cope with various abiotic stresses, such as drought, salinity, high or low temperature, oxidative stress, etc
This study showed that AtUSP promoter is multiple stress-responsive and can be used for guiding multiple stress-responsive expression of transgene in transgenic plants
Two week-old seedlings of wild type (WT; ecotype, Col-0) and transgenic Arabidopsis thaliana grown on 1/2 strength Murashige and Skoog (MS; Murashige and Skoog, 1962) medium supplemented with 1% sucrose and 0.8% agar at 22–23◦C with 16/8h photoperiod and light intensity of 100 μmolm−2s−1 were used for AtUSP expression studies and promoter characterization under hormone and abiotic stress treatments, respectively
Summary
Plants have to cope with various abiotic stresses, such as drought, salinity, high or low temperature, oxidative stress, etc. To counter these stresses, plants have evolved various stress tolerance and avoidance mechanisms. Several studies have identified large subset of multiple abiotic stress-responsive genes, which might play important role in crosstalk between various stress signaling pathways (Kilian et al, 2007; Matsui et al, 2008). Nachin et al (2005) showed the role of USP in survival of bacteria when exposed to various stress conditions, such as nutrient starvation and exposure to heat and oxidative stress. The precise function of most of the plant USPs has not been deciphered, so far
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