Staff Scientist/Principal Investigator Pacific Northwest National Laboratory
To date, constitutive overexpression of single genes has been the most common strategy for studying and improving abiotic stress tolerance in plants. However, this strategy has had a relatively limited success due to involvement of multiple pathways in plant adaptation to stress. For that reason, tissue-specific synthetic promoters can be designed to respond specifically to stress conditions. Here, we aimed to develop synthetic promoters comprised of specific stress-responsive cis-elements with appropriate cell-type and element specificity and efficiency. In this work, the responses of Populus tremula x alba to water deficit, salinity, and the combination of two stresses were monitored. To decode the structural and regulatory gene and protein networks that mediate spatiotemporal specialization in leaf and root tissues, a single cell-type specific multi-omics profiling approach was employed, and consequently, unique candidate cell-type specific stress-responsive genes and proteins were identified. We mined poplar transcriptome data for signature promoter motifs that are putatively water deficit- or salt-responsive. De novo motif-detecting algorithms yielded several candidate water deficit- and salt-responsive regulatory elements. Conserved putative motifs were selected and used for constructing fifteen synthetic promoters with heptamerized synthetic motifs, fused to a core promoter sequence downstream to drive a green fluorescent protein (GFP) gene. The generated synthetic promoter-GFP constructs were screened by both protoplasting-transfection and agroinfiltration assays under stress. We found out that 80% of the synthetic promoters induced GFP expression in both transient expression systems. Of special interest were five promoters containing water deficit- and salt stress-induced elements. Introducing these promoters into Arabidopsis showed the induction of promoters SD3-1 and SD6-2 under water deficit stress, and the induction of promoters SS16-1, SS16-2, and SS16-3 under salt stress. This work will contribute to a better understanding of the roles of various poplar specific tissue- and cell type-derived synthetic promoters on the response to abiotic stresses.
Coauthors: Yongil Yang – University of Tennessee;vimal Kumar Balasubramanian – Pacific Northwest National Laboratory (PNNL);Maria Del Mar Rubio Wilhelmi – University of California, Davis;Stephen DiFazio – University of West Virginia;Cumming Jonathan – University of West Virginia;Neal Stewart – University of Tennessee;Eduardo Blumwald – University of California, Davis