Comparing Salt and Drought Effects on Gene Expression in a Populus Tree Hybrid

Ismail Asad, * Stephen DiFazio, Dayane Cristina Lima and Danielle Ellis, Department of Biology, West Virginia University, Morgantown, WV 26506

Field (Broad Category): Biology (Biological & Biochemical Sciences) 

Student’s Major: Biology 

High salt concentrations in soil can limit viability of agricultural crop growth by promoting detrimental ionic and osmotic stresses (Munns, 2005). Over 800 million hectares of Earth’s land contain high salinity soil, NaCl being the most abundant (FAO, 2005). Marginal lands with high salinity have reduced economic potential, and hinder land-use efficiency towards fighting world hunger. Drought also jeopardizes crop yield by decreasing plant growth efficiency as well as exacerbating salinity effects (Mi Huh et al, 2010). Genes controlling salt-regulation should follow equivalent expression patterns in salt and drought stressed plants. A hybrid of Populus tremula x Populus alba (female clone 717-1B4) was used in this experiment to compare gene expression differences and similarities between salt- and drought-stressed individuals. Three treatment groups of 5 samples each included salt stress, drought stress, and a control group. Various morphological data were recorded, followed by leaf mRNA extraction and quantitative RT-qPCR. Candidate genes were selected based on a previous salt exposure study, including phosphoribulokinase (PRK) gene, protein phosphatase 2C family gene, KNOTTED-like gene, and an unknown gene involved in chloroplast localization (Lima et al, unpublished). Ubiquitin (UBQ) was used as a housekeeping gene. RT-qPCR results were analyzed using the JMP software to determine normalized gene expression levels. Salt stress reduced basal diameter and shoot dry weight. Drought stress also reduced basal diameter, but additionally stunted new leaf production and leaf expansion. All candidate genes had statistically equivalent expression levels throughout all treatment groups. 

Funding: Henry W. Hurlbutt Memorial Fund - Department of Biology at WVU 

Program/mechanism supporting research/creative efforts: Biology 486 capstone N/A