Poster abstracts

Poster number 74 submitted by Caleb Gooden

Characterization of alternative polyadenylation in roots of red clover

Caleb Gooden (Plant and Soil Sciences, University of Kentucky ), Randy Dinkins (Plant and Soil Sciences, University of Kentucky), Arthur Hunt (Plant and Soil Sciences, University of Kentucky )

Root nodulation is a process recognized among legumes in which host roots are infected with a soil bacterium and form nodules that better fix nitrogen from the atmosphere. In agriculture, nodules help to reduce the need for fertilizer and are thus part of sustainable practice. Studies in Medicago truncatula have shown the process of root nodulation to be suppressed by the expression of a regulatory RNA (TAS3). Over-expression of TAS3 and the miR390 pathway with which it interacts resulted in prioritization of lateral root formation over nodulation. Thus, TAS3 is an attractive target for manipulation to improve nitrogen fixation in legumes and enhance their agronomic value.
In Arabidopsis, TAS3a transcripts may end at one of two alternative polyadenylation sites, the choice of which determines whether functional or non-functional TAS3a RNAs are made. We have confirmed through 3’ RACE and bioinformatic analysis that two poly(A) sites are present in the TAS3 region of Trifolium pratense. We also showed that a miR390 site is present in between these two sites through BLAST. We hypothesize that differential use of these sites will determine the production of either lateral roots or nodules, similar to the module shown in Medicago and Arabidopsis, and that use of the proximal site (which produces non-functional TAS3) will be responsible for nodule formation.
Current research focuses on measuring the differential use of these sites through Poly(A) Tag Sequencing (PATseq) and bioinformatic mapping. It is our hypothesis that red clover plants introduced to rhizobia, and therefore exhibiting nodulation, will contain higher numbers of reads at the proximal poly(A) site indicating the expression of the short TAS3 isoform. Conversely, we hypothesize wild-type clover will show higher numbers of reads at the distal poly(A) site indicating expression of full-length, functional TAS3 and production of lateral roots as a result. Control samples of Medicago roots and nodules will be included for comparison.

Keywords: Alternative polyadenylation, red clover, microRNA