THE DROUGHT-INDUCED NATIVELY UNFOLDED TRANSCRIPTION FACTOR ASR: IDENTIFICATION OF TARGET GENES THROUGH CHIP-SEQ AND STRUCTURAL FEATURES

MARTINIANO M. RICARDI; DIANA ELENA WETZLER; IUSEM, NORBERTO D.

Foz de Iguazú

Congreso; 11th International Congress of Plant Molecular Biology; 2015

International Plant Molecular Biology (bi-national Argentine-Brazil Organizing Committee)

Abiotic stress accounts for 50% of main crop agricultural losses worldwide. The ASR protein family (a group of the LEA superfamily) has been associated with physiological and adaptive responses to cope with drought. In particular, tomato ASR1 is a natively unfolded protein accumulated upon water stress. It prevents desiccation-induced protein unfolding and binds DNA. Consistently with its previously proposed function as a transcription factor, we identified its DNA-binding sites across the tomato genome by chromatin immunoprecipitation followed by high throughput sequencing (ChIP-seq). From a total 225 enriched regions, 70% localized to gene-containing regions (spanning from 3 kb upstream of the transcription start site to 1 kb downstream of the end of transcription). Aquaporin and cell wall remodeling gene functions were highlighted when performing functional overrepresentation analysis. Moreover, ASR1-overexpressing transgenic tomato plants showed modified expression levels in several transcripts of the identified target genes. Gimmemotif software revealed a well conserved 6-nucleotide motif (TGGGCY) present in all the enriched DNA fragments. Moving forward in the understanding of ASR1 mechanisms of action, we are now attempting to examine its binding to the target motif through in vitro assays by using the recombinant purified protein. We also aim to determine its acquired 3D structure upon DNA binding. For the latter goal, we will rely on low-resolution methods (circular dichroism) as well as high-resolution techniques (X-Ray diffraction of crystals and NMR).