THE INTRINSICALLY DISORDERED PROTEIN-PROPERTIES OF THE PLANT PROTEIN ASR1 ARE CLOSELLY RELATED TO ITS FUNCTION AS A DROUGHT STRESS-RESPONSIVE TRANSCRIPTION FACTOR

WETZLER DIANA; RINALDI JIMENA; RICARDI MARTINIANO; BUCCI HERNÁN; IUSEM NORBERTO DANIEL; FUCHS WIGHTMAN, FEDERICO; CARAMELO JULIO JAVIER

Buenos Aires

Congreso; SAIB 2017 (dentro de Reunión Conjunta de Sociedades de Biociencias); 2017

SAIB

Plant species in arid zones are constantly exposed to droughtstress. The ASR (Abscisic, Stress, Ripening) protein family- a subgroupof the late embryogenesis abundant (LEA) superfamily- isinvolved in the water stress response and adaptation to dry environments.Tomato ASR1, as well as other members of this family, ispredicted to be an intrinsically disordered protein (IDP). In this context,we employed biophysical techniques to perform a deep in vitrocharacterization of ASR1 as an IDP protein and showed how both 412 MEDICINA - Volumen 77 - (Supl. I), 2017environmental factors and in vivo targets are related to its folding.We present evidence supporting that ASR1 is an IDP and exhibitsthe plasticity to easily adopt different conformations like the α-helixor polyproline (PII) depending on the surroundings (DG~1 kcal/mol).We also show that environmental changes like low temperaturesand low pH promote ASR1 to be partially folded in a PII conformation.Interestingly, the addition of agents that mimic abiotic stressconditions causes different effects on ASR1 secondary structure.While NaCl diminishes PII content, PEG and glycerol stabilize theα-helix conformation. In addition, we found that Zn2+ binding to ASR1with a defined stoichiometry promotes its folding to α-helix [Kd= (1.3± 0.2) µM]. Extra Zn2+ binding promotes dimerization. Moreover, thebinding of stoichiometric Zn2+ is necessary for binding its specifictarget DNA with a 1:1 stoichiometry [Kd= 216± 10) nM], with a 5-foldpreference over the scrambled sequence oligonucleotide.Furthermore, we designed a FRET reporter to sense ASR1 foldingin vivo. In order to assess its effectiveness, we expressed this proteinsensor in E. coli and tested it under saline and osmotic stress.Overall, this work supports the notion that plasticity of ASR1 is akey feature that facilitates its response to drought stress and theinteraction with its specific targets.