Synthesis of cyanobacterial RNA-binding proteins is regulated by cold- and osmotic-stress

Adaptation to cold stress in bacteria and plants ran be critical for longterm .survival, and represents a significant challenge to agriculture. It is known that plant;, pre-adapted to dehydration or osmotic stress exhibit enhanced cold tolérance. However, little is known about cross-protection between cold and dehydration stresses in bacterial systems. We study mechanisms of desiccation tolerance in the cyanobacterium Anabaena P('( 7120. Anabaena 7120 contains four R.\A binding proteins encoded bv the rbpA.B.C and I) genes. We show that expression of the RbpH protein in Anabaena 7120 is stimulated by cold stress, osmotic stress, salt stress and inatric water slress. High stringency Northern hybridizations with an rbplî probe show that transcripts accumulate to similar high levels after cold shift (30 to 20 C) and osmotic stress with 250 ni.M sucrose. Treatment with 60 m.\I NaCl and overnight desiccation also caused rbpH transcript accuimilation bul to a. significantly lower extent. Western blot.s probed confirm that total Rbp protein levels change in response to both cold and osmotic stresses. Treatments that increase Rbp protein expression also r n h a n ce survival of this si rain during severe cold stress. Cultures of Anabaena 7) ₂0 adapted to osmotic stress prior to cryogenic storage had four-fold higher revival rates that untreated controls. Furthermore, successive pre-treatments with osmotic stress then chilling stress increased viable cell counts after cryogenic storage by iH fold over non-treated controls. The RNA binding proteins in Anabaena 7120 may act as RNA chaparones during both cold and dehydration -tirxM'-. .1- proposed for the (Vp \protein f'oni K.s< herchia roli.