ROLE OF SUCROGLUCANS IN ABIOTIC STRESS RESPONSE IN A FILAMENTOUS DIAZOTROPHIC CYANOBACTERIUM STRAIN

GIARROCO L. G; GIORGI M. E; SALERNO G. L

Córdoba

Congreso; LX Annual Meeting of the Argentine Society for Biochemistry and Molecular Biology Research (SAIB); 2024

Argentine Society for Biochemistry and Molecular Biology Research (SAIB)

Cyanobacteria are known for their strong adaptability under different environmental conditions. The abiotic stresses,including salinity, drought, and extreme temperatures, primarily affect the physiology and metabolic behavior of thecyanobacteria. In response to stress, the accumulation of compatible solutes (compounds that do not interfere with cellmetabolism) is one of the physiological responses for abiotic stress adaptation. In heterocyst-forming filamentouscyanobacteria, like Nostoc sp. strains, in addition to sucrose we have previously described the synthesis of sucroglucans(series of glucose polymers derived from sucrose) in response to salt stress, and elucidated their structures. In thepresent study, we analyzed the effect of high temperatures on the phenotype of susB-93 and susB-81, two Nostocmutants in all1059 (susB, an orf with high similarity with susA, the sucrose synthase gene). The susB-93 mutant is ableto synthesize sucroglucans under stress but susB-81 has impaired those oligosaccharide synthesis. In parallel, weanalyzed the susA- mutant (which accumulates more sucrose than the wild-type strain), susA+ (which has lessaccumulation of the disaccharide), and susAB- (which has increased sucrose and sucroglucans accumulation). Thesynthesis of both sucrose and sucroglucans was a common response under salt stress. However, with the exception ofsusB-81, cells of the other strains, subjected to high temperatures, accumulated sucroglucans but not sucrose, unlikewhat occurs in cells subjected to salt stress. We also compared the sucroglucan patterns obtained by HPAECPAD, witha Dionex ICS 3000 HPLC system. The differential accumulation of sucrose and sucroglucans indicates the relevantrole of oligosaccharides in heat stress. We therefore propose that sucroglucans, together with their function asosmolytes, may play a role in protecting proteins from aggregation and denaturation, leading to high temperaturetolerance, similar to heat shock proteins. Supported by UNMdP EXA 1142/23, CIC and FIBA.