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Sudden Death Syndrome (SDS) caused by Fusarium tucumaniae is a significant threat to soybean production in Argentina. This study assessed the susceptibility of SY 3 × 7 and SPS 4 × 4 soybeans cultivars to F. tucumaniae and studied changes in root isoflavone levels after infection. Additionally, the biocontrol potential of plant-growth promoting rhizobacteria (PGPR) against SDS was also examined. Our results demonstrated that the SY 3 × 7 cultivar exhibited higher disease severity and total fresh weight loss than SPS 4 × 4. Both cultivars showed induction of daidzein, glycitein, and genistein in response to infection, with the partially resistant cultivar displaying significantly higher daidzein levels than the susceptible cultivar at 14 days post infection (dpi) (2.74 vs 2.17-fold), declining to a lesser extent at 23 dpi (0.94 vs 0.35-fold, respectively). However, daidzein was not able to inhibit F. tucumaniae growth in in vitro assays probably due to its conversion to an isoflavonoid phytoalexin which would ultimately be an effective fungal inhibitor. Furthermore, the PGPR bacterium Bacillus amyloliquefaciens BNM340 displayed antagonistic activity against F. tucumaniae and reduced SDS symptoms in infected plants. This study sheds light on the varying susceptibility of soybean cultivars to SDS, offers insights into isoflavone responses during infection, and demonstrates the potential of PGPR as a biocontrol strategy for SDS management, providing ways for disease control in soybean production.

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RESUMO

Enzymes from cold-adapted microorganisms are of high interest to industries due to their high activity at low and mild temperatures, which makes them suitable for their use in several processes that either require a supply of exogenous energy or involve the use of heat labile products. In this work, the protease production by the strain Rhodotorula mucilaginosa CBMAI 1528, previously isolated from the Antarctic continent, was optimized, and the purified enzyme analyzed. It was found that protease production was dependent on culture medium composition and growth temperature, being 20 °C and a culture medium containing both glucose and casein peptone (20 and 10 g/L, respectively) the optimal growing conditions in batch as well as in bioreactor. Moreover, mass spectrometry analysis revealed that the enzyme under study has a 100 % sequence identity with the deduced amino acid sequence of a putative aspartic protease from Rhodotorula sp. JG-1b (protein ID: KWU42276.1). This result was confirmed by the decrease of 95 % proteolytic activity by pepstatin A, a specific inhibitor of aspartic proteases. We propose that the enzyme reported here could be Rodothorulapepsin, a protein characterized in 1972 that did not have an associated sequence to date and has been classified as an orphan enzyme.

RESUMO

Antarctica is the coldest, windiest, and driest continent on Earth. In this sense, microorganisms that inhabit Antarctica environments have to be adapted to harsh conditions. Fungal strains affiliated with Ascomycota and Basidiomycota phyla have been recovered from terrestrial and marine Antarctic samples. They have been used for the bioprospecting of molecules, such as enzymes. Many reports have shown that these microorganisms produce cold-adapted enzymes at low or mild temperatures, including hydrolases (e.g. α-amylase, cellulase, chitinase, glucosidase, invertase, lipase, pectinase, phytase, protease, subtilase, tannase, and xylanase) and oxidoreductases (laccase and superoxide dismutase). Most of these enzymes are extracellular and their production in the laboratory has been carried out mainly under submerged culture conditions. Several studies showed that the cold-adapted enzymes exhibit a wide range in optimal pH (1.0-9.0) and temperature (10.0-70.0 °C). A myriad of methods have been applied for cold-adapted enzyme purification, resulting in purification factors and yields ranging from 1.70 to 1568.00-fold and 0.60 to 86.20%, respectively. Additionally, some fungal cold-adapted enzymes have been cloned and expressed in host organisms. Considering the enzyme-producing ability of microorganisms and the properties of cold-adapted enzymes, fungi recovered from Antarctic environments could be a prolific genetic resource for biotechnological processes (industrial and environmental) carried out at low or mild temperatures.

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