Salt stress induces changes in the proteomic profile of micropropagated sugarcane shoots.

Salt stress is one of the most common stresses in agricultural regions worldwide. In particular, sugarcane is affected by salt stress conditions, and no sugarcane cultivar presently show high productivity accompanied by a tolerance to salt stress. Proteomic analysis allows elucidation of the important pathways involved in responses to various abiotic stresses at the biochemical and molecular levels. Thus, this study aimed to analyse the proteomic effects of salt stress in micropropagated shoots of two sugarcane cultivars (CB38-22 and RB855536) using a label-free proteomic approach. The mass spectrometry proteomics data are available via ProteomeXchange with identifier PXD006075. The RB855536 cultivar is more tolerant to salt stress than CB38-22. A quantitative label-free shotgun proteomic analysis identified 1172 non-redundant proteins, and 1160 of these were observed in both cultivars in the presence or absence of NaCl. Compared with CB38-22, the RB855536 cultivar showed a greater abundance of proteins involved in non-enzymatic antioxidant mechanisms, ion transport, and photosynthesis. Some proteins, such as calcium-dependent protein kinase, photosystem I, phospholipase D, and glyceraldehyde-3-phosphate dehydrogenase, were more abundant in the RB855536 cultivar under salt stress. Our results provide new insights into the response of sugarcane to salt stress, and the changes in the abundance of these proteins might be important for the acquisition of ionic and osmotic homeostasis during exposure to salt stress.

Essential role of K+ uptake permease (Kup) for resistance to sucrose-induced stress in Gluconacetobacter diazotrophicus PAl 5.

Microorganisms are constantly challenged by stressful conditions, such as sugar-rich environments. Such environments can cause an imbalance of biochemical activities and compromise cell multiplication. Gluconacetobacter diazotrophicus PAl 5 is among the most sugar-tolerant bacteria, capable of growing in the presence of up to 876 mM sucrose. However, the molecular mechanisms involved in its response to high sucrose remain unknown. The present work aimed to identify sucrose-induced stress resistance genes in G. diazotrophicus PAl 5. Screening of a Tn5 transposon insertion library identified a mutant that was severely compromised in its resistance to high sucrose concentrations. Molecular characterization revealed that the mutation affected the kupA gene, which encodes a K+ uptake transporter (KupA). Functional complementation of the mutant with the wild type kupA gene recovered the sucrose-induced stress resistance phenotype. High sucrose resistance assay, under different potassium concentrations, revealed that KupA acts as a high-affinity K+ transporter, which is essential for resistance to sucrose-induced stress, when extracellular potassium levels are low. This study is the first to show the essential role of the KupA protein for resistance to sucrose-induced stress in bacteria by acting as a high-affinity potassium transporter in G. diazotrophicus PAl 5.