Investigation of the dynamical expression of Nostoc flagelliforme proteome in response to rehydration

To adapt to xeric environments, microorganisms have evolved with the capability of the superior desiccation tolerance and rapid resuscitation after rehydration. Nostoc flagelliforme, a representative terrestrial cyanobacterium that is distributed in west and west-northern parts of China, serves as an ideal model for gaining insight in the physiological recovery mechanism. In this study, LC-MS/MS combined with isobaric chemical labeling technique (iTRAQ) was used to quantify dynamic changes of proteins in N. flagelliforme during the rehydration processes. Approximately 113 proteins were identified to be differentially expressed, with function mainly related to photosynthesis, defense response, biosynthesis, antioxidant system, and energy and carbohydrate metabolism. Among them, protective proteins including high light inducible proteins and antioxidants showed a down regulation trend during the rehydration process, while proteins involved in photosynthesis, biosynthesis and signaling pathways and regulation of gene expression tend to be up-regulated. These results might shed light on molecular mechanism for the N.flagelliforme response to hydration.In this work, iTRAQ-based proteome expression profiling provides a holistic proteomic insight for N. flagelliforme in response to rehydration processes. Proteins involved in defense system could help to limit the damage to a repairable level and maintain cellular physiological integrity in the dried state. In addition, results in this work suggest that changes in expression of light-harvesting complexes phycobilisome is closely related to the switch of photosynthesis apparatus, while only a few proteins in PSI and PSII present significant expression change, which may indicate the integrity of PSI and PSII photosynthetic system.