Antarctic Moss Multiprotein Bridging Factor 1c Overexpression in Arabidopsis Resulted in Enhanced Tolerance to Salt Stress

Abstract

Polytrichastrum alpinum is one of the moss species that survives extreme conditions in Antarctic. In order to explore the functional benefits of moss genetic resources, P. alpinum multiprotein-bridging factor 1c gene (PaMBF1c) was isolated and characterized. The deduced amino acid sequence of PaMBF1c comprises of a multiprotein-bridging factor (MBF1) domain and a helix-turn-helix (HTH) domain. PaMBF1c expression was induced by different abiotic stresses in P. alpinum, implying its roles in stress responses. We overexpressed PaMBF1c in Arabidopsis and the overexpression phenotypes were analyzed by comparing with the wildtype and/or the Arabidopsis own MBF1c (AtMBF1c) overexpressors. Overexpression of PaMBF1c in Arabidopsis resulted in enhanced tolerance in salt, osmotic, and cold stresses as well as heat stress. More specifically, PaMBF1c overexpressing lines showed better salt tolerance than the wild type, which was not clearly observed in the AtMBF1c overexpressing lines. Thus, these results implicate PaMBF1c evolution under salt-enriched Antarctic soil. RNA-sequencing gene profiling in NaCl treated plants revealed that ten salt-stress inducible genes were already up-regulated in the PaMBF1c overexpressing plants even before NaCl treatment. Gene ontology enrichment analysis with salt up-regulated genes in each line uncovered that the terms of lipid metabolic process, ion transport, cellular amino acid biosynthetic process were significantly enriched in PaMBF1c overexpressor. Additionally, gene enrichment analysis with salt down-regulated genes in each line revealed that the enriched categories in wild type were not significantly overrepresented in the PaMBF1c overexpressing lines. Interestingly, many salt down-regulated ribosome and translation-related genes were not down-regulated in PaMBF1c overexpressing lines under salt stress. These differentially regulated genes by PaMBF1c overexpression could contribute to enhanced tolerance in PaMBF1c overexpressing lines under salt stress.