Abiotic Stress Resistance, a Novel Moonlighting Function of Ribosomal Protein RPL44 in the Halophilic Fungus Aspergillus glaucus
ABSTRACTRibosomal proteins are highly conserved components of basal cellular organelles, primarily involved in the translation of mRNA leading to protein synthesis. However, certain ribosomal proteins moonlight in the development and differentiation of organisms. In this study, the ribosomal protein L44 (RPL44), associated with salt resistance, was screened from the halophilic fungusAspergillus glaucus(AgRPL44), and its activity was investigated inSaccharomyces cerevisiaeandNicotiana tabacum. Sequence alignment revealed that AgRPL44 is one of the proteins of the large ribosomal subunit 60S. Expression ofAgRPL44was upregulated via treatment with salt, sorbitol, or heavy metals to demonstrate its response to osmotic stress. A homologous sequence from the model fungusMagnaporthe oryzae, MoRPL44, was cloned and compared withAgRPL44in a yeast expression system. The results indicated that yeast cells with overexpressedAgRPL44were more resistant to salt, drought, and heavy metals than were yeast cells expressingMoRPL44at a similar level of stress. WhenAgRPL44was introduced intoM. oryzae, the transformants displayed obviously enhanced tolerance to salt and drought, indicating the potential value ofAgRPL44for genetic applications. To verify the value of its application in plants, tobacco was transformed withAgRPL44, and the results were similar. Taken together, we conclude thatAgRPL44supports abiotic stress resistance and may have value for genetic application.