The Physiological Functions of Universal Stress Proteins and Their Molecular Mechanism to Protect Plants From Environmental Stresses

Abstract

Since the original discovery of a Universal Stress Protein (USP) in Escherichia coli , a number of USPs have been identified from diverse sources including archaea, bacteria, plants, and metazoans. As their name implies, these proteins participate in a broad range of cellular responses to biotic and abiotic stresses. Their physiological functions are associated with ion scavenging, hypoxia responses, cellular mobility, and regulation of cell growth and development. Consistent with their roles in resistance to multiple stresses, USPs show a wide range of structural diversity that results from the diverse range of other functional motifs fused with the USP domain. As well as providing structural diversity, these catalytic motifs are responsible for the diverse biochemical properties of USPs and enable them to act in a number of cellular signaling transducers and metabolic regulators. Despite the importance of USP function in many organisms, the molecular mechanisms by which USPs protect cells and provide stress resistance remain largely unknown. This review addresses the diverse roles of USPs in plants and how the proteins enable plants to resist against multiple stresses in ever-changing environment. Bioinformatic tools used for the collection of a set of USPs from various plant species provide more than 2,100 USPs and their functional diversity in plant physiology. Data from previous studies are used to understand how the biochemical activity of plant USPs modulates biotic and abiotic stress signaling. As USPs interact with the redox protein, thioredoxin, in Arabidopsis and reactive oxygen species (ROS) regulates the activity of USPs, the involvement of USPs in redox-mediated defense signaling is also considered. Finally, this review discusses the biotechnological application of USPs in an agricultural context by considering the development of novel stress-resistant crops through manipulating the expression of USP genes.

The Role of Stress Proteins in Haloarchaea and Their Adaptive Response to Environmental Shifts

“…E. coli harbors six different proteins, USPA, USPC, USPD, USPE, USPF, and USPG, which have shown undefined functions ranging from oxidative stress resistance to motility [ 144 ]. These six E. coli USPs are classified into four subclasses based on the amino acid sequence homology and structural similarity: Class I includes USPA, USPC, and USPD without ATP binding motif; Class II comprises USPF and USPG with ATP binding motif; and USPE has two tandem-repeated USP domains in a polypeptide, designated as E1 and E2, which are grouped into Class III and Class IV, respectively [ 145 ]. Each subclass has its own specific function to deal with a particular environmental stress.…”

“…These results clearly suggest that bacterial USPs have developed distinct physiological functions in order to act in a coordinated way, defending the cell from an external stress. Although their functions have been demonstrated by their structural diversity, the biochemical and molecular mechanism remains largely unknown [ 144 , 145 ]. Focusing on the molecular structures of the diverse bacterial USPs, the USP domain is always present, followed by another catalytic motif in some cases.…”

“…Similar to bacterial USPs, all the USPs identified in plant species contain at least one USP domain and one other catalytic motif. Hence, plant USPs play a distinctive role in specific tissues and developmental stages under diverse stress conditions [ 145 ]. The other catalytic motifs found in plant USPs are the cation exchanger, the C1 motif of Insensitive to Killer toxin3 (IKI3), the HomeoDomain leucine zipper (HDzip), SWI2/snf2 and Mudr (SWIM)-zinc finger, tyrosine kinase, and serine/threonine kinase [ 145 ].…”

QTL mapping and candidate gene identification in rice using a Kalarata-Azucena population under salt stress

“…One example is shown in tobacco wherein unusual expression of SbUSP enhances salt tolerance and increases osmotic stress resistance by removing intracellular reactive oxygen species (ROS). It then recognizes cellular level Na + and activates protein kinases (serine and threonine), which is involved in salt signaling (Chi et al, 2019).…”

Enrichment of Intrinsically Disordered Residues in Ohnologs Facilitate Abiotic Stress Resilience in Brassica Rapa

“…Protein domains entail functional modularity, and it is likely that functional divergence between paralogous pairs exploits this modularity. Experimental evidences reported few domains are assigned for stress tolerance in plants [34] we have assessed protein domains in duplicated pairs by scanning their amino acid sequences. We noticed that duplicated pairs of ASR genes in B. rapa encode signi cantly (Mann-Whitney U test, P = 0.024) higher number of domains than the duplicated pairs in A. thaliana (B.…”