A temperature-responsive gene in sorghum encodes a glycine-rich protein that interacts with calmodulin

Integrative physiological, biochemical, and proteomic analysis of the leaves of two cotton genotypes under heat stress

Cotton (Gossypium hirsutum L.), a crucial global fibre and oil seed crop faces diverse biotic and abiotic stresses. Among these, temperature stress strongly influences its growth, prompting adaptive physiological, biochemical, and molecular changes. In this study, we explored the proteomic changes underscoring the heat stress tolerance in the leaves of two locally developed cotton genotypes, i.e., heat tolerant (GH-Hamaliya Htol) and heat susceptible (CIM-789 Hsus), guided by morpho-physiological and biochemical analysis. These genotypes were sown at two different temperatures, control (35°C) and stress (45°C), in a glasshouse, in a randomized complete block design (RCBD) in three replications. At the flowering stage, a label-free quantitative shotgun proteomics of cotton leaves revealed the differential expression of 701 and 1270 proteins in the tolerant and susceptible genotypes compared to the control, respectively. Physiological and biochemical analysis showed that the heat-tolerant genotype responded uniquely to stress by maintaining the net photosynthetic rate (Pn) (25.2-17.5 μmolCO2m-2S-1), chlorophyll (8.5-7.8mg/g FW), and proline contents (4.9-7.4 μmole/g) compared to control, supported by the upregulation of many proteins involved in several pathways, including photosynthesis, oxidoreductase activity, response to stresses, translation, transporter activities, as well as protein and carbohydrate metabolic processes. In contrast, the distinctive pattern of protein downregulation involved in stress response, oxidoreductase activity, and carbohydrate metabolism was observed in susceptible plants. To the best of our knowledge, this is the first proteomic study on cotton leaves that has identified more than 8000 proteins with an array of differentially expressed proteins responsive to the heat treatment that could serve as potential markers in the breeding programs after further experimentation.

Structural insights to the RRM-domain of the glycine-rich RNA-binding protein from Sorghum bicolor and its role in cold stress tolerance in E. coli

Sorghum bicolor Glycine-rich RNA-binding protein (SbGRBP), exhibit the ability to bind both single-stranded and double-stranded DNA. The expression of SbGRBP is regulated by heat stress, with the protein localizing to the nucleus and cytosol. The present study delves into the structure and ssDNA binding ability of its truncated version (SbGRBP1-119) which lacks glycine rich domain (GR). This protein has the ability to bind ssDNA Using Nuclear Magnetic Resonance (NMR) spectroscopy, we have revealed the secondary structure of SbGRBP1-119, highlighting the typical configuration of GRBPs with four β-sheets and two α-helices. Notably, we found two additional α-helices at the N-terminal region that seem to interact with ssDNA, a novel observation for GRBPs. Key residues crucial for ssDNA binding were identified, suggesting a specific interaction with the oligonucleotide sequence 5'-TTCTGG-3'. Preliminary assays hinted that SbGRBP1-119 might bolster E. coli resilience to cold stress, indicating a potential chaperone-like role under stress conditions. This study sheds light on the structural basis of SbGRBP1-119's interaction with nucleic acids, deepening our understanding about the role of GRBPs' in RNA metabolism and regulation.

Divergence in regulatory mechanisms of GR-RBP genes in different plants under abiotic stress

The IVa subfamily of glycine-rich proteins (GRPs) comprises a group of glycine-rich RNA binding proteins referred to as GR-RBPa here. Previous studies have demonstrated functions of GR-RBPa proteins in regulating stress response in plants. However, the mechanisms responsible for the differential regulatory functions of GR-RBPa proteins in different plant species have not been fully elucidated. In this study, we identified and comprehensively studied a total of 34 GR-RBPa proteins from five plant species. Our analysis revealed that GR-RBPa proteins were further classified into two branches, with proteins in branch I being relatively more conserved than those in branch II. When subjected to identical stresses, these genes exhibited intensive and differential expression regulation in different plant species, corresponding to the enrichment of cis-acting regulatory elements involving in environmental and internal signaling in these genes. Unexpectedly, all GR-RBPa genes in branch I underwent intensive alternative splicing (AS) regulation, while almost all genes in branch II were only constitutively spliced, despite having more introns. This study highlights the complex and divergent regulations of a group of conserved RNA binding proteins in different plants when exposed to identical stress conditions. These species-specific regulations may have implications for stress responses and adaptations in different plant species.

Roles of Plant Glycine-Rich RNA-Binding Proteins in Development and Stress Responses

In recent years, much progress has been made in elucidating the functional roles of plant glycine-rich RNA-binding proteins (GR-RBPs) during development and stress responses. Canonical GR-RBPs contain an RNA recognition motif (RRM) or a cold-shock domain (CSD) at the N-terminus and a glycine-rich domain at the C-terminus, which have been associated with several different RNA processes, such as alternative splicing, mRNA export and RNA editing. However, many aspects of GR-RBP function, the targeting of their RNAs, interacting proteins and the consequences of the RNA target process are not well understood. Here, we discuss recent findings in the field, newly defined roles for GR-RBPs and the actions of GR-RBPs on target RNA metabolism.

Proteomics Analysis of E. angustifolia Seedlings Inoculated with Arbuscular Mycorrhizal Fungi under Salt Stress

To reveal the mechanism of salinity stress alleviation by arbuscular mycorrhizal fungi (AMF), we investigated the growth parameter, soluble sugar, soluble protein, and protein abundance pattern of E. angustifolia seedlings that were cultured under salinity stress (300 mmol/L NaCl) and inoculated by Rhizophagus irregularis (RI). Furthermore, a label-free quantitative proteomics approach was used to reveal the stress-responsive proteins in the leaves of E. angustifolia. The result indicates that the abundance of 75 proteins in the leaves was significantly influenced when E. angustifolia was inoculated with AMF, which were mainly involved in the metabolism, signal transduction, and reactive oxygen species (ROS) scavenging. Furthermore, we identified chorismate mutase, elongation factor mitochondrial, peptidyl-prolyl cis-trans isomerase, calcium-dependent kinase, glutathione S-transferase, glutathione peroxidase, NADH dehydrogenase, alkaline neutral invertase, peroxidase, and other proteins closely related to the salt tolerance process. The proteomic results indicated that E. angustifolia seedlings inoculated with AMF increased the secondary metabolism level of phenylpropane metabolism, enhanced the signal transduction of Ca²⁺ and ROS scavenging ability, promoted the biosynthesis of protein, accelerated the protein folding, and inhibited the degradation of protein under salt stress. Moreover, AMF enhanced the synthesis of ATP and provided sufficient energy for plant cell activity. This study implied that symbiosis of halophytes and AMF has potential as an application for the improvement of saline-alkali soils.

Overexpression of CsCaM3 Improves High Temperature Tolerance in Cucumber

High temperature (HT) stress affects the growth and production of cucumbers, but genetic resources with high heat tolerance are very scarce in this crop. Calmodulin (CaM) has been confirmed to be related to the regulation of HT stress resistance in plants. CsCaM3, a CaM gene, was isolated from cucumber inbred line "02-8." Its expression was characterized in the present study. CsCaM3 transcripts differed among the organs and tissues of cucumber plants and could be induced by HTs or abscisic acid, but not by salicylic acid. CsCaM3 transcripts exhibited subcellular localization to the cytoplasm and nuclei of cells. Overexpression of CsCaM3 in cucumber plants has the potential to improve their heat tolerance and protect against oxidative damage and photosynthesis system damage by regulating the expression of HT-responsive genes in plants, including chlorophyll catabolism-related genes under HT stress. Taken together, our results provide useful insights into stress tolerance in cucumber.