Identifying differentially expressed proteins in sorghum cell cultures exposed to osmotic stress

Abstract

Drought stress triggers remarkable physiological changes and growth impediments, which significantly diminish plant biomass and crop yield. However, certain plant species show notable resilience, maintaining nearly normal yields under severe water deficits. For example, sorghum is a naturally drought-tolerant crop, which is ideal for studying plant adaptive responses to drought. Here we used sorbitol treatments to simulate drought-induced osmotic stress in sorghum cell suspension cultures and analysed fractions enriched for extracellular matrix proteins using isobaric tags for relative and absolute quantification technology. Sorbitol induced an overall increase in protein secretion, with putative redox proteins, proteases, and glycosyl hydrolases featuring prominently among the responsive proteins. Gene expression analysis of selected candidates revealed regulation at the transcriptional level. There was a notable differential gene expression between drought-tolerant and drought-sensitive sorghum varieties for some of the candidates. This study shows that protein secretion is a major component of the sorghum response to osmotic stress. Additionally, our data provide candidate genes, which may have putative functions in sorghum drought tolerance, and offer a pool of genes that could be developed as potential biomarkers for rapid identification of drought tolerant lines in plant breeding programs.

Establishment and Characterization of Callus and Cell Suspension Cultures of Selected Sorghum bicolor (L.) Moench Varieties: A Resource for Gene Discovery in Plant Stress Biology

“…Studies utilizing Arabidopsis [55] and soybean (Glycine max) [56] cell suspensions have contributed immensely to our understanding of plant signaling molecules [57] and oxidative burst [58] in plant disease response, and proteome changes in response to abiotic stresses [26,59] and pathogen infection [60][61][62], to mention a few. The White sorghum cell culture has been used to study extracellular matrix proteins in response to osmotic stress [19], while the ICSB 338 cell culture has been used in a heat stress study (unpublished data) [63]. Hence, the sorghum cell cultures developed in the current study will provide the wider scientific community with an invaluable resource that could lead to discoveries in biochemical and molecular response networks of this crop towards a range of biotic and abiotic stress factors.…”

“…Total RNA extraction, complementary DNA (cDNA) synthesis and gene expression analysis were carried out as described previously [19], with minor modifications. Briefly, total RNA was extracted from the cell suspension cultures using the Spectrum™ Plant Total RNA kit (Sigma-Aldrich, Dorset, UK) with an on-column DNase digestion step according to the manufacturer's instructions.…”

“…In cell cultures, osmotic stress can be induced using osmotica such as sorbitol and polyethylene glycol (PEG). Sorbitol has been used to induce osmotic stress in sorghum [19], sweet potato (Ipomoea batatas) [20], and tobacco (Nicotiana tabacum L.) [21] cell cultures. PEG has also been used on cell cultures of Stevia rebaudiana [22], sugarcane (Saccharum officinarum L.) [23], scots pine (Pinus sylvestris L.) [24], and Arabidopsis thaliana [25,26].…”

Stress‐adaptive gene discovery by exploiting collective decision‐making of decentralized plant response systems

“…This study confirms that extracellular signalling is quite important and is likely invoked to ensure signal integration across root tissue in the highly heterogeneous rhizosphere to avoid unnecessary activation of drought stress responses. Sorghum cell cultures exposed to osmotic stress activated increased protein secretion, with the level of expression of the encoding genes showing a strong positive correlation with the level of drought‐tolerance achievable across different sorghum lines (Ngara et al ., ). These results suggest that osmotic stress‐induced gene expression and a surge in protein secretion could play a wider role in drought stress‐adaptive responses.…”

Proteomic analysis and interactions network in leaves of mycorrhizal and nonmycorrhizal sorghum plants under water deficit

“…Proteomic analysis of the adaptive response of sorghum to drought and subsequent recovery indicated that proteins related to energy balance, metabolism, and chaperones were the most apparent features to elucidate the differences between the drought-tolerant and sensitive plants (Jedmowski et al, 2014). In sorghum cell suspension subjected to osmotic stress with sorbitol, the secretion of glycosyl-hydrolases/glycosidases, cell wall modifying enzymes, proteases, and redox proteins was increased, suggesting that extracellular matrix proteins had a wide range of functions in adaptive drought-stress responses (Ngara et al, 2018). Arbuscular mycorrhizal (AM) fungi (subphylum Glomeromycotina (Spatafora et al, 2016) establish a biotrophic mutualistic association, called AM symbiosis with more than 80% of angiosperms and gymnosperms based on the current knowledge of Brundett & Tedersoo (2018).…”