Morphological Analysis, Protein Profiling and Expression Analysis of Auxin Homeostasis Genes of Roots of Two Contrasting Cultivars of Rice Provide Inputs on Mechanisms Involved in Rice Adaptation towards Salinity Stress

Effect of Claroideoglomus etunicatum and Indole-3-acetic Acid on Growth and Biochemical Properties of Vetiver Grass (Vetiveria zizanioides) Under Salinity Stress

Salinity represents a major environmental factor limiting plant growth and productivity. In order to better understand the effects of arbuscular mycorrhizal fungus Claroideoglomus etunicatum and Indole-3-acetic acid (IAA) on the growth and chemical composition of vetiver grass (Vetiveria zizanioides) under salt stress, a factorial experiment was conducted in a completely randomized design with three replications. The experiment included four NaCl levels (0, 8, 16, and 24 decisiemens per meter (dS/m)) and four levels of treatments (no amendment application, application of IAA, application of C. etunicatum, and interaction of IAA and C. etunicatum) with three replications. The results of the experiment showed that the addition of sodium chloride increased the concentration of proline and the activities of catalase, peroxidase, and superoxide dismutase enzymes. The application of the growth regulator (IAA) and C. etunicatum significantly increased the fresh and dry weight (101%) of shoots, dry weight of roots, and the concentration of macro- and micro-elements in shoots under salinity condition (99.82% phosphorus; 9.79% Iron). The application of mycorrhiza and auxin significantly reduced the concentration of proline and the activities of catalase, peroxidase, and superoxide dismutase enzymes. In general, the addition of IAA and C. etunicatum to roots under salt stress conditions can improve growth and increase the concentration of some nutrients in vetiver shoots.

Genome-Wide Characterization and Expression Profiling of Phytosulfokine Receptor Genes (PSKRs) in Triticum aestivum with Docking Simulations of Their Interactions with Phytosulfokine (PSK): A Bioinformatics Study

Background/Objectives: The phytosulfokine receptor (PSKR) gene family plays a crucial role in regulating plant growth, development, and stress response. Here, the PSKR gene family was characterized in Triticum aestivum L. The study aimed to bridge knowledge gaps and clarify the functional roles of TaPSKRs to create a solid foundation for examining the structure, functions, and regulatory aspects. Methods: The investigation involved genome-wide identification of PSKRs through collection and chromosomal assignment, followed by phylogenetic analysis and gene expression profiling. Additionally, interactions with their interactors were stimulated and analyzed to elucidate their function. Results: The wide-genome inspection of all TaPSKRs led to 25 genes with various homeologs, resulting in 57 TaPSKR members distributed among the A, B, and D subgenomes. Investigating the expression of 61 TaPSKR cDNAs in RNA-seq datasets generated from different growth stages at 14, 21, and 60 days old and diverse tissues such as leaves, shoots, and roots provided further insight into their functional purposes. The expression profile of the TaPSKRs resulted in three key clusters. Gene cluster 1 (GC 1) is partially associated with root growth, suggesting that specific TaPSKRs control root development. The GC 2 cluster targeted genes that show high levels of expression in all tested leaf growth stages and the early developmental stage of the shoots and roots. Furthermore, the GC 3 cluster was composed of genes that are constantly expressed, highlighting their crucial role in regulating various processes during the entire life cycle of wheat. Molecular docking simulations showed that phytosulfokine type α (PSK-α) interacted with all TaPSKRs and had a strong binding affinity with certain TaPSKR proteins, encompassing TaPSKR1A, TaPSKR3B, and TaPSKR13A, that support their involvement in PSK signaling pathways. The crucial arbitration of the affinity may depend on interactions between wheat PSK-α and PSKRs, especially in the LRR domain region. Conclusions: These discoveries deepened our knowledge of the role of the TaPSKR gene family in wheat growth and development, opening up possibilities for further studies to enhance wheat durability and yield via focused innovation approaches.

A rapid and robust colorimetric method for measuring relative abundance of auxins in plant tissues

INTRODUCTION

Auxin estimation in plant tissues is a crucial component of auxin signaling studies. Despite the availability of various high-throughput auxin quantification methods like LC-MS, GC-MS, HPLC, biosensors, and DR5-gus/gfp-based assays, auxin quantification remains troublesome because these techniques are very expensive and technology intensive and they mostly involve elaborate sample preparation or require the development of transgenic plants.

OBJECTIVES

To find a solution to these problems, we made use of an old auxin detection system to quantify microbe derived auxins and modified it to effectively measure auxin levels in rice plants.

MATERIALS AND METHODS

Auxins from different tissues of rice plants, including root samples of seedlings exposed to IAA/TIBA or subjected to different abiotic stresses, were extracted in ethanol. The total auxin level was measured by the presently described colorimetric assay and counterchecked by other auxin estimation methods like LC-MS or gus staining of DR5-gus overexpressing lines.

RESULTS

The presented colorimetric method could measure (1) the auxin levels in different tissues of rice plants, thus identifying the regions of higher auxin abundance, (2) the differential accumulation of auxins in rice roots when auxin or its transport inhibitor was supplied exogenously, and (3) the levels of auxin in roots of rice seedlings subjected to various abiotic stresses. The thus obtained auxin levels correlated well with the auxin levels determined by other methods like LC-MS or gus staining and the expression pattern of auxin biosynthesis pathway genes.

CONCLUSIONS

The auxin estimation method described here is simple, rapid, cost-effective, and sensitive and allows for the efficient detection of relative auxin abundances in plant tissues.

Latest Review Papers in Molecular Plant Sciences 2023

Success in sustaining food security in the face of global climate change depends on the multi-disciplinary efforts of plant science, physics, mathematics, and computer sciences, whereby each discipline contributes specific concepts, information, and tools [...].

The Contribution of Hormonal Changes to the Protective Effect of Endophytic Bacterium Bacillus subtilis on Two Wheat Genotypes with Contrasting Drought Sensitivities under Osmotic Stress

A comparative analysis was conducted to evaluate the effects of seed priming with endophytic bacterium Bacillus subtilis 10-4 (BS) on the hormonal system and cell wall tolerance (lipid peroxidation (LPO), electrolyte leakage (EL), and root lignin deposition) of two Triticum aestivum L. (wheat) varieties with contrasting drought sensitivities (Ekada 70-drought-tolerant (DT); Salavat Yulaev-drought-sensitive (DS)) under normal conditions and 12% polyethylene glycol-6000 (PEG)-induced osmotic stress. The results showed that under normal conditions, the growth stimulation in wheat plants by BS was attributed to changes in the hormonal balance, particularly an increase in endogenous indole-3-acetic acid (IAA) accumulation. However, under stress, a significant hormonal imbalance was observed in wheat seedlings, characterized by a pronounced accumulation of abscisic acid (ABA) and a decrease in the levels of IAA and cytokinins (CK). These effects were reflected in the inhibition of plant growth. BS exhibited a protective effect on stressed plants, as evidenced by a significantly lower amplitude of stress-induced changes in the hormonal system: maintaining the content of IAA at a level close to the control, reducing stress-induced ABA accumulation, and preventing CK depletion. These effects were further reflected in the normalization of growth parameters in dehydrated seedlings, as well as a decrease in leaf chlorophyll degradation, LPO, and EL, along with an increase in lignin deposition in the basal part of the roots in both genotypes. Overall, the findings demonstrate that BS, producing phytohormones, specifically IAA and ABA, had a more pronounced protective effect on DT plants, as evidenced by a smaller amplitude of stress-induced hormonal changes, higher leaf chlorophyll content, root lignin deposition, and lower cell membrane damage (LPO) and permeability (EL) compared to DS plants.

Halotolerant endophytic bacteria alleviate salinity stress in rice (oryza sativa L.) by modulating ion content, endogenous hormones, the antioxidant system and gene expression

Excessive salinity reduces crop production and negatively impacts agriculture worldwide. We previously isolated endophytic bacterial strains from two halophytic species: Artemisia princeps and Chenopodium ficifolium. We used three bacterial isolates: ART-1 (Lysinibacillus fusiformis), ART-10 (Lysinibacillus sphaericus), and CAL-8 (Brevibacterium pityocampae) to alleviate the impact of salinity stress on rice. The impact of 160 mM NaCl salinity on rice was significantly mitigated following inoculation with these bacterial strains, resulting in increased growth and chlorophyll content. Furthermore, OsNHX1, OsAPX1, OsPIN1 and OsCATA expression was increased, but OsSOS expression was decreased. Inductively coupled plasma mass spectrometry (ICP-MS) revealed reduced K+ and Na+ levels in shoots of bacteria-inoculated plants, whereas that of Mg2+ was increased. Bacterial inoculation reduced the content of total flavonoids in rice leaves. Salinized plants inoculated with bacteria showed reduced levels of endogenous salicylic acid (SA) and abscisic acid (ABA) but increased levels of jasmonic acid (JA). In conclusion, the bacterial isolates ART-1, ART-10, and CAL-8 alleviated the adverse effect of salinity on rice growth, which justifies their use as an eco-friendly agricultural practice.

Plant lectins: Classical molecules with emerging roles in stress tolerance

Biotic and abiotic stresses impose adverse effects on plant's development, growth, and production. For the past many years, researchers are trying to understand the stress induced responses in plants and decipher strategies to produce stress tolerant crops. It has been demonstrated that molecular networks encompassing an array of genes and functional proteins play a key role in generating responses to combat different stresses. Newly, there has been a resurgence of interest to explore the role of lectins in modulating various biological responses in plants. Lectins are naturally occurring proteins that form reversible linkages with their respective glycoconjugates. To date, several plant lectins have been recognized and functionally characterized. However, their involvement in stress tolerance is yet to be comprehensively analyzed in greater detail. The availability of biological resources, modern experimental tools, and assay systems has provided a fresh impetus for plant lectin research. Against this backdrop, the present review provides background information on plant lectins and recent knowledge on their crosstalks with other regulatory mechanisms, which play a remarkable role in plant stress amelioration. It also highlights their versatile role and suggests that adding more information to this under-explored area will usher in a new era of crop improvement.

A genome-wide association study identifies novel players in Na and Fe homeostasis in Arabidopsis thaliana under alkaline-salinity stress

In nature, multiple stress factors occur simultaneously. The screening of natural diversity panels and subsequent Genome-Wide Association Studies (GWAS) is a powerful approach to identify genetic components of various stress responses. Here, the nutritional status variation of a set of 270 natural accessions of Arabidopsis thaliana grown on a natural saline-carbonated soil is evaluated. We report significant natural variation on leaf Na (LNa) and Fe (LFe) concentrations in the studied accessions. Allelic variation in the NINJA and YUC8 genes is associated with LNa diversity, and variation in the ALA3 is associated with LFe diversity. The allelic variation detected in these three genes leads to changes in their mRNA expression and correlates with plant differential growth performance when plants are exposed to alkaline salinity treatment under hydroponic conditions. We propose that YUC8 and NINJA expression patters regulate auxin and jasmonic signaling pathways affecting plant tolerance to alkaline salinity. Finally, we describe an impairment in growth and leaf Fe acquisition associated with differences in root expression of ALA3, encoding a phospholipid translocase active in plasma membrane and the trans Golgi network which directly interacts with proteins essential for the trafficking of PIN auxin transporters, reinforcing the role of phytohormonal processes in regulating ion homeostasis under alkaline salinity.

Proteomic Approaches to Uncover Salt Stress Response Mechanisms in Crops

Salt stress is an unfavorable outcome of global climate change, adversely affecting crop growth and yield. It is the second-biggest abiotic factor damaging the morphological, physio-biochemical, and molecular processes during seed germination and plant development. Salt responses include modulation of hormonal biosynthesis, ionic homeostasis, the antioxidant defense system, and osmoprotectants to mitigate salt stress. Plants trigger salt-responsive genes, proteins, and metabolites to cope with the damaging effects of a high salt concentration. Enhancing salt tolerance among crop plants is direly needed for sustainable global agriculture. Novel protein markers, which are used for crop improvement against salt stress, are identified using proteomic techniques. As compared to single-technique approaches, the integration of genomic tools and exogenously applied chemicals offers great potential in addressing salt-stress-induced challenges. The interplay of salt-responsive proteins and genes is the missing key of salt tolerance. The development of salt-tolerant crop varieties can be achieved by integrated approaches encompassing proteomics, metabolomics, genomics, and genome-editing tools. In this review, the current information about the morphological, physiological, and molecular mechanisms of salt response/tolerance in crops is summarized. The significance of proteomic approaches to improve salt tolerance in various crops is highlighted, and an integrated omics approach to achieve global food security is discussed. Novel proteins that respond to salt stress are potential candidates for future breeding of salt tolerance.

IAA Plays an Important Role in Alkaline Stress Tolerance by Modulating Root Development and ROS Detoxifying Systems in Rice Plants

Auxin regulates plant growth and development, as well as helps plants to survive abiotic stresses, but the effects of auxin on the growth of alkaline-stressed rice and the underlying molecular and physiological mechanisms remain unknown. Through exogenous application of IAA/TIBA, this study explored the physiological and molecular mechanisms of alkaline stress tolerance enhancement using two rice genotypes. Alkaline stress was observed to damage the plant growth, while exogenous application of IAA mitigates the alkaline-stress-induce inhibition of plant growth. After application of exogenous IAA to alkaline-stressed rice, dry shoot biomass, foliar chlorophyll content, photosynthetic rate in the two rice genotypes increased by 12.6-15.6%, 11.7-40.3%, 51.4-106.6%, respectively. The adventitious root number, root surface area, total root length and dry root biomass in the two rice genotypes increased by 29.3-33.3%, 26.4-27.2%, 42.5-35.5% and 12.8-33.1%, respectively. The accumulation of H₂O₂, MAD were significantly decreased with the application of IAA. The activities of CAT, POD, and SOD in rice plants were significantly increased by exogenous application of IAA. The expression levels of genes controlling IAA biosynthesis and transport were significantly increased, while there were no significant effects on the gene expression that controlled IAA catabolism. These results showed that exogenous application of IAA could mitigate the alkaline-stress-induced inhibition of plant growth by regulating the reactive oxygen species scavenging system, root development and expression of gene involved in IAA biosynthesis, transport and catabolism. These results provide a new direction and empirical basis for improving crop alkaline tolerance with exogenous application of IAA.

Comparative Transcriptome Analysis Unravels Defense Pathways of Fraxinus velutina Torr Against Salt Stress

Fraxinus velutina Torr with high salt tolerance has been widely grown in saline lands in the Yellow River Delta, China. However, the salt-tolerant mechanisms of F. velutina remain largely elusive. Here, we identified two contrasting cutting clones of F. velutina, R7 (salt-tolerant), and S4 (salt-sensitive) by measuring chlorophyll fluorescence characteristics (Fv/Fm ratio) in the excised leaves and physiological indexes in roots or leaves under salt treatment. To further explore the salt resistance mechanisms, we compared the transcriptomes of R7 and S4 from leaf and root tissues exposed to salt stress. The results showed that when the excised leaves of S4 and R7 were, respectively, exposed to 250 mM NaCl for 48 h, Fv/Fm ratio decreased significantly in S4 compared with R7, confirming that R7 is more tolerant to salt stress. Comparative transcriptome analysis showed that salt stress induced the significant upregulation of stress-responsive genes in R7, making important contributions to the high salt tolerance. Specifically, in the R7 leaves, salt stress markedly upregulated key genes involved in plant hormone signaling and mitogen-activated protein kinase signaling pathways; in the R7 roots, salt stress induced the upregulation of main genes involved in proline biosynthesis and starch and sucrose metabolism. In addition, 12 genes encoding antioxidant enzyme peroxidase were all significantly upregulated in both leaves and roots. Collectively, our findings revealed the crucial defense pathways underlying high salt tolerance of R7 through significant upregulation of some key genes involving metabolism and hub signaling pathways, thus providing novel insights into salt-tolerant F. velutina breeding.