The Roles of Calcineurin B-like Proteins in Plants under Salt Stress

Ameliorative effects of SL on tolerance to salt stress on pepper (Capsicum annuum L.) plants

Salinity is one of the most important problems that threaten agricultural production, especially in arid and semiarid areas. Strigolactones (SLs) are important in providing tolerance to various abiotic stresses in plants. The study was carried out in a hydroponic system to determine the effects of external GR24 (were applied as a foliar spray; 0, 10, and 20 μM) applications at different doses on plant growth and some physiological, biochemical, and gene expression in two pepper genotype (Yalova and Maraş) grown under salt stress (0 and 100 mM NaCl). Plants were harvested and measured 10 days after the NaCl treatments. At the end of the research, it was determined that salt stress negatively affected plant growth in both genotype. Still, SL applications positively affected plant development both under normal and salt stress. While salt stress increased the amount of hydrogen peroxide (H2O2) and malondialdehyde (MDA), SL application caused a decrease in these parameters. Salt stress negatively affected the amount of chlorophyll and photosynthetic properties in both genotype, whereas SL applications mitigated this negative effect. SL applications caused a significant increase in antioxidant enzyme activities under both normal and salt stress conditions. SL content, which decreased with salt stress, increased with exogenous SL application. The content of other plant nutrients except sodium (Na) and chloride (Cl) decreased significantly in pepper seedlings grown under salt stress. External SL applications increased the uptake of these nutrients, especially under salt stress. In addition, the expression levels of CIPK3, CBL2, CCD7, DMAX2, PsbA, PsbB, PsbP1, TIP1;2, TIP5;1, SOS1, SOS2 and HKT2;2 genes were investigated in this study. It was observed that the expression levels of CCD7, DMAX2, SOS1, SOS2, and HKT2;2 genes increased with salinity stress, especially in the Maraş genotype, while SL applications decreased these expression levels. In the study, it was determined that especially exogenous 20 μM SL application could significantly reduce the negative effects of salt stress in pepper.

Tissue-specific chromatin accessibility and transcriptional regulation in maize cold stress response

Maize, a vital crop globally, faces significant yield losses due to its sensitivity to cold stress, especially in temperate regions. Understanding the molecular mechanisms governing maize response to cold stress is crucial for developing strategies to enhance cold tolerance. However, the precise chromatin-level regulatory mechanisms involved remain largely unknown. In this study, we employed DNase-seq and RNA-seq techniques to investigate chromatin accessibility and gene expression changes in maize root, stem, and leaf tissues subjected to cold treatment. We discovered widespread changes in chromatin accessibility and gene expression across these tissues, with strong tissue specificity. Cold stress-induced DNase I hypersensitive sites (coiDHSs) were associated with differentially expressed genes, suggesting a direct link between chromatin accessibility and gene regulation under cold stress. Motif enrichment analysis identified ERF transcription factors (TFs) as central regulators conserved across tissues, with ERF5 emerging as pivotal in the cold response regulatory network. Additionally, TF co-localization analysis highlighted six TF pairs (ERF115-SHN3, ERF9-LEP, ERF7-SHN3, LEP-SHN3, LOB-SHN3, and AS2-LOB) conserved across tissues but showing tissue-specific binding preferences. These findings indicate intricate regulatory networks in maize cold response. Overall, our study provides insights into the chromatin-level regulatory mechanisms underpinning maize adaptive response to cold stress, offering potential targets for enhancing cold tolerance in agricultural contexts.

Genome-wide identification of Rosa roxburghii CML family genes identifies an RrCML13-RrGGP2 interaction involved in calcium-mediated regulation of ascorbate biosynthesis

Calmodulin-like proteins (CMLs) are an essential family of calcium sensors involved in multiple Ca2+-mediated cellular processes in plants. Rosa roxburghii Tratt, known for the abundance of L-ascorbic acid (AsA) in its fruits, is widely distributed in calcium-rich soil of the karst region in southwestern China. The aim of this study was to identify key CMLs that respond to exogenous Ca2+ levels and regulate AsA biosynthesis in R. roxburghii. A genome-wide scan revealed the presence of 41 RrCML genes with 1-4 EF-hand motif (s) unevenly distributed across the 7 chromosomes of R. roxburghii. qRT-PCR analysis revealed that RrCML13, RrCML10, and RrCML36 responded significantly to exogenous Ca2+ treatment, and RrCML13 was positively correlated with GDP-L-galactose phosphorylase encoding gene (RrGGP2) expression and AsA content in the developing fruit. Overexpression of RrCML13 in fruits and roots significantly promoted the transcription of RrGGP2 and the accumulation of AsA, while virus-induced silencing of RrCML13 reduced the transcription of RrGGP2 and the content of AsA. Furthermore, Moreover, the yeast two-hybrid and bimolecular fluorescence complementation (BiFC) analysis confirmed the interaction between RrCML13 and RrGGP2 proteins, indicating that RrCML13 plays a regulatory role in calcium-mediated AsA biosynthesis. This study enhances our understanding of R. roxburghii CMLs and sheds light on the calcium-mediated regulation of AsA biosynthesis.

BnaPLDα1-BnaMPK6 Involved in NaCl-Mediated Overcoming of Self-Incompatibility in Brassica napus L

Self-incompatibility (SI) is an important genetic mechanism exploited by numerous angiosperm species to prevent inbreeding. This mechanism has been widely used in the breeding of SI trilinear hybrids of Brassica napus. The SI responses in these hybrids can be overcome by using a salt (NaCl) solution, which is used for seed propagation in SI lines. However, the mechanism underlying the NaCl-induced breakdown of the SI response in B. napus remains unclear. Here, we investigated the role of two key proteins, BnaPLDα1 and BnaMPK6, in the breakdown of SI induced by NaCl. Pollen grain germination and seed set were reduced in BnaPLDα1 triple mutants following incompatible pollination with NaCl treatment. Conversely, SI responses were partially abolished by overexpression of BnaC05.PLDα1 without salt treatment. Furthermore, we observed that phosphatidic acid (PA) produced by BnaPLDα1 bound to B. napus BnaMPK6. The suppression and enhancement of the NaCl-induced breakdown of the SI response in B. napus were observed in BnaMPK6 quadruple mutants and BnaA05.MPK6 overexpression lines, respectively. Moreover, salt-induced stigmatic reactive oxygen species (ROS) accumulation had a minimal effect on the NaCl-induced breakdown of the SI response. In conclusion, our results demonstrate the essential role of the BnaPLDα1-PA-BnaMPK6 pathway in overcoming the SI response to salt treatment in SI B. napus. Additionally, our study provides new insights into the relationship between SI signaling and salt stress response. SIGNIFICANCE STATEMENT: A new molecular mechanism underlying the breakdown of the NaCl-induced self-incompatibility (SI) response in B. napus has been discovered. It involves the induction of BnaPLDα1 expression by NaCl, followed by the activation of BnaMPK6 through the production of phosphatidic acid (PA) by BnaPLDα1. Ultimately, this pathway leads to the breakdown of SI. The involvement of the BnaPLDα1-PA-BnaMPK6 pathway in overcoming the SI response following NaCl treatment provides new insights into the relationship between SI signalling and the response to salt stress.

The Role of PGPB-Microalgae interaction in Alleviating Salt Stress in Plants

Plant development and yield are severely hampered by climate change. Plants are very prone to a variety of abiotic stressors during growth, making them susceptible to destruction which can reduce the productivity by 20-60%. These stresses generate reactive oxygen species (ROS), which damage lipids, proteins, and nucleic acids. Microalgae and plant growth-promoting bacteria (PGPB) are remarkably effective at reducing the effects of salt stress and promoting plant growth, thereby increasing agricultural yield, and helping ensure global food security. Through a variety of mechanisms, including the production of phytohormones, 1-aminocyclopropane-1-carboxylic acid deaminase, exopolysaccharide, siderophores, hydrogen cyanide, extracellular polymeric substances, volatile organic compounds, and modulation of antioxidants defense machinery under abiotic stresses promote plant growth after inoculation of PGPB and microalgae. These microorganisms also maintain ion homeostasis, offer osmotic balance, stimulate genes that respond to salt and drought, rewire the metabolism, modify the transcription of ion transporter genes, and more. To counteract the negative consequences of salinity stress, this study summarizes the effects of PGPB- microalgae along with a tentative protective mechanism during salinity stress for sustainable agriculture.

Effects of Exogenous Isosteviol on the Physiological Characteristics of Brassica napus Seedlings under Salt Stress

In this paper, the effect of isosteviol on the physiological metabolism of Brassica napus seedlings under salt stress is explored. Brassica napus seeds (Qinyou 2) were used as materials, and the seeds were soaked in different concentrations of isosteviol under salt stress. The fresh weight, dry weight, osmotic substance, absorption and distribution of Na+, K+, Cl-, and the content of reactive oxygen species (ROS) were measured, and these results were combined with the changes shown by Fourier transform infrared spectroscopy (FTIR). The results showed that isosteviol at an appropriate concentration could effectively increase the biomass and soluble protein content of Brassica napus seedlings and reduce the contents of proline, glycine betaine, and ROS in the seedlings. Isosteviol reduces the oxidative damage to Brassica napus seedlings caused by salt stress by regulating the production of osmotic substances and ROS. In addition, after seed soaking in isosteviol, the Na+ content in the shoots of the Brassica napus seedlings was always lower than that in the roots, while the opposite was true for the K+ content. This indicated that under salt stress the Na+ absorbed by the Brassica napus seedlings was mainly accumulated in the roots and that less Na+ was transported to the shoots, while more of the K+ absorbed by the Brassica napus seedlings was retained in the leaves. It is speculated that this may be an important mechanism for Brassica napus seedlings to relieve Na+ toxicity. The spectroscopy analysis showed that, compared with the control group (T1), salt stress increased the absorbance values of carbohydrates, proteins, lipids, nucleic acids, etc., indicating structural damage to the plasma membrane and cell wall. The spectra of the isosteviol seed soaking treatment group were nearly the same as those of the control group (T1). The correlation analysis shows that under salt stress the Brassica napus seedling tissues could absorb large amounts of Na+ and Cl- to induce oxidative stress and inhibit the growth of the plants. After the seed soaking treatment, isosteviol could significantly reduce the absorption of Na+ by the seedling tissues, increase the K+ content, and reduce the salt stress damage to the plant seedlings. Therefore, under salt stress, seed soaking with isosteviol at an appropriate concentration (10-9~10-8 M) can increase the salt resistance of Brassica napus seedlings by regulating their physiological and metabolic functions.