The SALT OVERLY SENSITIVE 2-CONSTITUTIVE TRIPLE RESPONSE1 module coordinates plant growth and salt tolerance in Arabidopsis

Mastering the plant growth symphony: The interplay between calcium sensing machinery and phytohormone signaling during abiotic stress

Climate change introduces a multitude of abiotic stressors, affecting plants' ability to thrive and produce. Abiotic stresses significantly impair plant growth, development, and production, jeopardizing food security. Despite extensive research on individual stress adaptation mechanisms, a critical gap remains in understanding the synergistic role of calcium (Ca2+) signaling and phytohormonal regulation in plant stress responses. Ca2+, a ubiquitous second messenger, plays a pivotal role in stress perception and signal transduction, while phytohormones regulate adaptive physiological and molecular responses. This review aims to bridge the knowledge gap by synthesizing recent advancements in Ca2+-phytohormone interactions and their combined role in enhancing plant resilience to abiotic stress. Hence, understanding these interconnected signaling cascades would pave the path for the development of innovative strategies for enhancing crop stress tolerance, thereby promoting sustainable agriculture in the face of climate change.

From growth to stress: RAF-like kinases as integrators of hormonal signals in plants

RAF-like kinases, members of the mitogen-activated protein kinase kinase kinase (MAPKKK) family, are central integrators of external and internal signals in plant stress responses and growth regulation. These kinases mediate signaling through multiple hormone pathways, including abscisic acid-dependent and -independent pathways, ethylene signaling, and rapid auxin responses. Unlike typical MAPKKKs that function through kinase cascades, RAF-like kinases primarily employ direct phosphorylation of downstream targets and dynamic subcellular localization to mediate specific physiological responses. Here, we review the emerging roles of RAF-like kinases in Arabidopsis thaliana, highlighting their integrative functions in hormone signaling, stress responses, and growth control. The complex interplay between different RAF-like kinase subgroups and their diverse cellular targets underscores the intricate regulatory mechanisms plants have evolved to coordinate environmental responses with development.

The strigolactones-mediated DNA demethylation activates the phosphoinositide pathway in response to salt stress

Salt stress severely affects the growth and development of tomato. Strigolactones (SLs) and DNA methylation have been shown to be involved in the growth and development and response to salt stress in tomato. However, the regulation of SLs on DNA methylation in tomato under salt stress remains unclear. In this study, the interaction between SLs and DNA methylation inhibitors 5-azacytidine (5-azaC) alleviate salt stress damage by increasing the plant height, stem diameter, leaf area, and root length of tomato, as well as enhancing the biosynthesis of chlorophyll, carotenoid and flavonoid. The transcriptome and genome-wide methylation analysis between NaCl and NaCl + GR24 treatment show that plant-pathogen interaction, MAPK signaling pathway, plant hormone signal transduction and phosphatidylinositol signaling system may be means for SLs in response to salt stress. Among, SLs strikingly up-regulate the pivotal genes related to phosphatidylinositol signaling system, and reduce CHG methylation level in promoter and body region of these genes under salt stress, implying that SLs mediated-demethylation may promote gene expression. The determination results of relevant metabolites and gene expression levels in the phosphatidylinositol signaling system suggest that PIP2, DAG, IP3, and PA are raised by co-treatment of SLs and 5-azaC under salt stress relative to NaCl + 5-azaC treatment. The same response pattern is also presented in the SlPLC2, SlNPC1, SlPLD-Z, SlPLD-B, SlDGK1, SlDGK5, SlDGK7 and SlPIP5K9 genes. These results strongly indicate that phosphatidylinositol signaling system response to salt stress is related to the SLs mediated-demethylation, and provide a potential means for defenses salt stress in tomato.

Phosphorylation at serine-260 of Toc33 is essential for chloroplast biogenesis

Chloroplast biogenesis, essential for photosynthesis, depends on the import of nuclear-encoded proteins through the translocon at the outer envelope of chloroplasts (TOC) complexes. Despite its importance, the mechanisms regulating this process remain largely elusive. We identify serine-260 (S260) as a critical phosphorylation site in Toc33, a core TOC component. This phosphorylation stabilizes Toc33 by preventing its ubiquitination and degradation. Constitutive triple response 1 (CTR1), a negative regulator of ethylene signaling, and its paralog RAF-like kinase are involved in phosphorylating Toc33. Disruption of Toc33 phosphorylation impairs its stability and photosynthetic protein import, consequently affecting chloroplast structural integrity and biogenesis. Our findings underscore the essential role of TOC phosphorylation in chloroplast biogenesis and reveal an unexpected regulatory network involving RAF-like kinases in organelle development.

Salinity survival: molecular mechanisms and adaptive strategies in plants

Soil salinity is a significant environmental challenge that threatens plant growth and development, adversely affecting global food crop production. This underscores the critical need to elucidate the molecular mechanisms underlying plant salt tolerance, which has profound implications for agricultural advancement. Recent progress in plant salt tolerance has greatly improved our understanding of the molecular mechanisms of plant responses to salt stress and precision design breeding as an effective strategy for developing new salt-tolerant crop varieties. This review focuses on the model plant species Arabidopsis thaliana and important crops, namely, wheat (Triticum aestivum), maize (Zea mays), and rice (Oryza sativa). It summarizes current knowledge on plant salt tolerance, emphasizing key aspects such as the perception and response to salt stress, Na+ transport, Na+ compartmentalization and clearance, changes in reactive oxygen species induced by salt stress, and regulation of plant stem cell development under salt stress conditions. The review might provide new and valuable information for understanding the molecular mechanisms of plant response and adaptation to salt stress.

ETHYLENE RESPONSE FACTOR6, A Central Regulator of Plant Growth in Response to Stress

ETHYLENE RESPONSE FACTOR6 (ERF6) has emerged as a central player in stress-induced plant growth inhibition. It orchestrates complex pathways that enable plants to acclimate and thrive in challenging environments. In response to various abiotic and biotic stresses, ERF6 is promptly activated through both ethylene-dependent and -independent pathways, and contributes to enhanced stress tolerance mechanisms by activating a broad spectrum of genes at various developmental stages. Despite the crucial role of ERF6, there is currently a lack of published comprehensive insights into its function in plant growth and stress response. In this respect, based on the tight connection between ethylene and ERF6, we review the latest research findings on how ethylene regulates stress responses and the mechanisms involved. In addition, we summarize the trends and advances in ERF6-mediated plant performance under optimal and stressful conditions. Finally, we also highlight key questions and suggest potential paths to unravel the ERF6 regulon in future research.

Revisiting the role of light signaling in plant responses to salt stress

As one of the grave environmental hazards, soil salinization seriously limits crop productivity, growth, and development. When plants are exposed to salt stress, they suffer a sequence of damage mainly caused by osmotic stress, ion toxicity, and subsequently oxidative stress. As sessile organisms, plants have developed many physiological and biochemical strategies to mitigate the impact of salt stress. These strategies include altering root development direction, shortening the life cycle, accelerating dormancy, closing stomata to reduce transpiration, and decreasing biomass. Apart from being a prime energy source, light is an environmental signal that profoundly influences plant growth and development and also participates in plants' response to salt stress. This review summarizes the regulatory network of salt tolerance by light signals in plants, which is vital to further understanding plants' adaptation to high salinity. In addition, the review highlights potential future uses of genetic engineering and light supplement technology by light-emitting diode (LED) to improve crop growth in saline-alkali environments in order to make full use of the vast saline land.

Subcellular dynamics of ethylene signaling drive plant plasticity to growth and stress: Spatiotemporal control of ethylene signaling in Arabidopsis

Volatile compounds, such as nitric oxide and ethylene gas, play a vital role as signaling molecules in organisms. Ethylene is a plant hormone that regulates a wide range of plant growth, development, and responses to stress and is perceived by a family of ethylene receptors that localize in the endoplasmic reticulum. Constitutive Triple Response 1 (CTR1), a Raf-like protein kinase and a key negative regulator for ethylene responses, tethers to the ethylene receptors, but undergoes nuclear translocation upon activation of ethylene signaling. This ER-to-nucleus trafficking transforms CTR1 into a positive regulator for ethylene responses, significantly enhancing stress resilience to drought and salinity. The nuclear trafficking of CTR1 demonstrates that the spatiotemporal control of ethylene signaling is essential for stress adaptation. Understanding the mechanisms governing the spatiotemporal control of ethylene signaling elements is crucial for unraveling the system-level regulatory mechanisms that collectively fine-tune ethylene responses to optimize plant growth, development, and stress adaptation.

Molecular mechanism of salinity and waterlogging tolerance in mangrove Kandelia obovata

Mangrove forests are colloquially referred to as "Earth's kidneys" and serve many important ecological and commercial functions. Salinity and waterlogging stress are the most important abiotic stressors restricting the growth and development of mangroves. Kandelia obovata (K. obovata) is the greatest latitudinally-distributed salt mangrove species in China.Here, morphology and transcriptomics were used to study the response of K. obovata to salt and waterlogging stress. In addition, weighted gene co-expression network analysis of the combined gene expression and phenotypic datasets was used to identify core salinity- and waterlogging-responsive modules. In this study, we observed that both high salinity and waterlogging significantly inhibited growth and development in K. obovata. Notably, growth was negatively correlated with salt concentration and positively correlated with waterlogging duration, and high salinity was significantly more inhibitive than waterlogging. A total of 7, 591 salt-responsive and 228 waterlogging-responsive differentially expressed genes were identified by RNA sequencing. Long-term salt stress was highly correlated with the measured physiological parameters while long-term waterlogging was poorly correlated with these traits. At the same time, 45 salinity-responsive and 16 waterlogging-responsive core genes were identified. All 61 core genes were mainly involved in metabolic and biosynthesis of secondary metabolites pathways. This study provides valuable insight into the molecular mechanisms of salinity and waterlogging tolerance in K. obovata, as well as a useful genetic resource for the improvement of mangrove stress tolerance using molecular breeding techniques.