As sessile organisms, plants must cope with abiotic stress such as soil salinity, drought, and extreme temperatures. Core stress-signaling pathways involve protein kinases related to the yeast SNF1 ...and mammalian AMPK, suggesting that stress signaling in plants evolved from energy sensing. Stress signaling regulates proteins critical for ion and water transport and for metabolic and gene-expression reprogramming to bring about ionic and water homeostasis and cellular stability under stress conditions. Understanding stress signaling and responses will increase our ability to improve stress resistance in crops to achieve agricultural sustainability and food security for a growing world population.
Understanding the core set of pathways that allow plants to cope with abiotic stresses such as salinity, drought, and extreme temperatures can allow us to improve crop sustainability and food security for a growing world population.
DNA methylation is a conserved epigenetic modification that is important for gene regulation and genome stability. Aberrant patterns of DNA methylation can lead to plant developmental abnormalities. ...A specific DNA methylation state is an outcome of dynamic regulation by de novo methylation, maintenance of methylation and active demethylation, which are catalysed by various enzymes that are targeted by distinct regulatory pathways. In this Review, we discuss DNA methylation in plants, including methylating and demethylating enzymes and regulatory factors, and the coordination of methylation and demethylation activities by a so-called methylstat mechanism; the functions of DNA methylation in regulating transposon silencing, gene expression and chromosome interactions; the roles of DNA methylation in plant development; and the involvement of DNA methylation in plant responses to biotic and abiotic stress conditions.
Plants cannot move, so they must endure abiotic stresses such as drought, salinity and extreme temperatures. These stressors greatly limit the distribution of plants, alter their growth and ...development, and reduce crop productivity. Recent progress in our understanding of the molecular mechanisms underlying the responses of plants to abiotic stresses emphasizes their multilevel nature; multiple processes are involved, including sensing, signalling, transcription, transcript processing, translation and post-translational protein modifications. This improved knowledge can be used to boost crop productivity and agricultural sustainability through genetic, chemical and microbial approaches.
Defense against stress and active suppression of growth are two complementary strategies by which plants respond to adverse environments. Although beneficial for plant survival, active growth ...inhibition is often undesirable for crop productivity. Compared with the knowledge on how plants defend against stress-caused cellular impairment, much less is known about how stress signaling regulates plant growth and vice versa. Here, we review recent progress in this area and discuss recent studies suggesting that reciprocal regulation between stress-response and growth-control pathways occurs at multiple levels. Understanding this regulatory network will be critical for resetting the balance between stress resistance and growth in order to engineer stress-resistant and high-yielding crops.
Defense against stress and suppression of growth are complementary strategies by which plants respond to adverse environments. Although beneficial for plant survival, active growth inhibition is often undesirable for crop productivity. Zhang et al. review recent progress in this area and discuss the reciprocal regulation between stress-response and growth-control pathways.
Summary
Base editing is a novel genome editing strategy that enables irreversible base conversion at target loci without the need for double stranded break induction or homology‐directed repair. ...Here, we developed new adenine and cytosine base editors with engineered SpCas9 and SaCas9 variants that substantially expand the targetable sites in the rice genome. These new base editors can edit endogenous genes in the rice genome with various efficiencies. Moreover, we show that adenine and cytosine base editing can be simultaneously executed in rice. The new base editors described here will be useful in rice functional genomics research and will advance precision molecular breeding in crops.
To identify novel cancer therapies, the tumor microenvironment (TME) has received a lot of attention in recent years in particular with the advent of clinical successes achieved by targeting immune ...checkpoint inhibitors (ICIs). The TME consists of multiple cell types that are embedded in the extracellular matrix (ECM), including immune cells, endothelial cells and cancer associated fibroblasts (CAFs), which communicate with cancer cells and each other during tumor progression. CAFs are a dominant and heterogeneous cell type within the TME with a pivotal role in controlling cancer cell invasion and metastasis, immune evasion, angiogenesis and chemotherapy resistance. CAFs mediate their effects in part by remodeling the ECM and by secreting soluble factors and extracellular vesicles. Exosomes are a subtype of extracellular vesicles (EVs), which contain various biomolecules such as nucleic acids, lipids, and proteins. The biomolecules in exosomes can be transmitted from one to another cell, and thereby affect the behavior of the receiving cell. As exosomes are also present in circulation, their contents can also be explored as biomarkers for the diagnosis and prognosis of cancer patients. In this review, we concentrate on the role of CAFs-derived exosomes in the communication between CAFs and cancer cells and other cells of the TME. First, we introduce the multiple roles of CAFs in tumorigenesis. Thereafter, we discuss the ways CAFs communicate with cancer cells and interplay with other cells of the TME, and focus in particular on the role of exosomes. Then, we elaborate on the mechanisms by which CAFs-derived exosomes contribute to cancer progression, as well as and the clinical impact of exosomes. We conclude by discussing aspects of exosomes that deserve further investigation, including emerging insights into making treatment with immune checkpoint inhibitor blockade more efficient.
Stomata, the pores formed by a pair of guard cells, are the main gateways for water transpiration and photosynthetic CO2 exchange, as well as pathogen invasion in land plants. Guard cell movement is ...regulated by a combination of environmental factors, including water status, light, CO2 levels and pathogen attack, as well as endogenous signals, such as abscisic acid and apoplastic reactive oxygen species (ROS). Under abiotic and biotic stress conditions, extracellular ROS are mainly produced by plasma membrane‐localized NADPH oxidases, whereas intracellular ROS are produced in multiple organelles. These ROS form a sophisticated cellular signaling network, with the accumulation of apoplastic ROS an early hallmark of stomatal movement. Here, we review recent progress in understanding the molecular mechanisms of the ROS signaling network, primarily during drought stress and pathogen attack. We summarize the roles of apoplastic ROS in regulating stomatal movement, ABA and CO2 signaling, and immunity responses. Finally, we discuss ROS accumulation and communication between organelles and cells. This information provides a conceptual framework for understanding how ROS signaling is integrated with various signaling pathways during plant responses to abiotic and biotic stress stimuli.
Stomata are the main gateways for water transpiration and photosynthetic CO2 exchange, as well as pathogen invasion in land plants. Stomatal movement is regulated by a combination of environmental factors including water status, light, CO2 levels and pathogen attack, as well as abscisic acid and apoplastic reactive oxygen species (ROS).
Domestication has resulted in reduced salt tolerance in tomato. To identify the genetic components causing this deficiency, we performed a genome‐wide association study (GWAS) for root Na+/K+ ratio ...in a population consisting of 369 tomato accessions with large natural variations. The most significant variations associated with root Na+/K+ ratio were identified within the gene SlHAK20 encoding a member of the clade IV HAK/KUP/KT transporters. We further found that SlHAK20 transports Na+ and K+ and regulates Na+ and K+ homeostasis under salt stress conditions. A variation in the coding sequence of SlHAK20 was found to be the causative variant associated with Na+/K+ ratio and confer salt tolerance in tomato. Knockout mutations in tomato SlHAK20 and the rice homologous genes resulted in hypersensitivity to salt stress. Together, our study uncovered a previously unknown molecular mechanism of salt tolerance responsible for the deficiency in salt tolerance in cultivated tomato varieties. Our findings provide critical information for molecular breeding to improve salt tolerance in tomato and other crops.
Synopsis
Selection of large fruits in domesticated tomato is linked to a reduction in salt tolerance. This study links domestication‐associated variation in the Na+/K+ transporter‐coding gene SlHAK20 to reduced salt tolerance in cultivated plants.
Root Na+/K+ ratios show a strong positive correlation with fruit weight during tomato domestication.
A variation in SlHAK20 is associated with Na+/K+ ratio modulation in tomato roots under salt stress conditions.
The SlHAK20Hap1 haplotype is more effective than SlHAK20Hap2 in conferring Na+ homeostasis and salt tolerance.
The role of SlHAK20 in regulation of salt tolerance is conserved in rice.
A genome‐wide association study links reduced sodium ion uptake by SlHAK20 transporter to diminished salt tolerance and increased fruit weight in cultivated tomato.
Magnetization switching by spin-orbit torque (SOT) via spin Hall effect represents as a competitive alternative to that by spin-transfer torque (STT) used for magnetoresistive random access memory ...(MRAM), as it doesn't require high-density current to go through the tunnel junction. For perpendicular MRAM, however, SOT driven switching of the free layer requires an external in-plane field, which poses limitation for viability in practical applications. Here we demonstrate field-free magnetization switching of a perpendicular magnet by utilizing an Iridium (Ir) layer. The Ir layer not only provides SOTs via spin Hall effect, but also induce interlayer exchange coupling with an in-plane magnetic layer that eliminates the need for the external field. Such dual functions of the Ir layer allows future build-up of magnetoresistive stacks for memory and logic applications. Experimental observations show that the SOT driven field-free magnetization reversal is characterized as domain nucleation and expansion. Micromagnetic modeling is carried out to provide in-depth understanding of the perpendicular magnetization reversal process in the presence of an in-plane exchange coupling field.
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