Active removal of Na⁺ from the cytosol into the vacuole plays a critical role in salinity tissue tolerance, but another, often neglected component of this trait is Na⁺ retention in vacuoles. This ...retention is based on an efficient control of Na⁺-permeable slow- and fast-vacuolar channels that mediate the back-leak of Na⁺ into cytosol and, if not regulated tightly, could result in a futile cycle. This Tansley insight summarizes our current knowledge of regulation of tonoplast Na⁺-permeable channels and discusses the energy cost of vacuolar Na⁺ sequestration, under different scenarios. We also report on a phylogenetic and bioinformatic analysis of the plant two-pore channel family and the difference in its structure and regulation between halophytes and glycophytes, in the context of salinity tolerance.
This study aimed to reveal the mechanistic basis of the melatonin‐mediated amelioration of salinity stress in plants. Electrophysiological experiments revealed that melatonin decreased salt‐induced ...K+ efflux (a critical determinant of plant salt tolerance) in a dose‐ and time‐dependent manner and reduced sensitivity of the plasma membrane K+‐permeable channels to hydroxyl radicals. These beneficial effects of melatonin were abolished by NADPH oxidase blocker DPI. Transcriptome analyses revealed that melatonin induced 585 (448 up‐ and 137 down‐regulated) and 59 (54 up‐ and 5 down‐regulated) differentially expressed genes (DEGs) in the root tip and mature zone, respectively. The most noticeable changes in the root tip were melatonin‐induced increase in the expression of several DEGs encoding respiratory burst NADPH oxidases (OsRBOHA and OsRBOHF), calcineurin B‐like/calcineurin B‐like‐interacting protein kinase (OsCBL/OsCIPK), and calcium‐dependent protein kinase (OsCDPK) under salt stress. Melatonin also enhanced the expression of potassium transporter genes (OsAKT1, OsHAK1, and OsHAK5). Taken together, these results indicate that melatonin improves salt tolerance in rice by enabling K+ retention in roots, and that the latter process is conferred by melatonin scavenging of hydroxyl radicals and a concurrent OsRBOHF‐dependent ROS signalling required to activate stress‐responsive genes and increase the expression of K+ uptake transporters in the root tip.
Melatonin improves salt tolerance in rice by enabling K+ retention in roots; this process is conferred by melatonin scavenging of hydroxyl radicals and a concurrent OsRBOHF‐dependent ROS signalling required to activate stress‐responsive genes and increasing the expression of K+ uptake transporters, particularly OsHAK5, in the root tip.
Developing drought‐smart, ready‐to‐grow future crops Raza, Ali; Mubarik, Muhammad Salman; Sharif, Rahat ...
The plant genome,
March 2023, 2023-03-00, 20230301, 2023-03-01, Volume:
16, Issue:
1
Journal Article
Peer reviewed
Open access
Breeding crop plants with increased yield potential and improved tolerance to stressful environments is critical for global food security. Drought stress (DS) adversely affects agricultural ...productivity worldwide and is expected to rise in the coming years. Therefore, it is vital to understand the physiological, biochemical, molecular, and ecological mechanisms associated with DS. This review examines recent advances in plant responses to DS to expand our understanding of DS‐associated mechanisms. Suboptimal water sources adversely affect crop growth and yields through physical impairments, physiological disturbances, biochemical modifications, and molecular adjustments. To control the devastating effect of DS in crop plants, it is important to understand its consequences, mechanisms, and the agronomic and genetic basis of DS for sustainable production. In addition to plant responses, we highlight several mitigation options such as omics approaches, transgenics breeding, genome editing, and biochemical to mechanical methods (foliar treatments, seed priming, and conventional agronomic practices). Further, we have also presented the scope of conventional and speed breeding platforms in helping to develop the drought‐smart future crops. In short, we recommend incorporating several approaches, such as multi‐omics, genome editing, speed breeding, and traditional mechanical strategies, to develop drought‐smart cultivars to achieve the ‘zero hunger’ goal.
Core Ideas
Drought stress (DS) significantly affects plant growth and development.
Plants respond and adapt to DS by modifying several physiological, biochemical, and molecular functions.
Advances in different conventional, biochemical, biotechnological, and breeding techniques reveal plant drought tolerance mechanisms.
Data from different approaches can be used with speed breeding for drought‐smart, ready‐to‐grow future crops.
Cuticular wax, the first protective layer of above ground tissues of many plant species, is a key evolutionary innovation in plants. Cuticular wax safeguards the evolution from certain green algae to ...flowering plants and the diversification of plant taxa during the eras of dry and adverse terrestrial living conditions and global climate changes. Cuticular wax plays significant roles in plant abiotic and biotic stress tolerance and has been implicated in defense mechanisms against excessive ultraviolet radiation, high temperature, bacterial and fungal pathogens, insects, high salinity, and low temperature. Drought, a major type of abiotic stress, poses huge threats to global food security and health of terrestrial ecosystem by limiting plant growth and crop productivity. The composition, biochemistry, structure, biosynthesis, and transport of plant cuticular wax have been reviewed extensively. However, the molecular and evolutionary mechanisms of cuticular wax in plants in response to drought stress are still lacking. In this review, we focus on potential mechanisms, from evolutionary, molecular, and physiological aspects, that control cuticular wax and its roles in plant drought tolerance. We also raise key research questions and propose important directions to be resolved in the future, leading to potential applications of cuticular wax for water use efficiency in agricultural and environmental sustainability.
Agriculture is expanding into regions that are affected by salinity. This review considers the energetic costs of salinity tolerance in crop plants and provides a framework for a quantitative ...assessment of costs. Different sources of energy, and modifications of root system architecture that would maximize water vs ion up take are addressed. Energy requirements for transport of salt (NaCl) to leaf vacuoles for osmotic adjustment could be small if there are no substantial leaks back across plasma membrane and tonoplast in root and leaf. The coupling ratio of the H⁺ -ATPase also is a critical component. One proposed leak, that of Na⁺ influx across the plasma membrane through certain aquaporin channels, might be coupled to water flow, thus conserving energy. For the tonoplast, control of two types of cation channels is required for energy efficiency. Transporters controlling the Na⁺ and Cl⁻ concentrations in mitochondria and chloroplasts are largely unknown and could be a major energy cost. The complexity of the system will require a sophisticated modelling approach to identify critical transporters, apoplastic barriers and root structures. This modelling approach will inform experimentation and allow a quantitative assess ment of the energy costs of Na Cl tolerance to guide breeding and engineering of molecular components.
Climate‐resilient crops: Lessons from xerophytes Chen, Xi; Zhao, Chenchen; Yun, Ping ...
The Plant journal : for cell and molecular biology,
March 2024, 2024-Mar, 2024-03-00, 20240301, Volume:
117, Issue:
6
Journal Article
Peer reviewed
Open access
SUMMARY
Developing climate‐resilient crops is critical for future food security and sustainable agriculture under current climate scenarios. Of specific importance are drought and soil salinity. ...Tolerance traits to these stresses are highly complex, and the progress in improving crop tolerance is too slow to cope with the growing demand in food production unless a major paradigm shift in crop breeding occurs. In this work, we combined bioinformatics and physiological approaches to compare some of the key traits that may differentiate between xerophytes (naturally drought‐tolerant plants) and mesophytes (to which the majority of the crops belong). We show that both xerophytes and salt‐tolerant mesophytes have a much larger number of copies in key gene families conferring some of the key traits related to plant osmotic adjustment, abscisic acid (ABA) sensing and signalling, and stomata development. We show that drought and salt‐tolerant species have (i) higher reliance on Na for osmotic adjustment via more diversified and efficient operation of Na+/H+ tonoplast exchangers (NHXs) and vacuolar H+‐ pyrophosphatase (VPPases); (ii) fewer and faster stomata; (iii) intrinsically lower ABA content; (iv) altered structure of pyrabactin resistance/pyrabactin resistance‐like (PYR/PYL) ABA receptors; and (v) higher number of gene copies for protein phosphatase 2C (PP2C) and sucrose non‐fermenting 1 (SNF1)‐related protein kinase 2/open stomata 1 (SnRK2/OST1) ABA signalling components. We also show that the past trends in crop breeding for Na+ exclusion to improve salinity stress tolerance are counterproductive and compromise their drought tolerance. Incorporating these genetic insights into breeding practices could pave the way for more drought‐tolerant and salt‐resistant crops, securing agricultural yields in an era of climate unpredictability.
Significance Statement
This work compare some of the key traits that differentiate between xerophytes (naturally drought‐tolerant plants) and mesophytes (to which majority of the crops belong). Incorporating these genetic insights into breeding practices could pave the way for more drought‐tolerant and salt‐resistant crops, securing agricultural yields in an era of climate unpredictability.
The projected increase of the world’s population, coupled with the shrinking area of arable land required to meet future food demands, is building pressure on Earth’s finite agricultural resources. ...As an alternative to conventional farming methods, crops can be grown in protected environments, such as traditional greenhouses or the more modern plant factories. These are usually more productive and use resources more efficiently than conventional farming and are now receiving much attention—especially in urban and peri-urban areas. Traditionally, protected cropping has been predominantly practised in temperate climates, but interest is rapidly rising in hot, arid areas and humid, tropical regions. However, maintaining suitable climatic conditions inside protected cropping structures in warm climates—where warm is defined as equivalent to climatic conditions that require cooling—is challenging and requires different approaches from those used in temperate conditions. In this paper, we review the benefits of protected cropping in warm climates, as well as the technologies available for maintaining a controlled growing environment in these regions. In addition to providing a summary of active cooling methods, this study summarises photovoltaic (PV)-based shading methods used for passive cooling of greenhouses. Additionally, we also summarise the current humidity-control techniques used in the protected cropping industry and identify future research opportunities in this area. The review includes a list of optimum growing conditions for a range of crop species suited to protected cropping in warm climates.
Summary
Plant K+ uptake typically consists low—affinity mechanisms mediated by Shaker K+ channels (AKT/KAT/KC) and high‐affinity mechanisms regulated by HAK/KUP/KT transporters, which are extensively ...studied. However, the evolutionary and genetic roles of both K+ uptake mechanisms for drought tolerance are not fully explored in crops adapted to dryland agriculture. Here, we employed evolutionary bioinformatics, biotechnological and electrophysiological approaches to determine the role of two important K+ transporters HvAKT2 and HvHAK1 in drought tolerance in barley. HvAKT2 and HvHAK1 were cloned and functionally characterized using barley stripe mosaic virus‐induced gene silencing (BSMV‐VIGS) in drought‐tolerant wild barley XZ5 and agrobacterium‐mediated gene transfer in the barley cultivar Golden Promise. The hallmarks of the K+ selective filters of AKT2 and HAK1 are both found in homologues from strepotophyte algae, and they are evolutionarily conserved in strepotophyte algae and land plants. HvAKT2 and HvHAK1 are both localized to the plasma membrane and have high selectivity to K+ and Rb+ over other tested cations. Overexpression of HvAKT2 and HvHAK1 enhanced K+ uptake and H+ homoeostasis leading to drought tolerance in these transgenic lines. Moreover, HvAKT2‐ and HvHAK1‐overexpressing lines showed distinct response of K+, H+ and Ca2+ fluxes across plasma membrane and production of nitric oxide and hydrogen peroxide in leaves as compared to the wild type and silenced lines. High‐ and low‐affinity K+ uptake mechanisms and their coordination with H+ homoeostasis play essential roles in drought adaptation of wild barley. These findings can potentially facilitate future breeding programs for resilient cereal crops in a changing global climate.
Calcium (Ca
) signaling modulates sodium (Na
) transport in plants; however, the role of the Ca
sensor calmodulin (CaM) in salt tolerance is elusive. We previously identified a salt-responsive ...calmodulin (HvCaM1) in a proteome study of barley (
) roots. Here, we employed bioinformatic, physiological, molecular, and biochemical approaches to determine the role of HvCaM1 in barley salt tolerance. CaM1s are highly conserved in green plants and probably originated from ancestors of green algae of the Chlamydomonadales order.
was mainly expressed in roots and was significantly up-regulated in response to long-term salt stress. Localization analyses revealed that HvCaM1 is an intracellular signaling protein that localizes to the root stele and vascular systems of barley. After treatment with 200 mm NaCl for 4 weeks,
knockdown (RNA interference) lines showed significantly larger biomass but lower Na
concentration, xylem Na
loading, and Na
transportation rates in shoots compared with overexpression lines and wild-type plants. Thus, we propose that
is involved in regulating Na
transport, probably via certain class I high-affinity potassium transporter (HvHKT1;5 and HvHKT1;1)-mediated Na
translocation in roots. Moreover, we demonstrated that HvCaM1 interacted with a CaM-binding transcription activator (HvCAMTA4), which may be a critical factor in the regulation of
in barley. We conclude that HvCaM1 negatively regulates salt tolerance, probably via interaction with HvCAMTA4 to modulate the down-regulation of
and/or the up-regulation of
to reduce shoot Na
accumulation under salt stress in barley.
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