Strigolactones interact with other phytohormones to modulate plant root growth and development

Strigolactones(SLs),which are biosynthesized mainly in roots,modulate various aspects of plant growth and development.Here,we review recent research on the role of SLs and their cross-regulation with auxin,cytokinin,and ethylene in the modulation of root growth and development.Under nutrientsufficient conditions,SLs regulate the elongation of primary roots and inhibit adventitious root formation in eudicot plants.SLs promote the elongation of seminal roots and increase the number of adventitious roots in grass plants in the short term,while inhibiting lateral root development in both grass and eudicot plants.The effects of SLs on the elongation of root hairs are variable and depend on plant species,growth conditions,and SL concentration.Nitrogen or phosphate deficiency induces the accumulation of endogenous SLs,modulates root growth and development.Genetic analyses indicate cross-regulation of SLs with auxin,cytokinin,and ethylene in regulation of root growth and development.We discuss the implications of these studies and consider their potential for exploiting the components of SL signaling for the design of crop plants with more efficient soil-resource utilization.

Integrative multi-omics approaches reveal that Asian cultivated rice domestication influences its symbiotic relationship with arbuscular mycorrhizal fungi

Potential changes in the symbiotic relationship between rice(Oryza sativa)and microorganisms have occurred during the domestication of Asian cultivated rice(O.sativa)from common wild rice(Oryza rufipogon)and in response to global climate change,along with evolving adaptations to the environment.The potential genes may express differently or dominate the symbiotic relationships between arbuscular mycorrhizal fungi(AMF)and plants,which may be beneficial to rice breeding.To date,research on this important topic has been limited.In this study,we aimed to examine the symbiotic relationships of Asian common wild and cultivated rice species with AMF.By conducting a comparative metagenomic analysis of the rhizospheres of wild and cultivated rice species,we identified differences in Rhizophagus intraradices-related genes associated with wild and cultivated rice,as well as functional genes of AMF.Furthermore,we obtained root-related genes associated with AMF from transcriptome data of rice roots.Our results collectively suggest that R.intraradices-related genes in the rhizosphere of wild rice may be more conducive to its colonization.Additionally,bacteria from the Nitrosomonadaceae and Nitrospiraceae families identified in the rhizosphere of wild rice exhibited positive correlations with R.intraradices-related genes with protein identifiers 1480749 and1871253,which may indicate that nitrobacteria can enhance the functions of R.intraradices in association with wild rice.Next,in a case study using comparative transcriptome analysis of root samples obtained from R.intraradices-inoculated wild and cultivated rice plants,we found significantly higher expression levels of the strigolactone pathway-related genes DWARF3(D3)and DWARF14(D14)in R.intraradices-inoculated common wild rice than in R.intraradices-inoculated cultivated rice.This study provides a theoretical basis for identifying the effects of domestication on mycorrhizal symbiosis-related genes,which could be promoted in wild rice in the future.

Carrageenans as biostimulants and bio-elicitors:plant growth and defense responses

In the context of climate change,the need to ensure food security and safety has taken center stage.Chemical fertilizers and pesticides are traditionally used to achieve higher plant productivity and improved plant protection from biotic stresses.However,the widespread use of fertilizers and pesticides has led to significant risks to human health and the environment,which are further compounded by the emissions of greenhouse gases during fertilizer and pesticide production and application,contributing to global warming and climate change.The naturally occurring sulfated linear polysaccharides obtained from edible red seaweeds(Rhodophyta),carrageenans,could offer climate-friendly substitutes for these inputs due to their bi-functional activities.Carrageenans and their derivatives,known as oligo-carrageenans,facilitate plant growth through a multitude of metabolic courses,including chlorophyll metabolism,carbon fixation,photosynthesis,protein synthesis,secondary metabolite generation,and detoxification of reactive oxygen species.In parallel,these compounds suppress pathogens by their direct antimicrobial activities and/or improve plant resilience against pathogens by modulating biochemical changes via salicylate(SA)and/or jasmonate(JA)and ethylene(ET)signaling pathways,resulting in increased production of secondary metabolites,defense-related proteins,and antioxidants.The present review summarizes the usage of carrageenans for increasing plant development and defense responses to pathogenic challenges under climate change.In addition,the current state of knowledge regarding molecular mechanisms and metabolic alterations in plants during carrageenan-stimulated plant growth and plant disease defense responses has been discussed.This evaluation will highlight the potential use of these new biostimulants in increasing agricultural productivity under climate change.

Acetic acid:a cheap but chief metabolic regulator for abiotic stress tolerance in plants

As sessile organisms,plants constantly face a variety of abiotic stresses,such as drought,salinity,and metal/metalloid toxicity,all of which possess significant threats to plant growth and yield potential.Improving plant resilience to such abiotic stresses bears paramount importance in practicing sustainable agriculture worldwide.Acetic acid/acetate has been recognized as an important metabolite with multifaceted roles in regulating plant adaptation to diverse abiotic stresses.Recent studies have elucidated that acetic acid can potentiate plants’inherent mechanisms to withstand the adverse effects of abiotic stresses through the regulation of lipid metabolism,hormone signaling,epigenetic changes,and physiological defense mechanisms.Numerous studies also underpin the potential use of acetic acid in boosting crop production under unfavorable environmental conditions.This review provides a comprehensive update on the understanding of how acetic acid regulates plant photosynthesis,acts as an antitranspirant,detoxifies reactive oxygen species to alleviate oxidative stress,interacts with phytohormones to regulate physiological processes,and improves soil fertility and microbial diversity,with a specific focus on drought,salinity,and metal toxicity.We also highlight the eco-friendly and economic potential of acetic acid that may attract farmers from developing countries to harness the benefits of acetic acid application for boosting abiotic stress resistance in crops.Given that acetic acid is a widely accessible,inexpensive,and eco-friendly compound,the revelation of acetic acid-mediated regulatory pathways and its crosstalk with other signaling molecules will have significant importance in developing a sustainable strategy for mitigating abiotic stresses in crops.

Regulation of Photosynthesis during Abiotic Stress-Induced Photoinhibition

Plants as sessile organisms are continuously exposed to abiotic stress conditions that impose numerous detrimental effects and cause tremendous loss of yield. Abiotic stresses, including high sunlight, confer serious damage on the photosynthetic machinery of plants. Photosystem II （PSII） is one of the most susceptible components of the photosynthetic machinery that bears the brunt of abiotic stress. In addition to the generation of reactive oxygen species （ROS） by abiotic stress, ROS can also result from the absorption of excessive sunlight by the light-harvesting complex. ROS can damage the photosynthetic apparatus, particularly PSII, resulting in photoinhibition due to an imbalance in the photosynthetic redox signaling pathways and the inhibition of PSII repair. Designing plants with improved abiotic stress tolerance will require a comprehensive understanding of ROS signaling and the regulatory functions of various components, including protein kinases, transcription factors, and phytohormones, in the responses of photosynthetic machinery to abiotic stress. Bioenergetics approaches, such as chlorophyll a transient kinetics analysis, have facilitated our understanding of plant vitality and the assessment of PSII efficiency under adverse environmental conditions. This review discusses the current understanding and indicates potential areas of further studies on the regulation of the photosynthetic machinery under abiotic stress.

Biochar potentially enhances maize tolerance to arsenic toxicity by improving physiological and biochemical responses to excessive arsenate

Metalloid pollution,including arsenic poisoning,is a serious environmental issue,plaguing plant productivity and quality of life worldwide.Biochar,a carbon-rich material,has been known to alleviate the negative effects of environmental pollutants on plants.However,the specific role of biochar in mitigating arsenic stress in maize remains relatively unexplored.Here,we elucidated the functions of biochar in improving maize growth under the elevated level of sodium arsenate(Na_(2)AsO_(4),AsV).Maize plants were grown in pot-soils amended with two doses of biochar(2.5%(B1)and 5.0%(B2)biochar Kg^(−1) of soil)for 5 days,followed by exposure to Na_(2)AsO_(4)(’B1+AsV’and’B2+AsV’)for 9 days.Maize plants exposed to AsV only accumulated substantial amount of arsenic in both roots and leaves,triggering severe phytotoxic effects,including stunted growth,leaf-yellowing,chlorosis,reduced photosynthesis,and nutritional imbalance,when compared with control plants.Contrariwise,biochar addition improved the phenotype and growth of AsV-stressed maize plants by reducing root-to-leaf AsV translocation(by 46.56 and 57.46%in‘B1+AsV’and‘B2+AsV’plants),improving gas-exchange attributes,and elevating chlorophylls and mineral levels beyond AsV-stressed plants.Biochar pretreatment also substantially counteracted AsV-induced oxidative stress by lowering reactive oxygen species accumulation,lipoxygenase activity,malondialdehyde level,and electrolyte leakage.Less oxidative stress in‘B1+AsV’and‘B2+AsV’plants likely supported by a strong antioxidant system powered by biochar-mediated increased activities of superoxide dismutase(by 25.12 and 46.55%),catalase(51.78 and 82.82%),and glutathione S-transferase(61.48 and 153.83%),and improved flavonoid levels(41.48 and 75.37%,respectively).Furthermore,increased levels of soluble sugars and free amino acids also correlated with improved leaf relative water content,suggesting a better osmotic acclimatization mechanism in biochar-pretreated AsV-exposed plants.Overall,our findings provided mechanistic insight into how biochar facilitates maize’s active recovery from AsV-stress,implying that biochar application may be a viable technique for mitigating negative effects of arsenic in maize,and perhaps,in other important cereal crops.

Contribution of Genomics to Gene Discovery in Plant Abiotic Stress Responses

Sustaining agricultural production under adverse environ- mental conditions, such as drought and high salinity, rep- resents a major challenge. The discovery of key genes and signal transduction pathways underlying plant responses to environmental stress will play an important role in devel- oping strategies for the genetic improvement of crops to address this challenge. Crop functional genomics has greatly contributed to the identification of abiotic stress-related genes. Current advances in genomic technologies now pro- vide effective and high-throughput methods for identifying stress-related genes at a genome-wide level, especially with the availability of the complete genomic sequence of several model and crop plant species. The development of genetic database resources has allowed bioinformatic approaches to identify stress-tolerant gene families across species based on homology and synteny. Additionally, genome-wide associa- tion studies （GWAS） for complex trait loci in crops have facili- tated the discovery of critical stress-related genes and their favorable alleles.