Abscisic Acid Levels Research Articles

Proper doses of brassinolide enhance somatic embryogenesis in different competent Korean pine cell lines during embryogenic callus differentiation.

Somatic embryogenesis of Korean pine (Pinus koraiensis Sieb. Et Zucc.), an ecologically and econimically very important conifer species, was hindered by the gradually weakens and fast runaway of the embryogenicity and embryo competence of the embryogenic callus. Brassinolide (BL) has shown the enhancing capability of somatic embryo regeneration. For checking the function of BL in this issue, we applied different concentrations of BL to Korean pine callus materials exhibiting different embryogenic capacities and subsequently monitored the physiological alterations and hormone dynamics of the embryogenic callus. Our study revealed that calli with different embryogenic strengths responded differently to different concentrations of BL, but the effect after the addition of BL was very uniform. The addition of BL during the proliferation phase of embryogenic callus may help to stimulate the biological activity of callus during the proliferation process and improve the level of cell metabolism, which is accompanied by a reduction in storage substances. BL could reduce the level of endogenous auxin IAA in embryogenic callus and increase the level of abscisic acid to regulate cell division and differentiation. In addition, the MDA content in the callus was significantly decreased and the activity of antioxidant enzymes was significantly increased after the addition of BL. During the proliferation of embryogenic callus, BL was added to participate in the metabolism of phenylpropane in the cells and to increase the activity of phenylalanine ammonia-lyase and the content of lignin in the cells. We deduced that the proper doses of BL for Korean pine embryogenic callus culture were as follow: calli with low, high and decreasing embryogenicity were subcultured after the addition of 0.75 mg/L, 0.35 mg/L, 2.00 mg/L BL, respectively, during proliferation culture stage.

Unlocking nature's stress buster: Abscisic acid's crucial role in defending plants against abiotic stress

The main obstacle for sustained supply of agricultural products and feeding the globe in the coming years is abiotic stress. Plants typically shorten their developmental processes under stress, which eventually has a negative impact on production. A key phytohormone that plays crucial role in combating abiotic stress is abscisic acid (ABA). ABA plays a significant role in absorbing stress signals and guiding subsequent stress responses. For an outcome, plants must consistently control ABA levels in response to shifting environmental factors. In addition to helping plants adapt to diverse conditions like drought, salt, temperature stress, ABA also controls a number of physiological functions, including stomatal opening and protein synthesis. A variety of defense mechanisms against stress are regulated by ABA, which is produced in various organs in response to stressful situations. These defense mechanisms include controlling stomatal aperture and the expression of genes that confer resistance against environmental stresses. Based on the current available literatures, this review provides insights of ABA's function in plants in context of abiotic stresses, with a focus on its synthesis, signaling pathways, regulatory functions, impact on root architecture, control over stomatal movement, and its intricate interactions with other phytohormones.

Integrative effects of phytohormones in the phenolic acids production in Salvia verticillata L. under multi-walled carbon nanotubes and methyl jasmonate elicitation

Salvia verticillata L. is a well-known herb rich in rosmarinic acid (RA) and with therapeutic values. To better understand the possible roles of phytohormones in the production of phenolic acids in S. verticillata, in this work, we investigated some physiological and biochemical responses of the species to methyl jasmonate (MJ) and multi-walled carbon nanotubes (MWCNTs) as two effective elicitors. The leaves were sprayed with aqueous solutions containing 100 mg L−1 MWCNTs and 100 µM MJ and then harvested during interval times of exposure up to 96 h. The level of abscisic acid, as the first effective phytohormone, was altered in the leaves in response to MJ and MWCNTs elicitation (2.26- and 3.06-fold more than the control, respectively), followed by significant increases (P ˂ 0.05) detected in jasmonic acid and salicylic acid contents up to 8 h after exposure. Obtained data revealed that simultaneously with changes in phytohormone profiles, significant (P ˂ 0.05) rises were observed in the content of H2O2 (8.85- and 9.74-folds of control), and the amount of lipid peroxidation (10.18- and 17.01-folds of control) during the initial times after exposure to MJ and MWCNTs, respectively. Later, the content of phenolic acids increased in the elicited leaves due to changes in the transcription levels of key enzymes involved in their biosynthesis pathways, so 2.71- and 11.52-fold enhances observed in the RA content of the leaves after exposure to MJ and MWCNTs, respectively. It is reasonable to conclude that putative linkages between changes in some phytohormone pools lead to the accumulation of phenolic acids in the leaves of S. verticillata under elicitation. Overall, the current findings help us improve our understanding of the signal transduction pathways of the applied stimuli that led to enhanced secondary metabolite production in medicinal plants.

Physiological Mechanisms Underlying Tassel Symptom Formation in Maize Infected with Sporisorium reilianum.

Head smut is a soil-borne fungal disease caused by Sporisorium reilianum that infects maize tassels and ears. This disease poses a tremendous threat to global maize production. A previous study found markedly different and stably heritable tassel symptoms in some maize inbred lines with Sipingtou blood after infection with S. reilianum. In the present study, 55 maize inbred lines with Sipingtou blood were inoculated with S. reilianum and classified into three tassel symptom types (A, B, and C). Three maize inbred lines representing these classes (Huangzao4, Jing7, and Chang7-2, respectively) were used as test materials to investigate the physiological mechanisms of tassel formation in infected plants. Changes in enzyme activity, hormone content, and protein expression were analyzed in all three lines after infection and in control plants. The activities of peroxidase (POD), superoxide dismutase (SOD), and phenylalanine-ammonia-lyase (PAL) were increased in the three typical inbred lines after inoculation. POD and SOD activities showed similar trends between lines, with the increase percentage peaking at the V12 stage (POD: 57.06%, 63.19%, and 70.28% increases in Huangzao4, Jing7, and Chang7-2, respectively; SOD: 27.01%, 29.62%, and 47.07% in Huangzao4, Jing7, and Chang7-2, respectively. These were all higher than in the disease-resistant inbred line Mo17 at the same growth stage); this stage was found to be key in tassel symptom formation. Levels of gibberellic acid (GA3), indole-3-acetic acid (IAA), and abscisic acid (ABA) were also altered in the three typical maize inbred lines after inoculation, with changes in GA3 and IAA contents tightly correlated with tassel symptoms after S. reilianum infection. The differentially expressed proteins A5H8G4, P09233, and Q8VXG7 were associated with changes in enzyme activity, whereas P49353, P13689, and P10979 were associated with changes in hormone contents. Fungal infection caused reactive oxygen species (ROS) and nitric oxide (NO) bursts in the three typical inbred lines. This ROS accumulation caused biofilm disruption and altered host signaling pathways, whereas NO signaling triggered strong secondary metabolic responses in the host and altered the activities of defense-related enzymes. These factors together resulted in the formation of varying tassel symptoms. Thus, interactions between S. reilianum and susceptible maize materials were influenced by a variety of signals, enzymes, hormones, and metabolic cycles, encompassing a very complex regulatory network. This study preliminarily identified the physiological mechanisms leading to differences in tassel symptoms, deepening our understanding of S. reilianum-maize interactions.

Effect of calcium and magnesium on starch synthesis in maize kernels and its physiological driving mechanism.

The content of kernel starch (STC), which is a fundamental indicator of the nutritional value of maize, is directly correlated with the grain's taste and aroma. Both calcium (Ca) and magnesium (Mg) are critical nutrients that play a significant role in the growth and development of maize, as well as in the synthesis of STC. To determine the physiological driving mechanisms of Ca and Mg effects on the accumulation of STC synthesis in maize kernels and the characteristics of their effects on endogenous hormones and enzymes of STC synthesis in maize leaves, our study applied foliar Ca and Mg fertilizers at various levels to maize prior to pollination. (1) The levels of Ca, Mg, indole-3-acetic acid (IAA), gibberellin (GA), and zeatin riboside (ZR) in maize leaves increased and then decreased after the supplementation of Ca and Mg. They peaked on the 32nd day after pollination. In contrast, the levels of abscisic acid (ABA) initially decreased and then increased. Ca and Mg had a negative correlation with ABA and a positive correlation with IAA, GA, and ZR. (2) As the levels of Ca and Mg increased, correspondingly rose the activities of enzymes responsible for STC synthesis and the content of STC and its components. Principally influencing the synthesis of STC were ABA, IAA, uridine diphosphate-glucose pyrophosphorylase (UDPG), granule-bound starch synthase (GBSS), and soluble starch synthase (SSS). (3) "IAA-UDPG or GBSS-STC" was the predominant physiological regulation pathway of Ca on kernel STC, whereas "IAA-GBSS-STC" was the dominant physiological regulation pathway of Mg on kernel STC. The regulatory impact of STC by UDPG and GBSS was positive, as were the effects of IAA on UDPG and GBSS. In conclusion, the accumulation of kernel starch was significantly enhanced by Ca and Mg supplementation via the modulation of endogenous hormone levels and key enzyme activities. This research identifies a viable approach to improve the nutritional composition of maize.

Integrated Analysis of Transcriptome and Metabolome to Unveil Impact on Enhancing Grape Aroma Quality with Synthetic Auxin: Spotlight the Mediation of ABA in Crosstalk with Auxin.

It is widely accepted that prevéraison application of naphthaleneacetic acid (NAA) can delay the ripening of grapes and improve their quality. However, how NAA impacts grape aroma compound concentrations remains unclear. This study incorporated the analyses of aroma metabolome, phytohormones, and transcriptome of Vitis vinifera L. cv. Cabernet Sauvignon grapes cultivated in continental arid/semiarid regions of western China. The analyses demonstrated that NAA application increased β-damascenone and 1,1,6-trimethyl-1,2-dihydronaphthalene (TDN) in the harvested grapes by delaying véraison and upregulating VvPSY1 and VvCCD4b expressions. Additionally, NAA treatment decreased 2-isobutyl-3-methoxypyrazine (IBMP) at the same phenological stage. Notably, abscisic acid (ABA) levels increased in NAA-treated grapes during véraison, which triggered further changes in norisoprenoid metabolisms. The ABA-responsive factor VvABF2 was potentially involved in VvPSY1 positive modulation, while the auxin response factor VvARF10 may play a role in VvCCD4b upregulation and VvOMT2 downregulation during NAA induction. VvARF10 possibly acts as a crosstalk node between the ABA and auxin signaling pathways following NAA treatment in regulating aroma biosynthesis.

Transcriptomic and physiological analyses reveal that jasmonic acid and abscisic acid coordinately regulate cold stress response in Myriophyllum aquaticum

Myriophyllum aquaticum, renowned for its ability to purify aquaculture wastewater, faces a significant challenge due to its susceptibility to cold stress. However, the molecular mechanisms underlying M. aquaticum's response to cold stress remain poorly understood. In this study, we unraveled the molecular mechanisms governing M. aquaticum's response to cold stress through transcriptome sequencing and physiological analyses. Our investigation revealed 12,684 differentially expressed genes during cold stress. Gene ontology and KEGG analyses demonstrated the involvement of plant hormone signaling and transcriptional reprogramming related genes in M. aquaticum's response to cold stress. Further investigations highlighted the role of jasmonic acid (JA) and abscisic acid (ABA) in M. aquaticum's cold acclimation. Firstly, cold stress significantly increased endogenous levels of JA and ABA in M. aquaticum plants. Secondly, the transcript levels of several crucial JA and ABA signaling genes were prominently elevated, as shown by expression profiling and qRT-PCR analyses. Thirdly, the application of exogenous JA or ABA effectively mitigated foliar damage and improved cold tolerance in M. aquaticum plants. Furthermore, the expression of JA and ABA biosynthesis and signaling genes was significantly upregulated in JA- or ABA-pretreated plants when exposed to cold stress. Collectively, our findings provide evidence that JA and ABA contribute to the cold acclimation of M. aquaticum plants. Our research provides insights into the molecular mechanisms underlying cold acclimation of M. Aquaticum plants and presents a novel strategy to improve their cold tolerance, thereby expanding their potential application in phytoremediation efforts in high latitude areas.

ZmHDT103 Negatively Regulates Drought Stress Tolerance in Maize Seedlings

Drought stress presents a significant threat to the growth and development of maize. It is important to study the genes and mechanisms that contribute to drought tolerance. In this study, we identified ZmHDT103 (that encodes a histone deacetylase) by conducting a homologous sequence comparison and found that the expression of ZmHDT103 in maize seedlings is responsive to treatment with polyethylene glycol (PEG). We utilized CRISPR/Cas9 gene editing technology to generate three distinct knockout lines and obtained the ChinaMU mutant of the ZmHDT103 gene. Under drought conditions, the seedlings of ZmHDT103 mutants exhibited significantly lower water loss rate (WLR), relative electrolytic leakage (REL), hydrogen peroxide (H2O2) level, and malonaldehyde (MDA) level than those of their wild-type (WT) counterparts. Additionally, the seedlings of ZmHDT103 mutants exhibited significantly higher levels of abscisic acid (ABA), relative water content (RWC), peroxidase (POD), and proline (Pro) than those of the WT control. These findings indicate that ZmHDT103 acts as a negative regulator of drought tolerance in maize.

Salicylic acid mitigates 'Hayward' kiwifruit chilling injury by regulating hormone and proline metabolism, as well as maintaining cellular structure

The 'Hayward' kiwifruit is extremely susceptible to chilling injury (CI) during the late stages of cold storage, thus limiting its storage quality and life. Therefore, mitigating the losses caused by CI is imperative. Salicylic acid (SA) has been demonstrated to mitigate CI in fruit and vegetables. In this study, we conducted a comparative analysis of proline metabolism, key endogenous hormone levels, as well as the effects on cell structure and membrane lipid oxidation in kiwifruit treated with 1 mM SA during low-temperature storage. The results showed that SA could attenuate lipoxygenase (LOX) activity, enhance catalase (CAT) activity, suppress the elevation of malondialdehyde (MDA) content, mitigate starch granule degradation in cells, and preserve cell structure integrity. Moreover, SA was found to enhance proline biosynthesis by activating ornithine transaminase (OAT) and pyrroline-5-carboxylate synthase (P5CS) while concurrently suppressing proline dehydrogenase (PDH) activity. Additionally, exogenous SA increased endogenous levels of both SA and abscisic acid (ABA), while simultaneously decreasing the concentration of gibberellic acid (GA) in fruit. In conclusion, exogenous SA treatment could alleviate the development of CI in kiwifruit by maintaining cell structure, promoting proline synthesis, and balancing endogenous hormone content. Our study offers a theoretical foundation for understanding the mechanism by which SA mitigates cold damage in kiwifruit, and provides novel insights into the low-temperature preservation of kiwifruit.

Abscisic acid inhibits germination of Striga seeds and is released by them likely as a rhizospheric signal supporting host infestation.

Seeds of the root parasitic plant Striga hermonthica undergo a conditioning process under humid and warm environments before germinating in response to host-released stimulants, particularly strigolactones (SLs). The plant hormone abscisic acid (ABA) regulates different growth and developmental processes, and stress response; however, its role during Striga seed germination and early interactions with host plants is under-investigated. Here, we show that ABA inhibited Striga seed germination and that hindering its biosynthesis induced conditioning and germination in unconditioned seeds, which was significantly enhanced by treatment with the SL analog rac-GR24. However, the inhibitory effect of ABA remarkably decreased during conditioning, confirming the loss of sensitivity towards ABA in later developmental stages. ABA measurement showed a substantial reduction of its content during the early conditioning stage and a significant increase upon rac-GR24-triggered germination. We observed this increase also in released seed exudates, which was further confirmed by using the Arabidopsis ABA-reporter GUS marker line. Seed exudates of germinated seeds, containing elevated levels of ABA, impaired the germination of surrounding Striga seeds in vitro and promoted root growth of a rice host towards germinated Striga seeds. Application of ABA as a positive control caused similar effects, indicating its function in Striga/Striga and Striga/host communications. In summary, we show that ABA is an essential player during seed dormancy and germination processes in Striga and acts as a rhizospheric signal likely to support host infestation.

Accumulation of Salicylic Acid and 12-oxo-phytodienoic Acid Acting on the Antioxidant Pathway to Keep Stability of Striped Leaves of Variegated Temple Bamboo

Variegated temple bamboo (Sinobambusa tootsik f. luteoloalbostriata) is one of the native variegated bamboo species has some whole green (WG) and whole white (WW) leaves in addition to striped green and white ones. The life span of WW leaves is short, but the life span of striped leaves (SLs) is unaffected by the area of white mesophyll, and the SL phenotype is well maintained. To explore the mechanism of phenotypic stability of SL, we took five leaf phenotypes as study materials: WG, WW, SL, the green part of SL (SG), and the white part of SL (SW). Through the measurement of photosynthetic pigments, leaf nutrient elements, chloroplast synthesis–related hormones and their precursors in the leaves, and antioxidant system parameters, we examined the antioxidant adaptation mechanism of the white mesophyll cells of S. tootsik f. luteoloalbostriata. The results indicated that abscisic acid (ABA) levels were substantially higher in WW leaves than in SW leaves, and salicylic acid (SA) levels were significantly higher in SW leaves compared with WW leaves. Levels of 12-oxo-phytodienoic acid (OPDA), and SA were substantially higher in WW and SW than in the leaves of the other three phenotypes. Glutathione (GSH) levels were substantially higher in SW than in SG and reactive oxygen species (ROS) levels were significantly lower. Overall, the white mesophyll cells of S. tootsik f. luteoloalbostriata had strong antioxidant properties. SA and OPDA jointly act on the antioxidant pathway to reduce the content of ROS in leaves, thus ensuring the stability of SL.

Rhizobium rhizogenes rolC gene promotes leaf senescence and enhances osmotic stress resistance in Arabidopsis: the positive role of abscisic acid

AbstractThe root oncogenic loci (rol) C oncogene has been identified as a key player during the plant‐Rhizobium rhizogenes interaction and is considered to confer resistance to plant abiotic stresses, yet the underlying mechanisms remain largely elusive. In this study, Arabidopsis plants constitutively overexpressing rolC were produced. Biometric analysis showed that rolC induced diverse phenotypic modifications, including dwarfism, increased number of stem branches (1.3 times more than WT), weak root growth, early flowering (1.6 days earlier than WT) and premature leaf senescence. In addition, senescence stimulus (exogenous ethylene: 10 or 100 μL L−1) and 10% (w/v) polyethylene glycol 6000 (PEG) treatments demonstrated that rolC mediated leaf abscisic acid (ABA) enhancement in Arabidopsis, and this might be involved in rolC‐induced premature leaf senescence and resistance enhancement to osmotic stress. It is concluded that rolC‐induced premature leaf senescence may be involved in an abiotic stress escape mechanism in Arabidopsis, which is closely related to the increase of endogenous ABA levels. These findings provide new insights into the role of rolC in plant‐bacterial interaction and uncover the potential of biotechnological application associated with R. rhizogenes/rol genes in plant drought defense.

Passive stomatal closure under extreme drought in an angiosperm species.

The phytohormone abscisic acid (ABA) plays a major role in closing the stomata of angiosperms. However, recent reports of some angiosperm species having a peaking-type ABA dynamic, in which under extreme drought ABA levels decline to pre-stressed levels, raises the possibility that passive stomatal closure by leaf water status alone can occur in species from this lineage. To test this hypothesis, we conducted instantaneous rehydration experiments in the peaking-type species Umbellularia californica through a long-term drought, in which ABA levels declined to pre-stress levels, yet stomata remain closed. We found that when ABA levels were lowest during extreme drought, stomata reopen rapidly to maximum rates of gas exchange on instantaneous rehydration, suggesting that the stomata of U. californica were passively closed by leaf water status alone. This contrasts with leaves early in drought, in which ABA levels were highest and stomata did not reopen on instantaneous rehydration. The transition from ABA-driven stomatal closure to passively driven stomatal closure as drought progresses in this species occurs at very low water potentials facilitated by highly embolism-resistant xylem. These results have important implications for understanding stomatal control during drought in angiosperms.

Transcriptomic and metabolomic analysis of changes in grain weight potential induced by water stress in wheat

The sink strength of developing ovaries in wheat determines the grain weight potential. The period from booting to the grain setting stage is critical for ovary growth and development and potential sink capacity determination. However, the underlying regulatory mechanism during this period by which the wheat plant balances and coordinates the floret number and ovary/grain weight under water stress has not been clarified. Therefore, we designed two irrigation treatments of W0 (no seasonal irrigation) and W1 (additional 75 mm of irrigation at the jointing stage) and analyzed the responses of the ovary/grain weight to water stress at the phenotypic, metabolomic, and transcriptomic levels. The results showed that the W0 irrigation treatment reduced the soil water content, plant height, and green area of the flag leaf, thus reducing grain number, especially for the inferior grains. However, it improved the grain weight of the superior and inferior grains as well as average grain weight at maturity, while the average ovary/grain weight and volume during –3 to 10 days after anthesis (DAA) also increased. Transcriptomic analysis indicated that the genes involved in both sucrose metabolism and phytohormone signal transduction were prominently accelerated by the W0 treatment, accompanied by greater enzymatic activities of soluble acid invertase (SAI) and sucrose synthase (Sus) and elevated abscisic acid (ABA) and indole-3-acetic acid (IAA) levels. Thus, the sucrose content decreased, while the glucose and fructose contents increased. In addition, several TaTPP genes (especially TaTPP-6) were down-regulated and the IAA biosynthesis genes TaTAR1 and TaTAR2 were up-regulated under the W0 treatment before anthesis, which further increased the IAA level. Collectively, water stress reduced the growth of vegetative organs and eliminated most of the inferior grains, but increased the ABA and IAA levels of the surviving ovaries/grains, promoting the enzymatic activity of Sus and degrading sucrose into glucose and fructose. As a result, the strong sucrose utilization ability, the enhanced enzymatic activity of SAI and the ABA- and IAA-mediated signaling jointly increased the weight and volume of the surviving ovaries/grains, and ultimately achieved the trade-off between ovary/grain weight and number in wheat under water stress.

Long-term drought modifies carbon allocation and abscisic acid levels in five forest tree species

Long-term drought modifies carbon allocation and abscisic acid levels in five forest tree species

Zmhdz9, an HD-Zip transcription factor, promotes drought stress resistance in maize by modulating ABA and lignin accumulation

Maize is the largest crop in the world in terms of both planting area and total yield, and it plays a crucial role in ensuring global food and feed security. However, in recent years, with climate deterioration, environmental changes, and the scarcity of freshwater resources, drought has become a serious limiting factor for maize yield and quality. Drought stress-induced signals undergo a series of transmission processes to regulate the expression of specific genes, thereby affecting the drought tolerance of plants at the tissue, cellular, physiological and biochemical levels. Therefore, in this study we investigated the HD-Zip transcription factor gene Zmhdz9, and yeast activation experiments demonstrated that Zmhdz9 exhibited transcriptional activation activity. Under drought stress, high abscisic acid (ABA) and lignin levels significantly improved drought resistance in maize. Yeast two-hybrid, bimolecular fluorescence complementation (BIFC) and pull-down experiments showed that Zmhdz9 interacted with ZmWRKY120 and ZmTCP9, respectively. Overexpression of Zmhdz9 and gene editing of ZmWRKY120 or ZmTCP9 improved maize drought resistance, indicating their importance in the drought stress response. Furthermore, Zmhdz9 promoted the direct transcription of ZmWRKY120 in the W-box, activating elements of the ZmNCED1 promoter, which encodes a key enzyme in ABA biosynthesis. Additionally, Zmhdz9 promoted direct transcription of ZmTCP9 in the GGTCA motif, activating elements of the ZmKNOX8 promoter, which encodes a key enzyme in lignin synthesis. This study showed that the regulation of ABA and lignin by Zmhdz9 is essential for drought stress resistance in maize.

Impact of biostimulants based amino acids and irrigation frequency on agro-physiological characteristics and productivity of broccoli plants

Abstract scientists are concerned about the utilizing of biostimulants-based amino acids in plant feeding and mitigating negative effects of water stress. As a result, two-year field experiments were conducted at Faculty of Agriculture's experimental station at Cairo University to study the effectiveness of liquid yeast waste (CMS) and Cargo amino acids (AAs) on the agro-physiological features of broccoli plants with different irrigation frequencies (every 5, 10, and 15 days). Compared with control plants, the foliar application of AAs and CMS significantly increased plant height, photosynthesis pigments, head weight, head diameter, head height, plant yield, and quality at different irrigation frequencies. Likewise, both treatments (CMS and AAs) significantly improved ascorbic acids by 16.65% and 15.95% and increased total phenol content by 24.10% and 36.60%, respectively, compared to control plants. Accordingly, the highest productivity was achieved for broccoli grown under irrigation every five days with the CMS bio-stimulant, where it was 3111.17 kg ha-1, while the lowest productivity was achieved for the control treatment in which no biostimulants were added and irrigation frequency every 15 days, and the productivity was 1376.22 kg ha-1. Plants irrigated every 15 days produced the highest levels of abscisic acid (ABA) and superoxide dismutase (SOD), followed by plants irrigated every 10 days and every 5 days. Exogenous application of amino acids bio-stimulants could be suggested to improve vegetative growth, biochemical characteristics, productivity, and nutritional value as well as to mitigate negative effects of water scarcity.

Ascorbate oxidation stimulates rice root growth via effects on auxin and abscisic acid levels

Ascorbate oxidation stimulates rice root growth via effects on auxin and abscisic acid levels

Abscisic acid biosynthesis, metabolism and signaling in ripening fruit.

Fruits are highly recommended nowadays in human diets because they are rich in vitamins, minerals, fibers and other necessary nutrients. The final stage of fruit production, known as ripening, plays a crucial role in determining the fruit's quality and commercial value. This is a complex physiological process, which involves many phytohormones and regulatory factors. Among the phytohormones involved in fruit ripening, abscisic acid (ABA) holds significant importance. ABA levels generally increase during the ripening process in most fruits, and applying ABA externally can enhance fruit flavor, hasten softening, and promote color development through complex signal regulation. Therefore, gaining a deeper understanding of ABA's mechanisms in fruit ripening is valuable for regulating various fruit characteristics, making them more suitable for consumption or storage. This, in turn, can generate greater economic benefits and reduce postharvest losses. This article provides an overview of the relationship between ABA and fruit ripening. It summarizes the effects of ABA on ripening related traits, covering the biochemical aspects and the underlying molecular mechanisms. Additionally, the article discusses the interactions of ABA with other phytohormones during fruit ripening, especially ethylene, and provides perspectives for future exploration in this field.

Structural insights into AtABCG25, an angiosperm-specific abscisic acid exporter

Cellular hormone homeostasis is essential for precise spatial and temporal signaling responses and plant fitness. Abscisic acid (ABA) plays pivotal roles in orchestrating various developmental and stress responses and confers fitness benefits over ecological and evolutionary timescales in terrestrial plants. Cellular ABA level is regulated by complex processes, including biosynthesis, catabolism, and transport. AtABCG25 is the first ABA exporter identified through genetic screening and affects diverse ABA responses. Resolving the structural basis of ABA export by ABCG25 is critical for further manipulations of ABA homeostasis and plant fitness. We used cryo-electron microscopy to elucidate the structural dynamics of AtABCG25 and successfully characterized different states, including apo AtABCG25, ABA-bound AtABCG25, and ATP-bound AtABCG25 (E232Q). Notably, AtABCG25 forms a homodimer that features a deep, slit-like cavity in the transmembrane domain, and we precisely characterized the critical residues in the cavity where ABA binds. ATP binding triggers closure of the nucleotide-binding domains and conformational transitions in the transmembrane domains. We show that AtABCG25 belongs to a conserved ABCG subfamily that originated during the evolution of angiosperms. This subfamily neofunctionalized to regulate seed germination via the endosperm, in concert with the evolution of this angiosperm-specific, embryo-nourishing tissue. Collectively, these findings provide valuable insights into the intricate substrate recognition and transport mechanisms of the ABA exporter AtABCG25, paving the way for genetic manipulation of ABA homeostasis and plant fitness.