ABA Levels Research Articles

Plant-Specific AtS40.4 Acts as a Negative Regulator in Abscisic Acid Signaling During Seed Germination and Seedling Growth in Arabidopsis.

Abscisic acid (ABA) is an important phytohormone regulating plant growth, development and stress responses. A multitude of key factors implicated in ABA signaling have been identified; however, the regulation network of these factors needs for further information. AtS40.4, a plant-specific DUF584 domain-containing protein, was identified previously as a senescence regulator in Arabidopsis. In this study, our finding showed that AtS40.4 was negatively involved in ABA signaling during seed germination and early seedling growth. AtS40.4 was highly expressed in seeds and seedlings, and the expression level was promoted by ABA. AtS40.4 was localized both in the nucleus and the cytoplasm. Moreover, the subcellular localization pattern of AtS40.4 was affected by ABA. The knockdown mutants of AtS40.4 exhibited an increased sensitivity to ABA, whereas the overexpression of AtS40.4 decreased the ABA response during seed germination and seedling growth of Arabidopsis. Furthermore, AtS40.4 was involved in ABRE-dependent ABA signaling and influenced the expression levels of ABA INSENTIVE (ABI)1-5 and SnRK2.6. Further genetic evidence demonstrated that AtS40.4 functioned upstream of ABI4. These findings support the notion that AtS40.4 is a novel negative regulator of the ABA response network during seed germination and early seedling growth.

Comparative analysis of the gene expression profile under two cultivation methods reveals the critical role of ABA in grape quality promotion

Root restriction is a critical cultivation technique that accelerates ripening and improves fruit quality, by a still unknown mechanism. ABA is an important phytohormone in both ripening and stress responses. To elucidate the relationship between ABA content and root restriction-induced fruit quality promotion, the endogenous ABA level was investigated in five-year-old ‘Muscat Hamburg’ grapevines from the pre-anthesis stage to maturity. The results showed that ABA production was significantly enhanced by root restriction. A transcriptomics-based approach was taken to identify transcriptionally regulated genes associated with ABA biosynthesis, catabolism and signal transduction in the four development periods of grape. A total of 2873 (884 upregulated and 1989 downregulated) DEGs were identified in all stages. Those related to metabolic processes, cellular processes, responses to stimuli, biological regulation and signal transduction were abundant in the biological process GO category. KEGG analysis revealed that plant hormone signal transduction and carotenoid biosynthesis were enriched out of the 127 total pathways. 12 DEGs involved in ABA biosynthesis and catabolism and 69 DEGs involved in plant hormone signal transduction were significantly regulated by root restriction. Twelve DEGs related to the biosynthesis and catabolism of ABA or plant hormone signal transduction were selected to validate the data obtained by RNA-Seq, and the results showed that genes such as PP2C, NCED, AAO3, ABA3, and CYP707A1, involved in ABA biosynthesis and signal transduction, may play important roles in the promotion of fruit quality by root restriction. This study suggests a potential ABA-mediated mechanism by which root-restriction cultivation promotes fruit ripening.

Transcriptome analysis of Chongyi wild mandarin, a wild species more cold-tolerant than Poncirus trifoliata, reveals key pathways in response to cold

Much effort has been made on the dissection of cold response in citrus, but relevant study in wild germplasm has been rare. Based on the result of the membership function value analysis with 12 physiological indexes, we reported a wild citrus germplasm, Chongyi wild mandarin (Citrus reticulata), which was more cold-tolerant than a cold-hardy rootstock, Poncirus trifoliata. To gain an overview of transcriptome changes under cold, leaves of Chongyi wild mandarin were sampled at 0, 1, 5 d after 0 °C treatment, and sequenced using an Illumina sequencing platform. Totally, 3921 and 5995 differentially expressed genes (DEGs) were identified in 1 d and 5 d, respectively. And then, RNA-seq results were further validated via real-time quantitative PCR with 17 DEGs. Many DEGs related to various cold signaling pathways were identified, especially those related to brassinosteroid cascade. Around 10 % of the total DEGs were transcription factors from 67 families, suggesting that transcriptional regulation, both C-repeat/dehydration responsive element-binding factor-dependent/independent pathways, was crucial for the cold tolerance of Chongyi wild mandarin. Our data also revealed that the transcriptional levels of many DEGs related to anti-oxidant enzymes and osmoprotectants metabolism were altered, which were consistent with the results of physiological experiments. Moreover, a number of DEGs involved in ABA, BR, GA metabolisms were isolated. Accordingly, the levels of ABA and BR were significantly increased under cold, but GAs were decreased. Taken together, this work provided a comprehensive view of physiological and transcriptional alterations in cold response of Chongyi wild mandarin.

Dynamics of Water and Abscisic Acid During Embryogeny and Embryo Drying in the Recalcitrant Seeds of Vateria indica L.

Vateria indica L. is a critically endangered tree species in South-Western Ghats of India, commercially exploited for its valuable resins. Seed recalcitrance is a major problem hindering the natural regeneration of this species and it poses a great challenge in seed storage and conservation. There was a continuous import of water from the maternal tissues to seed tissues till maturity and the seeds were released in a fully hydrated state. Differential accumulation of water has been noticed in the cotyledons and embryonal axis. There was a positive correlation between seed moisture content and rate of germination which is a character of recalcitrant seeds. The critical moisture content was found to be 40% in the axis and 23.5% in the cotyledons, below which the embryo will not germinate. Loss of germination ability as a result of desiccation was attributed to the cell membrane damage, expressed as the electrolyte leakage exceeding 0.79 μS/cm. ABA peaked in the mid embryogenesis, then dropped drastically and maintained a lower level till seed maturity. On desiccation, ABA started to increase but gradually dropped down. Both cotyledons and embryonal axis had differential ABA content but exhibited a general pattern of ABA level during embryogeny. Due to the thin seed coat/embryo ratio and low investment in the seed coat, this recalcitrant seed could not hold water as efficient as orthodox seeds. Thus, it germinated as soon as it was shed from the mother plant. On desiccation, ABA shot up and moisture content decreased along with electrolyte leakage and cell membrane damage. All these hindered germination of the seed. Thus, we can see a clear interplay between moisture content and ABA levels during embryogeny and desiccation. Since the seed biology of this species has not been well documented, the present work is mainly intended to study the dynamics of water and ABA during embryogeny and embryo drying. This study can surely contribute to the long-term storage and conservation of recalcitrant seeds which is a less explored area.

Foliar applied 24-epibrassinolide alleviates salt stress in rice (Oryza sativa L.) by suppression of ABA levels and upregulation of secondary metabolites

ABSTRACT Salt stress hinders plant growth and disrupts many physio-biochemical and molecular processes. The present study evaluated the potential role of foliar applied 24-epibrassinolide (EBR) for mitigating the adverse effects of salinity in rice plants. Our findings showed that salt stress reduced several growth and physiological parameters, and substantially increased oxidative stress in rice seedlings. The foliar application of EBR replenished the negative effects of salt stress by improving plant growth and physiological attributes in rice plants. Moreover, application of EBR substantially reduced oxidative injuries by enhancing antioxidant enzymes and phenolic compounds in rice plants during salt stress. Interestingly, the endogenous ABA levels were declined in stressed plants by EBR treatment, also validated by expression analysis of ABA-related genes. In addition, application of EBR upregulated carotenoids and flavonoids pathway genes, thus showing its function to activate secondary metabolism in rice plants during salt stress. The principal component analysis (PCA) indicated that, under salt stress, the response of EBR-treated rice plants was strongly correlated with the accumulation of phenolic compounds and flavonoids. Collectively, this study presents useful insight into the distinct role of EBR by activating underlying enzymatic and non-enzymatic defense mechanisms to mitigate salinity in rice plants.

ВЛИЯНИЕ ФЛУРИДОНА НА СОДЕРЖАНИЕ ГОРМОНОВ В КАЛЛУСАХ ЯЧМЕНЯ СОРТА STEPTOE И ЕГО АБК‑ДЕФИЦИТНОГО МУТАНТА AZ34

The effect of the inhibitor of endogenous ABA synthesis fluridone on the content and distribution of endogenous ABA and IAA in the calli of ABA-deficient mutant AZ34 barley and its parental cultivar Steptoe was studied using the methods of immuno-enzymatic solid-phase assay and immunolocalization of phytohormones. It was found that by the 4th week of in vitro culture, fluridone causes a significant decrease in the ABA level in calli of both genotypes compared to the control, and the inhibitory effect of fluridone in AZ34 is more pronounced than in Steptoe. In the calli of both genotypes, a significant increase in the IAA content was revealed against the background of a decrease in the ABA content upon treatment with fluridone as compared to the control. It was concluded that ABA plays an important role in the process of embryoido-genesis in vitro.

Exogenous β-cyclocitral treatment primes tomato plants against drought by inducing tolerance traits, independent of abscisic acid.

Drought is the most devastating stress for crops. Intensity and duration of drought determine the magnitude of plant damage; similarly, plant ability to counteract drought determines its tolerance capacity. Recent studies revealed that exogenous apocarotenoid treatment confers abiotic stress tolerance to plants. However, much less is known about the role of β-cyclocitral (βCC), the major apocarotenoid, in drought tolerance. Here, we demonstrate βCC's role in improving plants' tolerance against drought stress. Tomato (Solanum lycopersicum L.) plants were independently treated with water and βCC and grown under either water-limited or irrigated conditions. The βCC-treated drought-exposed (BD) and βCC-treated irrigated (BH) plants were analysed for the major drought tolerance associated traits; water-treated drought-exposed (CD) and water-treated irrigated plants (CH) were used as controls. On exposure to drought, unlike controls, βCC-treated plants showed no wilting, higher RWC and stomatal conductance, unchanged ABA levels and stomatal closure. The BD plants had increased photosynthesis, chlorophyll content and enhanced root, but not shoot, growth. In addition, βCC treatment enhanced proline accumulation and activity of SOD in both drought-exposed and well irrigated plants. Taken together, βCC was identified as a potential candidate that improves tomato osmolyte accumulation and superoxide elimination, independent of ABA, and prepares the plant for upcoming drought stress. Our results suggest that βCC can be used to prime crops against drought stress.

STIMULATION OF GROWTH AND OIL PRODUCTION IN CUMIN PLANT

A pot experiment was carried out during two successive seasons (2017/ 2018 and 2018/2019) at Medicinal and Aromatic Plants Research Department in Dokki. The aim of this work was to study the effect of foliar application of phenylalanine (Phe) and p -nitro phenylacetic acid (PNPAA) each of them alone at (0, 50,100 and 150 ppm) on cumin (Cuminum cyminum L.) plant growth, fruits yield, volatile oil production and its major chemical constituents. In general results indicated that, the foliar application of phenylalanine or p-nitrophenylacetic acid significantly increased vegetative growth expressed as (plant height, number of branches per plant) and produced higher fruits yield (g)/plant as well as volatile oil percentage and oil yield compared with control in the two seasons. Moreover, the highest values were obtained from phenylalanine or p-nitrophenylacetic acid at 150 ppm. Cumin plants showed more effective response to p-nitrophenylacetic acid (PNPAA) than phenylalanine (Phe). As for GLC analysis, the results showed that in general the highest percentage of p -menth-1-en7-ol and cumin aldehyde (p -isopropylbenzaldehyde) the main constituents in the volatile oil achieved with the treatment p-nitrophenylacetic acid at 150 ppm. The high concentration of phenylalanine and p-nitrophenylacetic acid (150 ppm) had significant increments in total phenols, total flavonoids and antioxidant activity compared with control. There was a significant increase in phenylalanine ammonia-lyase (PAL) activity compared to control. Also, there was an increment in IAA, GA3 and low level of ABA. It was observed that p -nitrophenylacetic acid (150 ppm) was superior to phenylalanine (150 ppm) in all afore mentioned characters

Integrated transcriptome and proteome analysis provides insight into chilling-induced dormancy breaking in Chimonanthus praecox

Chilling has a critical role in the growth and development of perennial plants. The chilling requirement (CR) for dormancy breaking largely depends on the species. However, global warming is expected to negatively affect chilling accumulation and dormancy release in a wide range of perennial plants. Here, we used Chimonanthus praecox as a model to investigate the CR for dormancy breaking under natural and artificial conditions. We determined the minimum CR (570 chill units, CU) needed for chilling-induced dormancy breaking and analyzed the transcriptomes and proteomes of flowering and non-flowering flower buds (FBs, anther and ovary differentiation completed) with different CRs. The concentrations of ABA and GA3 in the FBs were also determined using HPLC. The results indicate that chilling induced an upregulation of ABA levels and significant downregulation of SHORT VEGETATIVE PHASE (SVP) and FLOWERING LOCUS T (FT) homologs at the transcript level in FBs when the accumulated CR reached 570 CU (IB570) compared to FBs in November (FB.Nov, CK) and nF16 (non-flowering FBs after treatment at 16 °C for −300 CU), which suggested that dormancy breaking of FBs could be regulated by the ABA-mediated SVP-FT module. Overexpression in Arabidopsis was used to confirm the function of candidate genes, and early flowering was induced in 35S::CpFT1 transgenic lines. Our data provide insight into the minimum CR (570 CU) needed for chilling-induced dormancy breaking and its underlying regulatory mechanism in C. praecox, which provides a new tool for the artificial regulation of flowering time and a rich gene resource for controlling chilling-induced blooming.

Drought-tolerant coffee plants display increased tolerance to waterlogging and post-waterlogging reoxygenation

Soil waterlogging negatively impacts plants due to reduced oxygen availability in the rhizosphere. Here we selected two Coffea canephora clones with contrasting tolerance to drought and oxidative stress to test whether they would also exhibit contrasting tolerance to waterlogging and post-waterlogging reoxygenation. Plants were exposed to six days of waterlogging followed by 40 days of reoxygenation. During waterlogging, both clones exhibited lower leaf gas exchange rate, electron transport rate and photochemical quenching as well as increased non-photochemical quenching; overall, these changes were stronger in the drought tolerant (DT) clones over the drought sentitive (DS) ones. Photosynthetic limitations were essentially linked to diffusional constraints regardless of clone. In both clones, declines in stomatal conductance were not associated with foliar ABA or ethylene levels, however stomatal conductance correlated with the plant hydraulic conductance. After reoxygenation, DT plants mostly recovered leaf function and plant mortality was less than 10%. Conversely, DS plants displayed very low water potentials after reoxygenation, which was accompanied by photosynthetic and membrane damage and 40% plant mortality. Our findings confirmed that the DT clone is less impaired by soil waterlogging and reoxygenation than the DS one. The differences between clones were more evident during the reoxygenation than during waterlogging, likely due to the drought experienced by the DS but not DT plants. Collectively, this information leads us to a common path to find new coffee genotypes with increased tolerance to both drought and waterlogging aiming at increased coffee sustainability under an ongoing climate changing scenario.

Comprehensive transcriptome and proteome analyses reveal a novel sodium chloride responsive gene network in maize seed tissues during germination.

Germination is a plant developmental process by which radicle of mature seeds start to penetrate surrounding barriers for seedling establishment and multiple environmental factors have been shown to affect it. Little is known how high salinity affects seed germination of C4 plant, Zea mays. Preliminary germination assay suggested that isolated embryo alone was able to germinate under 200 mM NaCl treatment, whereas the intact seeds were highly repressed. We hypothesized that maize endosperm may function in perception and transduction of salt signal to surrounding tissues such as embryo, showing a completely different response to that in Arabidopsis. Since salt response involves ABA, we analysed in vivo ABA distribution and quantity and the result demonstrated that ABA level in isolated embryo under NaCl treatment failed to increase in comparison with the water control, suggesting that the elevation of ABA level is an endosperm dependent process. Subsequently, by using advanced profiling techniques such as RNA sequencing and SWATH-MS-based quantitative proteomics, we found substantial differences in post-transcriptional and translational changes between salt-treated embryo and endosperm. In summary, our results indicate that these regulatory mechanisms, such as alternative splicing, are likely to mediate early responses to salt stress during maize seed germination.

Cytokinin oxidase/dehydrogenase OsCKX11 coordinates source and sink relationship in rice by simultaneous regulation of leaf senescence and grain number.

SummaryThe flag leaf and grain belong to the source and sink, respectively, of cereals, and both have a bearing on final yield. Premature leaf senescence significantly reduces the photosynthetic rate and severely lowers crop yield. Cytokinins play important roles in leaf senescence and determine grain number. Here, we characterized the roles of the rice (Oryza sativa L.) cytokinin oxidase/dehydrogenase OsCKX11 in delaying leaf senescence, increasing grain number, and coordinately regulating source and sink. OsCKX11 was predominantly expressed in the roots, leaves, and panicles and was strongly induced by abscisic acid and leaf senescence. Recombinant OsCKX11 protein catalysed the degradation of various types of cytokinins but showed preference for trans‐zeatin and cis‐zeatin. Cytokinin levels were significantly increased in the flag leaves of osckx11 mutant compared to those of the wild type (WT). In the osckx11 mutant, the ABA‐biosynthesizing genes were down‐regulated and the ABA‐degrading genes were up‐regulated, thereby reducing the ABA levels relative to the WT. Thus, OsCKX11 functions antagonistically between cytokinins and ABA in leaf senescence. Moreover, osckx11 presented with significantly increased branch, tiller, and grain number compared with the WT. Collectively, our findings reveal that OsCKX11 simultaneously regulates photosynthesis and grain number, which may provide new insights into leaf senescence and crop molecular breeding.

HaASR1 gene cloned from a desert shrub, Haloxylon ammodendron, confers drought tolerance in transgenic Arabidopsis thaliana

Abiotic stresses pose adverse impact on plant growth and development and exploring the stress tolerance genes from dominant species is still urgent. The desert shrub, Haloxylon ammodendron, a C4 and succulent xero-halophyte species, has great drought and salt tolerance. Here, we reported the isolation and functions analysis of HaASR1 (abscisic acid, stress, and ripening) from H. ammodendron. HaASR1 interacts with HaPrxQ and HaBADH and may function in preventing PrxQ and BADH from denaturation in plants under drought stress. Overexpression of HaASR1 reduces the sensitivity of Arabidopsis plants to exogenous ABA and decreases the endogenous ABA level through down-regulating ABA biosynthesis genes under drought stress, which making the plants display less inhibition of shoot growth and enhanced drought tolerance. Overexpression of HaASR1 significantly enhances photosynthetic capacity of Arabidopsis plants under drought stress by reducing H2O2 accumulation through up-regulating AtCAT2, AtAPX1 and AtPrxQ and maintaining relatively integrity of chloroplasts. Overexpression of HaASR1 also significantly improves water-retaining ability. Taken together, we propose that HaASR1 plays critical roles in plant drought stress adaptation by making the plants partially defective in ABA signaling and participating in drought tolerance regulation through nonstomatal pathways, enhancing ROS-scavenging ability and water-retaining ability, which is different from the functions of previously reported ASR genes from other plant species. This research also reveals that HaASR1 gene from the desert shrub, Haloxylon ammodendron, has potential application values in improving abiotic stresses of other plant species by genetic engineering.

The seed-specific heat shock factor A9 regulates the depth of dormancy in Medicago truncatula seeds via ABA signalling.

During the later stages of seed maturation, two key adaptive traits are acquired that contribute to seed lifespan and dispersal, longevity and dormancy. The seed-specific heat shock transcription factor A9 is an important hub gene in the transcriptional network of late seed maturation. Here, we demonstrate that HSFA9 plays a role in thermotolerance rather than in ex situ seed conservation. Storage of hsfa9 seeds of Medicago truncatula and Arabidopsis had comparable lifespan at moderate storage relative humidity (RH), whereas at high RH, hsfa9 seeds lost their viability much faster than wild type seeds. Furthermore, we show that in M. truncatula, Mthsfa9 seeds acquired more dormancy during late maturation than wild type. Transient expression of MtHSFA9 in hairy roots and transcriptome analysis of Mthsfa9 Tnt1 insertion mutants identified a deregulation of genes involved in ABA biosynthesis, catabolism and signalling. Consistent with these results, Mthsfa9 seeds exhibited increased ABA levels and higher sensitivity to ABA. These data suggest that in legumes, HSFA9 acts as a negative regulator of the depth of seed dormancy during seed development via the modulation of hormonal balance.

Influence of Elevated pH on Germination, Growth Attributes and ABA Contents of Sticky Mouse-Ear Chickweed (Cerastium glomeratum Thuill.)

Sticky mouse-ear chickweed (Cerastium glomeratum Thuill.) is a dominant annual weed of Korea. Control management of such an exotic weed is a challenging task for agronomist and researcher over the years. We evaluated the effect of elevated pH levels on the germination, growth, chlorophyll content, nutrients and hormonal regulation of sticky mouse-ear chickweed under green-house conditions. Our results showed that pH have no significant effect on seed germination except pH3, which reduced germination rate by 10%. Maximum hypocotyl and radicle growth was observed at pH5 and pH7, while hypocotyl failed to emerge at pH 3. Plant growth attributes showed that plant height, fresh biomass, number of leaves and chlorophyll content were higher at pH7 and pH9; while lowest number of leaves (24.8 ± 2.8) and chlorophyll content (313.2 ± 11.2 SPAD) were recorded for pH3. The endogenous ABA levels were significantly higher at pH3 (71.22±5.4ng/g) but lowered at pH7 and pH9 (6.6±0.8 ng/g). The weed nutrients uptake result showed higher Fe (858.47 mg/kg) and Al (835.05 mg/kg) at pH 3 and pH 5; while higher Ca content (4887.2 mg/kg) was observed at pH 5. It was concluded that use of varying pH can play a vital role in the weed management, although its possible adverse impact on endemic flora and fauna needs to be assessed.

Arabidopsis MADS-box factor AGL16 negatively regulates drought resistance via stomatal density and stomatal movement.

Drought is one of the most important environmental factors limiting plant growth and productivity. The molecular mechanisms underlying plant drought resistance are complex and not yet fully understood. Here, we show that the Arabidopsis MADS-box transcription factor AGL16 acts as a negative regulator in drought resistance by regulating stomatal density and movement. Loss-of-AGL16 mutants were more resistant to drought stress and had higher relative water content, which was attributed to lower leaf stomatal density and more sensitive stomatal closure due to higher leaf ABA levels compared with the wild type. AGL16-overexpressing lines displayed the opposite phenotypes. AGL16 is preferentially expressed in guard cells and down-regulated in response to drought stress. The expression of CYP707A3 and AAO3 in ABA metabolism and SDD1 in stomatal development was altered in agl16 and overexpression lines, making them potential targets of AGL16. Using chromatin immunoprecipitation, transient transactivation, yeast one-hybrid, and electrophoretic mobility shift assays, we demonstrated that AGL16 was able to bind the CArG motifs in the promoters of the CYP707A3, AAO3, and SDD1 and regulate their transcription, leading to altered leaf stomatal density and ABA levels. Taking our findings together, AGL16 acts as a negative regulator of drought resistance by modulating leaf stomatal density and ABA accumulation.

Coffee plants respond to drought and elevated [CO2] through changes in stomatal function, plant hydraulic conductance, and aquaporin expression

Rising air CO2 concentration ([CO2]) is believed to mitigate the negative impacts of global climate changes such as increased air temperatures and drought events on plant growth and survival. Nonetheless, how elevated [CO2] affects the way coffee (Coffea arabica L.) plants sense and respond to drought remains a critical unknown. In this study, potted coffee plants were cultivated under two air [CO2] (ca. 400 ppm or 700 ppm) in open top chambers under greenhouse conditions. After a 5-month exposure to [CO2] treatments, plants were submitted to a progressive, controlled soil water deficit down to 20 % soil field capacity. Under well-watered (100 % field capacity) conditions, 700-plants displayed lower whole-plant transpiration rates (T) than their 400-counterparts. Changes in T were unrelated to stomatal conductances at the leaf scale (as well as stomatal morphology) or foliar ABA levels, but they were rather associated with faster stomata closure rates upon rapid increases in vapor pressure deficit in the 700-plants. During drought, 700-plants were able to maintain higher water potentials and plant hydraulic conductances for longer in parallel to higher T than their 400-counterparts. Under elevated [CO2], the faster stomatal closure rates (irrigated conditions) or the maintenance of plant hydraulic conductances (drought conditions) were associated with higher (3 to 40-fold) transcript abundance of most aquaporin genes. Altogether, our results suggest that elevated [CO2] has marked implications on how coffee plants respond to soil water deficit, ultimately permitting 700-plants to have improved fitness under drought when compared to 400-plants.

Responses of Autumn Phenology to Climate Change and the Correlations of Plant Hormone Regulation

Current understanding of autumn phenological responses to climate change in deciduous tree species remains limited, mainly due to the difficulties in defining autumn events and the lack of knowledge about its mechanism. Here we applied a method based on measuring chlorophyll A (Chla) content in leaf tissue during the entire autumn senescence processes to appropriately quantify autumn phenological processes. Beginning of leaf coloring could be defined as when about 50% of the Chl was lost. End of leaf coloring could be defined as when about 95% of the Chl was lost. Then the mechanism behind the timing of autumn senescence responses to climate change through hormone regulation was studied for the first time. Four dominate deciduous tree species with representative senescence type (Salix babylonica, Ginkgo biloba, Acer mono, Cotinus coggygria) were chosen as the subject of study. Variations in climate factors (temperature, day length, precipitation, humidity) were recorded and nine major endogenous hormones (IAA, IPA, ZR, DHZR, GA3, GA4, ABA, MeJA, BR) in leaf tissues were monitored during the entire autumn senescence processes. The experimental results verified temperature and day length are the major climate factors affecting autumn phenology. Low temperature and short day length could result in the decrease of ZR level and the increase of ABA level in leaf tissue, which directly trigger/promote senescence. Meanwhile, low temperature and short day length could cause the decrease of MeJA level and the increase of GA3 and GA4 level, which regulate the timing of autumn senescence indirectly through ZR, ABA, and IAA. Our study improves the understanding of autumn phenological response to climate change in deciduous trees.

Endogenous gibberellins and abscisic acid-metabolites: their role for during flower bud abscission and embryo development in pistachio

This study was carried out to determine the effect of different growth periods and possible role of gibberellins GAs and abscisic acid ABA metabolites the alternate bearing of the pistachio Pistacia vera L. . For this purpose, the levels of GAs and ABA in the panicles and nuts of the trees during flower bud abscission and embryo development were analyzed in the crop on year. The results showed significant differences and changes in ABA and GAs among the tissues and periods investigated. Dihydrophaseic acid DPA and GA19 were the dominant ABA and GAs in the pistachio concentrates analyzed in this work, respectively. The nut samples had higher values for almost all ABA metabolites and GAs than panicles. The ABA content of the panicles and nuts increased rapidly during flower development 35 DAFB prior to flower bud abscission while the initial decrease in the ABA content remained constant at a relatively low level at the end of June intense flower bud abscission , with the minimum levels being obtained during embryo development stage 65 DAFB . However, day 65 after full flowering, GA19 and GA44 were found to have increased. The plant growth regulator profiles of the pistachio showed delayed spikes in GA and ABA groups indicating that there is a hormone requirement during flower bud abscission and embryo development in pistachio. As a results, GA and ABA metabolites produced in different organs play an important role in the control of pistachios during embryo development and

Silicon Regulates Source to Sink Metabolic Homeostasis and Promotes Growth of Rice Plants Under Sulfur Deficiency.

Being an essential macroelement, sulfur (S) is pivotal for plant growth and development, and acute deficiency in this element leads to yield penalty. Since the last decade, strong evidence has reported the regulatory function of silicon (Si) in mitigating plant nutrient deficiency due to its significant diverse benefits on plant growth. However, the role of Si application in alleviating the negative impact of S deficiency is still obscure. In the present study, an attempt was undertaken to decipher the role of Si application on the metabolism of rice plants under S deficiency. The results showed a distinct transcriptomic and metabolic regulation in rice plants treated with Si under both short and long-term S deficiencies. The expression of Si transporters OsLsi1 and OsLsi2 was reduced under long-term deficiency, and the decrease was more pronounced when Si was provided. The expression of OsLsi6, which is involved in xylem loading of Si to shoots, was decreased under short-term S stress and remained unchanged in response to long-term stress. Moreover, the expression of S transporters OsSULTR tended to decrease by Si supply under short-term S deficiency but not under prolonged S stress. Si supply also reduced the level of almost all the metabolites in shoots of S-deficient plants, while it increased their level in the roots. The levels of stress-responsive hormones ABA, SA, and JA-lle were also decreased in shoots by Si application. Overall, our finding reveals the regulatory role of Si in modulating the metabolic homeostasis under S-deficient condition.