ABA Content Research Articles

Antimicrobial mechanisms of ZnO nanoparticles to phytopathogen Pseudomonas syringae: Damage of cell envelope, suppression of metabolism, biofilm and motility, and stimulation of stomatal immunity on host plant

Nanoparticles have recently been employed as a new strategy to act as bactericides in agricultural applications. However, the effects and mechanisms of foliar deposition of nanoparticles on bacterial pathogens, plant physiology and particularly plant immunity have not been sufficiently understood. Here, we investigated the effects and mechanisms of ZnO NPs in controlling of tobacco wildfire caused by Pseudomonas syringae pv. tabaci, through the comprehensive analysis of biological changes of both bacteria and plants. The global gene expression changes of Pseudomonas syringae pv. tabaci supported that the functions of “protein secretion”, “membrane part”, “signal transducer activity”, “locomotion”, “chemotaxis” and “taxis” in bacteria, as well as the metabolic pathways of “bacterial chemotaxis”, “two-component system”, “biofilm formation”, “ABC transporters” and “valine, leucine and isoleucine degradation” were significantly down-regulated by ZnO NPs. Correspondingly, we reconfirmed that the cell envelope structure, biofilm and motility of Pseudomonas syringae pv. tabaci were directly disrupted or suppressed by ZnO NPs. Different from completely killing Pseudomonas syringae pv. tabaci, ZnO NPs (0.5 mg/mL) potentially improved plant growth and immunity through enzymatic activity and global molecular response analysis. Furthermore, the changes of gene expression in ABA signaling pathway, ABA concentration and stomatal aperture all supported that ZnO NPs can specifically stimulate stomatal immunity, which is important to defend bacterial infection. Taken together, we proposed that both the inhibition or damage of motility, biofilm, metabolisms, virulence and cell envelope on P. syringae pv. tabaci, and the activation of the stomatal immunity formed two-layered antibacterial mechanisms of ZnO NPs on phytopathogenic bacteria.

Downregulation of Brassica napus MYB69 (BnMYB69) increases biomass growth and disease susceptibility via remodeling phytohormone, chlorophyll, shikimate and lignin levels.

MYB transcription factors are major actors regulating plant development and adaptability. Brassica napus is a staple oil crop and is hampered by lodging and diseases. Here, four B. napus MYB69 (BnMYB69s) genes were cloned and functionally characterized. They were dominantly expressed in stems during lignification. BnMYB69 RNA interference (BnMYB69i) plants showed considerable changes in morphology, anatomy, metabolism and gene expression. Stem diameter, leaves, roots and total biomass were distinctly larger, but plant height was significantly reduced. Contents of lignin, cellulose and protopectin in stems were significantly reduced, accompanied with decrease in bending resistance and Sclerotinia sclerotiorum resistance. Anatomical detection observed perturbation in vascular and fiber differentiation in stems, but promotion in parenchyma growth, accompanied with changes in cell size and cell number. In shoots, contents of IAA, shikimates and proanthocyanidin were reduced, while contents of ABA, BL and leaf chlorophyll were increased. qRT-PCR revealed changes in multiple pathways of primary and secondary metabolisms. IAA treatment could recover many phenotypes and metabolisms of BnMYB69i plants. However, roots showed trends opposite to shoots in most cases, and BnMYB69i phenotypes were light-sensitive. Conclusively, BnMYB69s might be light-regulated positive regulators of shikimates-related metabolisms, and exert profound influences on various internal and external plant traits.

Co-regulatory effects of hormone and mRNA-miRNA module on flower bud formation of Camellia oleifera.

Few flower buds in a high-yield year are the main factors restricting the yield of Camellia oleifera in the next year. However, there are no relevant reports on the regulation mechanism of flower bud formation. In this study, hormones, mRNAs, and miRNAs were tested during flower bud formation in MY3 ("Min Yu 3," with stable yield in different years) and QY2 ("Qian Yu 2," with less flower bud formation in a high-yield year) cultivars. The results showed that except for IAA, the hormone contents of GA3, ABA, tZ, JA, and SA in the buds were higher than those in the fruit, and the contents of all hormones in the buds were higher than those in the adjacent tissues. This excluded the effect of hormones produced from the fruit on flower bud formation. The difference in hormones showed that 21-30 April was the critical period for flower bud formation in C. oleifera; the JA content in MY3 was higher than that in QY2, but a lower concentration of GA3 contributed to the formation of the C. oleifera flower bud. JA and GA3 might have different effects on flower bud formation. Comprehensive analysis of the RNA-seq data showed that differentially expressed genes were notably enriched in hormone signal transduction and the circadian system. Flower bud formation in MY3 was induced through the plant hormone receptor TIR1 (transport inhibitor response 1) of the IAA signaling pathway, the miR535-GID1c module of the GA signaling pathway, and the miR395-JAZ module of the JA signaling pathway. In addition, the expression of core clock components GI (GIGANTEA) and CO (CONSTANS) in MY3 increased 2.3-fold and 1.8-fold over that in QY2, respectively, indicating that the circadian system also played a role in promoting flower bud formation in MY3. Finally, the hormone signaling pathway and circadian system transmitted flowering signals to the floral meristem characteristic genes LFY (LEAFY) and AP1 (APETALA 1) via FT (FLOWERING LOCUS T) and SOC1 (SUPPRESSOR OF OVEREXPRESSION OF CO 1) to regulate flower bud formation. These data will provide the basis for understanding the mechanism of flower bud alternate formation and formulating high yield regulation measures for C. oleifera.

Potato tonoplast sugar transporter 1 controls tuber sugar accumulation during postharvest cold storage.

Cold-induced sweetening (CIS), the undesirable sugar accumulation in cold-stored potato (Solanum tuberosum L.) tubers, is a severe postharvest issue in the potato processing industry. Although the process of sucrose hydrolysis by vacuolar invertase during potato CIS is well understood, there is limited knowledge about the transportation of sucrose from the cytosol to the vacuole during postharvest cold storage. Here, we report that among the three potato tonoplast sugar transporters (TSTs), StTST1 exhibits the highest expression in tubers during postharvest cold storage. Subcellular localization analysis demonstrates that StTST1 is a tonoplast-localized protein. StTST1 knockdown decreases reducing sugar accumulation in tubers during low-temperature storage. Compared to wild-type, potato chips produced from StTST1-silenced tubers displayed significantly lower acrylamide levels and lighter color after cold storage. Transcriptome analysis manifests that suppression of StTST1 promotes starch synthesis and inhibits starch degradation in cold-stored tubers. We further establish that the increased sucrose content in the StTST1-silenced tubers might cause a decrease in the ABA content, thereby inhibiting the ABA-signaling pathway. We demonstrate that the down-regulation of β-amylase StBAM1 in StTST1-silenced tubers might be directly controlled by ABA-responsive element-binding proteins (AREBs). Altogether, we have shown that StTST1 plays a critical role in sugar accumulation and starch metabolism regulation during postharvest cold storage. Thus, our findings provide a new strategy to improve the frying quality of cold-stored tubers and reduce the acrylamide content in potato chips.

Physiological and Transcriptomic Evaluation of Drought Effect on Own-Rooted and Grafted Grapevine Rootstock (1103P and 101-14MGt)

Grapevines worldwide are grafted onto Vitis spp. rootstocks in order to improve their tolerance to biotic and abiotic stresses. Thus, the response of vines to drought is the result of the interaction between the scion variety and the rootstock genotype. In this work, the responses of genotypes to drought were evaluated on 1103P and 101-14MGt plants, own-rooted and grafted with Cabernet Sauvignon, in three different water deficit conditions (80, 50, and 20% soil water content, SWC). Gas exchange parameters, stem water potential, root and leaf ABA content, and root and leaf transcriptomic response were investigated. Under well-watered conditions, gas exchange and stem water potential were mainly affected by the grafting condition, whereas under sever water deficit they were affected by the rootstock genotype. Under severe stress conditions (20% SWC), 1103P showed an "avoidance" behavior. It reduced stomatal conductance, inhibited photosynthesis, increased ABA content in the roots, and closed the stomata. The 101-14MGt maintained a high photosynthetic rate, limiting the reduction of soil water potential. This behavior results in a "tolerance" strategy. An analysis of the transcriptome showed that most of the differentially expressed genes were detected at 20% SWC, and more significantly in roots than in leaves. A core set of genes has been highlighted on the roots as being related to the root response to drought that are not affected by genotype nor grafting. Genes specifically regulated by grafting and genes specifically regulated by genotype under drought conditions have been identified as well. The 1103P, more than the 101-14MGt, regulated a high number of genes in both own-rooted and grafted conditions. This different regulation revealed that 1103P rootstock readily perceived the water scarcity and rapidly faced the stress, in agreement with its avoidance strategy.

Knockdown of Sly-miR164a Enhanced Plant Salt Tolerance and Improved Preharvest and Postharvest Fruit Nutrition of Tomato

Salinity stress is a serious limitation to tomato growth and development. The aim of this study was to investigate the effects of Sly-miR164a on tomato growth and fruit nutritional quality under salt stress. The results showed that the root length, fresh weight, plant height, stem diameter and ABA content of miR164a#STTM (knockdown of Sly-miR164a) lines were higher than those of WT and miR164a#OE (overexpression of Sly-miR164a) lines under salt stress. Compared with WT, miR164a#STTM tomato lines exhibited lower ROS accumulation under salt stress. In addition, the fruits of miR164a#STTM tomato lines had higher soluble solids, lycopene, ascorbic acid (ASA) and carotenoid content compared with WT. The study indicated that tomato plants were more sensitive to salt when Sly-miR164a was overexpressed, while knockdown of Sly-miR164a enhanced plant salt tolerance and improved fruit nutritional value.

Stem girdling enhances ABA-induced stomatal closure of phosphorus-deprived soybean plants

To investigate whether shoot-to-root communication modulates physiological (leaf water relations and growth), phytohormonal and transcriptomic responses to phosphorus (P) deprivation, soybean (Glycine max L. Merr.) plants received a factorial combination of low P conditions and girdling. Stem phloem tissue was surgically excised from the first internode between the cotyledonary and the first unifoliate leaf, immediately before imposing different P treatments (250 and 5 μM P in hydroponics). Root and leaf expression of genes involved in P homeostasis, sucrose metabolism and transporters, starch metabolism, hormone homeostasis and ABA signalling were analysed, to determine their regulation and relationships to tissue P / ABA concentrations. P deprivation mainly upregulated root and leaf P homeostasis gene expression only in intact plants, acting to maintain foliar P homeostasis. Although girdling suppressed root expression of these genes, it increased root P concentrations and decreased leaf P concentrations. Initially, P deprivation decreased stomatal conductance before leaf water status decreased, irrespective of girdling. Later, stomatal closure of girdled P-deprived plants was greater than intact P-deprived plants at the same, lower leaf water status, coincident with enhanced foliar ABA accumulation and expression of ABA biosynthesis genes. In contrast, P deprivation decreased foliar concentrations of the antitranspirant jasmonic acid and increased root and leaf SA concentrations at the end of the experiment. P deprivation also decreased foliar cytokinin and gibberellin concentrations before leaf growth was inhibited and leaf water status declined, suggesting non-hydraulic growth regulation. Girdling and P deprivation increased foliar sucrose and hexoses, corresponding to increased sucrose invertase and transporter gene expression in the leaves, while decreasing root sucrose and hexoses concentrations and downregulating sucrose metabolism but increasing transporter gene expression. Girdling perturbs multiple root and shoot phytohormonal responses that modulate physiological adaptation to P deprivation.

Regulation of carotenoid and flavonoid biosynthetic pathways in Lactuca sativa var capitate L. in protected cultivation.

In the face of a growing world population and limited land, there is an urgent demand for higher productivity of food crops, and cultivation systems must be adapted to future needs. Sustainable crop production should aim for not only high yields, but also high nutritional values. In particular, the consumption of bioactive compounds such as carotenoids and flavonoids is associated with a reduced incidence of non-transmissible diseases. Modulating environmental conditions by improving cultivation systems can lead to the adaption of plant metabolisms and the accumulation of bioactive compounds. The present study investigates the regulation of carotenoid and flavonoid metabolisms in lettuce (Lactuca sativa var capitate L.) grown in a protected environment (polytunnels) compared to plants grown without polytunnels. Carotenoid, flavonoid and phytohormone (ABA) contents were determined using HPLC-MS and transcript levels of key metabolic genes were analyzed by RT-qPCR. In this study, we observed inverse contents of flavonoids and carotenoids in lettuce grown without or under polytunnels. Flavonoid contents on a total and individual level were significantly lower, while total carotenoid content was higher in lettuce plants grown under polytunnels compared to without. However, the adaptation was specific to the level of individual carotenoids. For instance, the accumulation of the main carotenoids lutein and neoxanthin was induced while the β-carotene content remained unchanged. In addition, our findings suggest that the flavonoid content of lettuce depends on transcript levels of the key biosynthetic enzyme, which is modulated by UV light. A regulatory influence can be assumed based on the relation between the concentration of the phytohormone ABA and the flavonoid content in lettuce. In contrast, the carotenoid content is not reflected in transcript levels of the key enzyme of either the biosynthetic or the degradation pathway. Nevertheless, the carotenoid metabolic flux determined using norflurazon was higher in lettuce grown under polytunnels, suggesting posttranscriptional regulation of carotenoid accumulation, which should be an integral part of future studies. Therefore, a balance needs to be found between the individual environmental factors, including light and temperature, in order to optimize the carotenoid or flavonoid contents and to obtain nutritionally highly valuable crops in protected cultivation.

Paclobutrazol Promotes Root Development of Difficult-to-Root Plants by Coordinating Auxin and Abscisic Acid Signaling Pathways in Phoebe bournei.

Phoebe bournei is a rare and endangered plant endemic to China with higher-value uses in essential oil and structural wood production. Its seedlings are prone to death because of its undeveloped system. Paclobutrazol (PBZ) can improve root growth and development in certain plants, but its concentration effect and molecular mechanism remain unclear. Here, we studied the physiological and molecular mechanisms by which PBZ regulates root growth under different treatments. We found that, with moderate concentration treatment (MT), PBZ significantly increased the total root length (69.90%), root surface area (56.35%), and lateral root number (47.17%). IAA content was the highest at MT and was 3.83, 1.86, and 2.47 times greater than the control, low, and high-concentration treatments. In comparison, ABA content was the lowest and reduced by 63.89%, 30.84%, and 44.79%, respectively. The number of upregulated differentially expressed genes (DEGs) induced at MT was more than that of down-regulated DEGs, which enriched 8022 DEGs in response to PBZ treatments. WGCNA showed that PBZ-responsive genes were significantly correlated with plant hormone content and involved in plant hormone signal transduction and MAPK signal pathway-plant pathways, which controls root growth. The hub genes are observably associated with auxin, abscisic acid syntheses, and signaling pathways, such as PINs, ABCBs, TARs, ARFs, LBDs, and PYLs. We constructed a model which showed PBZ treatments mediated the antagonism interaction of IAA and ABA to regulate the root growth in P. bournei. Our result provides new insights and molecular strategies for solving rare plants' root growth problems.

High temperature inhibited the accumulation of anthocyanin by promoting ABA catabolism in sweet cherry fruits.

Color is an essential appearance characteristic of sweet cherry (Prunus avium L.) fruits and mainly determined by anthocyanin. Temperature plays an important role in the regulation of anthocyanin accumulation. In this research, anthocyanin, sugar, plant hormone and related gene expression were analyzed using physiological and transcriptomic methods in order to reveal the effects of high temperature on fruit coloring and the related mechanism. The results showed that high temperature severely inhibited anthocyanin accumulation in fruit peel and slowed the coloring process. The total anthocyanin content in fruit peel increasedby 455% and 84% after 4 days of normal temperature treatment (NT, 24°C day/14°C night) and high temperature treatment (HT, 34°C day/24°C night), respectively. Similarly, the contents of 8 anthocyanin monomers were significantly higher in NT than in HT. HT also affected the levels of sugars and plant hormones. The total soluble sugar content increased by 29.49% and 16.81% in NT and HT, respectively, after 4 days of treatment. The levels of ABA, IAA and GA20 also increased in both the two treatments but more slowly in HT. Conversely, the contents of cZ, cZR and JA decreased more rapidly in HT than in NT. The results of the correlation analysis showed that the ABA and GA20 contents were significantly correlated with the total anthocyanin contents. Further transcriptome analysis showed that HT inhibited the activation of structural genes in anthocyanin biosynthesis as well as the repression of CYP707A and AOG, which dominated the catabolism and inactivation of ABA. These results indicate that ABA may be a key regulator in the high-temperature-inhibited fruit coloring of sweet cherry. High temperature induces higher ABA catabolism and inactivation, leading to lower ABA levels and finally resulting in slow coloring.

SbNAC9 Improves Drought Tolerance by Enhancing Scavenging Ability of Reactive Oxygen Species and Activating Stress-Responsive Genes of Sorghum.

Drought stress severely threatens the yield of cereal crops. Therefore, understanding the molecular mechanism of drought stress response of plants is crucial for developing drought-tolerant cultivars. NAC transcription factors (TFs) play important roles in abiotic stress of plants, but the functions of NAC TFs in sorghum are largely unknown. Here, we characterized a sorghum NAC gene, SbNAC9, and found that SbNAC9 can be highly induced by polyethylene glycol (PEG)-simulated dehydration treatments. We therefore investigated the function of SbNAC9 in drought stress response. Sorghum seedlings overexpressing SbNAC9 showed enhanced drought-stress tolerance with higher chlorophyll content and photochemical efficiency of PSII, stronger root systems, and higher reactive oxygen species (ROS) scavenging capability than wild-type. In contrast, sorghum seedlings with silenced SbNAC9 by virus-induced gene silencing (VIGS) showed weakened drought stress tolerance. Furthermore, SbNAC9 can directly activate a putative peroxidase gene SbC5YQ75 and a putative ABA biosynthesis gene SbNCED3. Silencing SbC5YQ75 and SbNCED3 led to compromised drought tolerance and reduced ABA content of sorghum seedlings, respectively. Therefore, our findings revealed the important role of SbNAC9 in response to drought stress in sorghum and may shed light on genetic improvement of other crop species under drought-stress conditions.

Effects of cadmium on transcription, physiology, and ultrastructure of two tobacco cultivars

Cadmium (Cd) is one of the most toxic heavy metal pollutants worldwide. Tobacco is an important cash crop; however, the accumulation of Cd in its biomass is very high. Cadmium may enter the body of smokers with contaminated tobacco and the surrounding environment via smoke. Therefore, it is important to understand the mechanisms of Cd accumulation and tolerance in tobacco plants, especially in the leaves. In this study, the effects of Cd on the growth, accumulation, and biochemical indices of two tobacco varieties, K326 (Cd resistant) and NC55 (Cd sensitive), were studied through transcriptomic and physiological experiments. Transcriptome and physiological analyses showed differences in the expression of Cd transport and Cd resistance related genes between NC55 and K326 under Cd stress. The root meristem cells of NC55 were more severely damaged. The antioxidant enzyme activity, ABA and ZT content, chlorophyll content, photosynthetic rate, and nitrogen metabolism enzyme activity in K326 leaves were higher than in NC55. These data elucidate the mechanisms of low Cd accumulation and high Cd tolerance in K326 leaves and provide a theoretical basis for cultivating tobacco varieties with low Cd accumulation and high Cd resistance.

NAC domain transcription factor gene GhNAC3 confers drought tolerance in plants

Abiotic stress seriously affects the growth, yield, and fiber quality of cotton. It is of great importance to cultivate drought-resistant and salt-tolerant cotton. NAC (NAM, ATAF1/2, and CUC2) is a plant-specific transcription factor, which is widely involved in the response to abiotic stress. Here, we discovered the GhNAC3 gene isolated from the expression profile of drought stress in cotton and verified its functions in cotton. First, GhNAC3 was strongly induced expression by drought and salt stresses. Gene structure analysis revealed that GhNAC3 had a conserved NAC domain and was homologous to several stress-related NAC transcription factors gene of Arabidopsis. Subcellular localization and transcriptional activation assays revealed that GhNAC3 was a nuclear protein with a C-terminal transcriptional activation domain. Overexpression of GhNAC3 enhanced Arabidopsis tolerance to drought stress with reduced sensitivity to ABA, characterized by increased germination and cotyledon rates under drought stress, and promoted root elongation. VIGS silencing of GhNAC3 reduced cotton tolerance to drought stress as indicated by the low water content of the leaves under drought treatment, significantly faster water loss and lower ABA content in detached leaves, along with the accumulation of more hydrogen peroxide (H2O2) and malondialdehyde (MDA). In conclusion, GhNAC3 plays an important role in the abiotic stress of cotton, which might have great application potential in molecular breeding of cotton varieties with drought resistance.

Effect of Rhizophagus intraradices on growth of Salvia miltiorrhiza

The study aimed to explore the effects of inoculation of Rhizophagus intraradices on the biomass, effective component content, and endogenous hormone content of Salvia miltiorrhiza through pot experiments. The number of leaves, plant height, dry weight of aboveground and underground parts, branch number, root number, root length, root diameter, and other biomass were mea-sured by weighing and counting methods. The content of salvianolic acid B, caffeic acid, rosmarinic acid, tanshinone Ⅰ, tanshinone Ⅱ_A, cryptotanshinone, and other effective components was determined by ultra-high performance liquid chromatography. The content of ABA and GA_3 was determined by triple quadrupole mass spectrometry. The correlations between biomass and effective components and between effective components and plant hormones ABA and GA_3 were analyzed. The results showed that R. intraradices significan-tly increased the aboveground dry weight, leaf number, and root number of S. miltiorrhiza by 0.24-0.65 times, respectively. The content of salvianolic acid B and rosmarinic acid in the aboveground part and the content of salvianolic acid B, caffeic acid, rosmarinic acid, tanshinone Ⅰ, and tanshinone Ⅱ_A in the underground part were significantly increased by 0.44-1.78 times, respectively. R. intraradices infection significantly increased the GA_3/ABA values of aboveground and underground parts by 3.82 and 76.47 times, respectively. The correlation analysis showed that caffeic acid, the effective component of the aboveground part, was significantly positively correlated with plant height, tanshinone Ⅱ_A, the effective component of the underground part, was significantly positively correlated with biomass root number, cryptotanshinone, and dry weight, while rosmarinic acid was significantly negatively correlated with dry weight. There were significant positive correlations between cryptotanshinone and ABA, tanshinone Ⅱ_A and ABA and GA_3, and caffeic acid and GA_3. In conclusion, R. intraradices can promote the accumulation of biomass and secondary metabolites of S. miltiorrhiza and regulate the balance between plant hormones ABA and GA_3, thereby promoting the growth of S. miltiorrhiza.

Integrated analysis of transcriptome, small RNA, and phytohormonal content changes between <i>Artemisia annua</i> Linn. and <i>Nicotiana benthamiana</i> Domin in heterogeneous grafting

Grafting, one of the most artificial propagation methods of plants, now is widely used in flower breeding, vegetable cultivation and stress response research. In order to discover the reason for success of heterograft and information exchange mechanisms, we used <italic>Artemisia annua</italic> (Aa) as scion and <italic>Nicotiana benthamiana</italic> (Nb) as rootstock to build a grafting model. After grafting 30 days co-growth, 7,794 DEGs (different expression genes) and 8,214 DEGs were identified in Aa scion and Nb rootstock, respectively. Most of the DEGs belong to defense response and signal transduction in scion and substance metabolism in rootstock, which indicate that the diverging response mechansim of grafted parts. Besides, 50 Nb genes and 20 Aa genes were detected in Aa scion and Nb rootstock, which were regarded as potentially active genes during graft process. The most abundant miRNAs are <italic>miR159</italic> and <italic>miR166</italic>, which may be closely related to their conservation and physiological functions. Besides, <italic>miR159</italic> and <italic>miR166</italic> could quickly respond to internal change, therefore the two miRNAs should be considered as biomarker of successful grafting models. And then, as simultaneously screened miRNAs, <italic>miR396</italic> and <italic>miR6149</italic> could be potential biomarker in Aa and Nb, respectively<italic>.</italic> Through the analysis of miRNA-target gene network in differentially expressed miRNAs, transcription factor R2R3-MYB, <italic>bHLH</italic>, <italic>GRAS</italic>, <italic>GAMYB</italic>, <italic>SBP-box</italic>, <italic>MADS-box</italic>, <italic>IIS</italic> in scion and <italic>NF</italic>-<italic>Y</italic> in rootstock were regarded as key genes involved in growth and development of grafted plants. The content of ABA, JA, CK was calculated in grafted plants and showed its respective functions.

Integrated transcriptome and metabolome analysis unveiled the mechanisms of xenia effect and the role of different pollens on aroma formation in ‘Yali’ pear (Pyrus bretschneideri Rehd)

• ‘Hongnanguo’ pollinizer has a xenia effect on ‘Yali’ pear fruits aroma quality. • 189 DAMs and 12,032 DEGs were identified. • ‘Hongnanguo’ pollinizer increased the content of ABA, IAA, and ethylene. • Established a possible regulatory network of the mechanism of xenia effect on pear aroma formation. The flavor of ‘Yali’ pear fruits has substantially declined recently as a result of poor pollination tree selection. Xenia effect is a powerful mechanism for regulating aroma production. To study the effect of different pollens on aroma quality and the molecular basis of xenia effect in ‘Yali’ pear fruits, ‘Hongnanguo’ and ‘Xuehuali’ were used as pollinizers, and the hybrid fruits were named YH and YX, respectively. Metabolome, transcriptome, volatile compounds, and hormone were jointly analyzed in YH and YX peels with three ripening stages. After pollinating with ‘Hongnanguo’ pollen, the contents of total aroma, esters and nerolidol, the odor activity value of characteristic volatiles in YH were significantly increased, compared with the aroma character of the pollinizer cultivars, indicating ‘Hongnanguo’ pollinizer has a xenia effect on ‘Yali’ pear fruits aroma quality. Further, the content of ABA, IAA, and ethylene reveal the differences during aroma formation between YH and YX. 189 differentially accumulated metabolites (DAMs) and 12,032 differentially expressed genes (DEGs) were identified. Based on co-expression network analysis, network maps of ‘Yali’ pear aroma-related DEGs were generated. We surmise aroma biosynthesis genes ( ADH, ALDH, NES , and FPS ), ABA, IAA, ethylene signal transduction, and several transcription factors play important roles in the xenia effect.

The identification of suitable internal reference genes in quinoa seeds subjected to abscisic acid and gibberellin treatment

Abstract: Quinoa has been recognized as the sole “comprehensive nutritional crop”; however, it is susceptible to pre-harvest sprouting (PHS). While quantitative reverse transcription polymerase chain reaction (RT-qPCR) has been extensively employed for gene expression level detection, the selection of suitable reference genes is imperative to ensure precise gene expression quantification across diverse conditions. This study aims to identify stable reference genes in quinoa seeds under ABA and GA, in order to provide a basis for subsequent research on PHS. Seeds were subjected to different concentrations of ABA and GA (10 μM, 50 μM, 100 μM, and 200 μM). The most suitable treatment concentration was determined based on seed viability. Here, MON1, GAPDH, EIF3, EF1α, ACT, TUB1, and TUB6 were selected as candidate genes. The suitability of these reference genes under different conditions was assessed using various methods including Ct values, geNorm, NormFinder, BestKeeper, Delta Ct, and RefFinder. Based on the results obtained from the hormone experiments, it was observed that the application of 100 μM ABA and 200 μM GA yielded the most advantageous outcomes. Additionally, the most appropriate reference genes for different treatments are ACT and TUB1 (H2O treatment), EIF3 and MON1 (ABA, GA treatment and also for the combined data set of the three groups). However, GAPDH exhibited the least stability across all treatments. In summary, ACT is recommended as the reference gene for natural quinoa germination, while EIF3 and MON1 should be used for ABA and GA treatments.

Transcriptome and co-expression network analysis uncover the key genes mediated by endogenous defense hormones in tea plant in response to the infestation of &lt;i&gt;Empoasca onukii&lt;/i&gt; Matsuda

The tea green leafhopper [<italic>Empoasca</italic> (<italic>Matsumurasca</italic>) <italic>onukii</italic> Matsuda] is one of the most dominant pests in the tea production regions of China, greatly impacting tea yield and quality. Extensive studies have attributed the plant defense response to pest infestation to the activation of hormone signals, but the role of defense hormones in tea plants in response to the feeding of <italic>E. onukii</italic> is not clear. RNA-seq was performed on the leaf samples collected at different time points (6, 24 and 48 h) after feeding with <italic>E. onukii</italic> to explore the transcription characteristics of tea plant responses to feeding. The content variation characteristics of four phytohormones (JA, JA-Ile, ABA and SA) during this process were also determined. The results showed that feeding elevated the expression of key genes involved in phenylpropanoid biosynthesis, flavonoid biosynthesis, α-linolenic acid metabolism and terpenoids synthesis pathways, especially in the early stage after feeding. The contents of JA, JA-Ile, and ABA dramatically increased at different time points after feeding, but the absolute content decreased over time. The change in the absolute content of SA was opposite to that of the above three hormones. Two gene co-expression networks that were significantly positively associated with these hormonal changes were constructed based on WGCNA. The screened hub genes provide useful genetic resources for exploring the hormone-mediated defense responses of tea plants against <italic>E. onukii</italic>. Our results lay the foundation for the ecological control of <italic>E. onukii</italic> and breeding of resistant tea plant cultivars.

MpSNAC67 transcription factor of banana regulates stress induced senescence through salicylic acid dependent pathway

Stress induced senescence negatively impact yield but is a crucial factor for reproductive growth and thus ensues the evolutionary success of crops. Senescence associated NAC transcription factors have been reported to control ABA-mediated senescence however, their regulation over salicylic acid (SA) mediated senescence has not been studied. Here, we report the functions of MpSNAC67 , a NAC transcription factor from banana in regulating the stress induced senescence through coordination of senescence associated genes and SA content. MpSNAC67 induces ICS1 while it suppresses SAGT1 causing reduced SA content in snac67 plants which suggest that MpSNAC67 functions through SA mediated pathways. Suppression of NCED -like and ABA3 -like in SNAC67-Oxp plants and reduced ABA content in snac67 knockout plants suggest that MpSNAC67 functions through ABA independent pathways. ROS accumulation, a function of SA-pathway was significantly diminished in snac67 plants as evident by induction of antioxidant genes in snac67 plants and suppression in SNAC67- Oxp plants. MpSNAC67 induces SA mediated senescence as evident by elevated chlorophyll-content and suppression of senescence associated genes such as ORS1 -like in snac67 plants. ORS1 -like is strongly induced under natural senescence while MpSNAC67 is not suggesting that MpSNAC67 coordinate stress-specific senescence to age dependent senescence. MpSNAC67 is induced under salinity stress, drought and exposure of SA, ABA and methyl-jasmonate suggesting MpSNAC67 coordinate different stress signals to finetune SA-mediated senescence in plants. Thus, MpSNAC67 is master regulator of stress mediated senescence in banana plants. • MpSNAC67 regulates stress induced senescence through elevation of SA content. • MpSNAC67 is induced under salinity, drought, exposure of SA, ABA and methyl-jasmonate indicating roles of MpSNAC67 in regulating different stress induced senescence in plants. • ORS1 -like but not MpSNAC67 is strongly induced under aging associated senescence indicating that MpSNAC67 coordinate stress induced senescence to age dependent senescence. • ROS level were significantly diminished in snac67 plants indicating that MpSNAC67 triggers SA dependent ROS generation during senescence.

Effect of abscisic acid concentrations and stages of spray on maize growth, seed yield and germination at late planting

A field experiment was carried out in Al-Hajjaj district- Salah Al-Din Governorate, during the autumn season of 2021. The experimental design was randomized complete block design (RCBD) in three replications. It had three ABA concentrations of 0, 9 and 12 mg L-1 that sprayed on plants at 4 and 8 leaves and at the beginning of flowering. Results indicated that a concentration of 12 mg L-1 was superior in shortening the number of days from sowing until 50% of tasseling (male flowering) 38.33 days and silking (female flowering) 41 days. The same concentration recorded the highest stem diameter of 2.47 cm, seeds number per ear 682.89 seed ear-1, 1000 seed weight 373.77 g, single plant yield 165.64 g and seed yield 11.04 tons ha-1, protein content 9.80% and ash percentage 1.39%. However, control recorded the highest germination percentage and speed of 95.89 and 64.80, respectively. Spraying ABA at 4 leaves was superior in recording the least number of days from planting until 50% of tasseling 38.50 days and silking 43.55 days and also excelled in giving the highest stem diameter 2.35 cm. However, foliar application of ABA at the beginning of flowering showed the highest means of number of seeds per ear 664.99 seed ear-1, 1000 seed weight 361.80 g, single plant yield 158.70 g, seed yield 10.57 tons ha-1, protein percentage 10.03%, and ash percentage 1.36%. Hence, foliar spray at 4 leaves recorded the highest mean 84.81 of germination speed.