ABSTRACT
The pH of the solution in the rhizosphere is an important factor that determines the availability and mobility of nutrients for plant uptake. Solution pH may also affect the root distribution and architecture of apple rootstocks. In this study, we evaluated the effect of solution pH on root system development of apple rootstocks using an aeroponics system designed and developed at Cornell AgriTech Geneva, USA. Four Geneva® apple rootstocks (G.210, G.214, G.41, and G.890) were grown in an aeroponic system under nutrient solution misting featuring continuously adjusted pH levels to three pH treatments (5.5, 6.5, and 8.0). Root development was monitored for 30 days and evaluated regularly for distribution and root mass. Images of the developed roots grown in the aeroponic system were collected at the end of the experiment using a high-resolution camera and analyzed using GiA Roots® software, which generates root architecture parameter values in a semi-automated fashion. The resulting root architecture analysis showed that the Geneva® rootstocks were significantly different for two architecture parameters. The length-to-width ratio analysis represented by two GiA Roots parameters (minor-to-major ellipse ratio and network width-to-depth ratio) showed that G.210 was flatter than G.890, which had a greater tendency to grow downward. Rootstocks G.214 and G.41 displayed similar growth values. The solution pH affected most root architecture parameter measurements where overall root growth was higher at pH 8 than at pH 5.5 and 6.5, which showed similar growth. In general, the average root width tended to decrease at higher pH values. While there were no significant differences in the leaf nutrient concentrations of P, K, Ca, Mg, S, B, Zn, Cu, and Fe within the four rootstocks, the pH level of the solution had a significant effect on P, Ca, and Mn. This study is the first of its kind to investigate the effect of pH on root architecture in a soil-free (aeroponic) environment and may have implications for apple root behavior under field conditions where pH levels are different.
ABSTRACT
MYB transcription factors have been linked to anthocyanin synthesis and various color phenotypes in plants. In apple, MYB10 confers a red-flesh phenotype due to a minisatellite insertion in its R6 promoter, but R6:MYB10 genotypes exhibit various degrees of red pigmentation in the flesh, suggesting the involvement of other genetic factors. Here, it is shown that MdWRKY10, a transcription factor identified via DNA pull-down trapping, binds to the promoter of MdMYB10 and activates its transcription. MdWRKY10 specifically interacts with the WDR protein MdTTG1 to join the apple MYB-bHLH-WDR (MBW) complex, which significantly enhances its transcriptional activation activity. A 163-bp InDel detected in the promoter region of the alleles of MdWRKY10 in a hybrid population of identical heterozygous genotypes regarding R6 by structural variation analysis, contains a typical W-box element that MdWRKY10 binds to for transactivation. This leads to increased transcript levels of MdWRKY10 and MdMYB10 and enhanced anthocyanin synthesis in the flesh, largely accounting for the various degrees of flesh red pigmentation in the R6 background. These findings reveal a novel regulatory role of the WRKY-containing protein complex in the formation of red flesh apple phenotypes and provide broader insights into the molecular mechanism governing anthocyanin synthesis in plants.
Subject(s)
Gene Expression Regulation, Plant , Malus , Phenotype , Pigmentation , Plant Proteins , Promoter Regions, Genetic , Transcription Factors , Promoter Regions, Genetic/genetics , Pigmentation/genetics , Malus/genetics , Malus/metabolism , Transcription Factors/genetics , Transcription Factors/metabolism , Gene Expression Regulation, Plant/genetics , Plant Proteins/genetics , Plant Proteins/metabolism , INDEL Mutation/genetics , Anthocyanins/genetics , Anthocyanins/metabolism , Genotype , Fruit/genetics , Fruit/metabolismABSTRACT
The architecture of apple trees plays a pivotal role in shaping their growth and fruit-bearing potential, forming the foundation for precision apple management. Traditionally, 2D imaging technologies were employed to delineate the architectural traits of apple trees, but their accuracy was hampered by occlusion and perspective ambiguities. This study aimed to surmount these constraints by devising a 3D geometry-based processing pipeline for apple tree structure segmentation and architectural trait characterization, utilizing point clouds collected by a terrestrial laser scanner (TLS). The pipeline consisted of four modules: (a) data preprocessing module, (b) tree instance segmentation module, (c) tree structure segmentation module, and (d) architectural trait extraction module. The developed pipeline was used to analyze 84 trees of two representative apple cultivars, characterizing architectural traits such as tree height, trunk diameter, branch count, branch diameter, and branch angle. Experimental results indicated that the established pipeline attained an R2 of 0.92 and 0.83, and a mean absolute error (MAE) of 6.1 cm and 4.71 mm for tree height and trunk diameter at the tree level, respectively. Additionally, at the branch level, it achieved an R2 of 0.77 and 0.69, and a MAE of 6.86 mm and 7.48° for branch diameter and angle, respectively. The accurate measurement of these architectural traits can enable precision management in high-density apple orchards and bolster phenotyping endeavors in breeding programs. Moreover, bottlenecks of 3D tree characterization in general were comprehensively analyzed to reveal future development.
ABSTRACT
Vacuolar malic acid accumulation largely determines fruit acidity, a key trait for the taste and flavor of apple and other fleshy fruits. Aluminum-activated malate transporter 9 (ALMT9/Ma1) underlies a major genetic locus, Ma, for fruit acidity in apple, but how the protein transports malate across the tonoplast is unclear. Here, it is shown that overexpression of the coding sequence of Ma1 (Ma1α) drastically decreases fruit acidity in "Royal Gala" apple, leading to uncovering alternative splicing underpins Ma1's function. Alternative splicing generates two isoforms: Ma1ß is 68 amino acids shorter with much lower expression than the full-length protein Ma1α. Ma1ß does not transport malate itself but interacts with the functional Ma1α to form heterodimers, creating synergy with Ma1α for malate transport in a threshold manner (When Ma1ß/Ma1α ≥ 1/8). Overexpression of Ma1α triggers feedback inhibition on the native Ma1 expression via transcription factor MYB73, decreasing the Ma1ß level well below the threshold that leads to significant reductions in Ma1 function and malic acid accumulation in fruit. Overexpression of Ma1α and Ma1ß or genomic Ma1 increases both isoforms proportionally and enhances fruit malic acid accumulation. These findings reveal an essential role of alternative splicing in ALMT9-mediated malate transport underlying apple fruit acidity.
Subject(s)
Alternative Splicing , Malates , Malus , Malates/metabolism , Alternative Splicing/genetics , Malus/genetics , Malus/metabolism , Fruit/metabolism , Fruit/genetics , Plant Proteins/metabolism , Plant Proteins/genetics , Vacuoles/metabolism , Vacuoles/genetics , Gene Expression Regulation, Plant/geneticsABSTRACT
Carotenoids are essential for photosynthesis and photoprotection. Plants must evolve multifaceted regulatory mechanisms to control carotenoid biosynthesis. However, the regulatory mechanisms and the regulators conserved among plant species remain elusive. Phytoene synthase (PSY) catalyzes the highly regulated step of carotenogenesis and geranylgeranyl diphosphate synthase (GGPPS) acts as a hub to interact with GGPP-utilizing enzymes for the synthesis of specific downstream isoprenoids. Here, we report a function of Nudix hydrolase 23 (NUDX23), a Nudix domain-containing protein, in post-translational regulation of PSY and GGPPS for carotenoid biosynthesis. NUDX23 expresses highly in Arabidopsis (Arabidopsis thaliana) leaves. Overexpression of NUDX23 significantly increases PSY and GGPPS protein levels and carotenoid production, whereas knockout of NUDX23 dramatically reduces their abundances and carotenoid accumulation in Arabidopsis. NUDX23 regulates carotenoid biosynthesis via direct interactions with PSY and GGPPS in chloroplasts, which enhances PSY and GGPPS protein stability in a large PSY-GGPPS enzyme complex. NUDX23 was found to co-migrate with PSY and GGPPS proteins and to be required for the enzyme complex assembly. Our findings uncover a regulatory mechanism underlying carotenoid biosynthesis in plants and offer promising genetic tools for developing carotenoid-enriched food crops.
Subject(s)
Arabidopsis Proteins , Arabidopsis , Carotenoids , Gene Expression Regulation, Plant , Carotenoids/metabolism , Arabidopsis/genetics , Arabidopsis/metabolism , Arabidopsis Proteins/metabolism , Arabidopsis Proteins/genetics , Nudix Hydrolases , Chloroplasts/metabolism , Geranylgeranyl-Diphosphate Geranylgeranyltransferase/metabolism , Geranylgeranyl-Diphosphate Geranylgeranyltransferase/genetics , Farnesyltranstransferase/metabolism , Farnesyltranstransferase/genetics , Pyrophosphatases/metabolism , Pyrophosphatases/genetics , Protein Processing, Post-Translational , Plants, Genetically Modified , Plant Leaves/metabolism , Plant Leaves/geneticsABSTRACT
Chromoplasts are plant organelles with a unique ability to sequester and store massive carotenoids. Chromoplasts have been hypothesized to enable high levels of carotenoid accumulation due to enhanced sequestration ability or sequestration substructure formation. However, the regulators that control the substructure component accumulation and substructure formation in chromoplasts remain unknown. In melon (Cucumis melo) fruit, ß-carotene accumulation in chromoplasts is governed by ORANGE (OR), a key regulator for carotenoid accumulation in chromoplasts. By using comparative proteomic analysis of a high ß-carotene melon variety and its isogenic line low-ß mutant that is defective in CmOr with impaired chromoplast formation, we identified carotenoid sequestration protein FIBRILLIN1 (CmFBN1) as differentially expressed. CmFBN1 expresses highly in melon fruit tissue. Overexpression of CmFBN1 in transgenic Arabidopsis (Arabidopsis thaliana) containing ORHis that genetically mimics CmOr significantly enhances carotenoid accumulation, demonstrating its involvement in CmOR-induced carotenoid accumulation. Both in vitro and in vivo evidence showed that CmOR physically interacts with CmFBN1. Such an interaction occurs in plastoglobules and results in promoting CmFBN1 accumulation. CmOR greatly stabilizes CmFBN1, which stimulates plastoglobule proliferation and subsequently carotenoid accumulation in chromoplasts. Our findings show that CmOR directly regulates CmFBN1 protein levels and suggest a fundamental role of CmFBN1 in facilitating plastoglobule proliferation for carotenoid sequestration. This study also reveals an important genetic tool to further enhance OR-induced carotenoid accumulation in chromoplasts in crops.
Subject(s)
Arabidopsis , Cucurbitaceae , beta Carotene/metabolism , Cucurbitaceae/metabolism , Fibrillins/metabolism , Proteomics , Carotenoids/metabolism , Plastids/metabolism , Arabidopsis/genetics , Arabidopsis/metabolism , Fruit/geneticsABSTRACT
The weather variations around the world are already having a profound impact on agricultural production. This impacts apple production and the quality of the product. Through agricultural precision, growers attempt to optimize both yield and fruit size and quality. Two experiments were conducted using field-grown "Gala" apple trees in Geneva, NY, USA, in 2021 and 2022. Mature apple trees (Malus × domestica Borkh. cv. Ultima "Gala") grafted onto G.11 rootstock planted in 2015 were used for the experiment. Our goal was to establish a relationship between stem water potential (Ψtrunk), which was continuously measured using microtensiometers, and the growth rate of apple fruits, measured continuously using dendrometers throughout the growing season. The second objective was to develop thresholds for Ψtrunk to determine when to irrigate apple trees. The economic impacts of different irrigation regimes were evaluated. Three different water regimes were compared (full irrigation, rainfed and rain exclusion to induce water stress). Trees subjected the rain-exclusion treatment were not irrigated during the whole season, except in the spring (April and May; 126 mm in 2021 and 100 mm in 2022); that is, these trees did not receive water during June, July, August and half of September. Trees subjected to the rainfed treatment received only rainwater (515 mm in 2021 and 382 mm in 2022). The fully irrigated trees received rain but were also irrigated by drip irrigation (515 mm in 2021 and 565 mm in 2022). Moreover, all trees received the same amount of water out of season in autumn and winter (245 mm in 2021 and 283 mm in 2022). The microtensiometer sensors detected differences in Ψtrunk among our treatments over the entire growing season. In both years, experimental trees with the same trunk cross-section area (TCSA) were selected (23-25 cm-2 TCSA), and crop load was adjusted to 7 fruits·cm-2 TCSA in 2021 and 8.5 fruits·cm-2 TCSA in 2022. However, the irrigated trees showed the highest fruit growth rates and final fruit weight (157 g and 70 mm), followed by the rainfed only treatment (132 g and 66 mm), while the rain-exclusion treatment had the lowest fruit growth rate and final fruit size (107 g and 61 mm). The hourly fruit shrinking and swelling rate (mm·h-1) measured with dendrometers and the hourly Ψtrunk (bar) measured with microtensiometers were correlated. We developed a logistic model to correlate Ψtrunk and fruit growth rate (g·h-1), which suggested a critical value of -9.7 bars for Ψtrunk, above which there were no negative effects on fruit growth rate due to water stress in the relatively humid conditions of New York State. A support vector machine model and a multiple regression model were developed to predict daytime hourly Ψtrunk with radiation and VPD as input variables. Yield and fruit size were converted to crop value, which showed that managing water stress with irrigation during dry periods improved crop value in the humid climate of New York State.
ABSTRACT
Sorbitol is a major photosynthate produced in leaves and transported through the phloem of apple (Malus domestica) and other tree fruits in Rosaceae. Sorbitol stimulates its own metabolism, but the underlying molecular mechanism remains unknown. Here, we show that sucrose nonfermenting 1 (SNF1)-related protein kinase 1 (SnRK1) is involved in regulating the sorbitol-responsive expression of both SORBITOL DEHYDROGENASE 1 (SDH1) and ALDOSE-6-PHOSPHATE REDUCTASE (A6PR), encoding 2 key enzymes in sorbitol metabolism. SnRK1 expression is increased by feeding of exogenous sorbitol but decreased by sucrose. SnRK1 interacts with and phosphorylates the basic leucine zipper (bZIP) transcription factor bZIP39. bZIP39 binds to the promoters of both SDH1 and A6PR and activates their expression. Overexpression of SnRK1 in 'Royal Gala' apple increases its protein level and activity, upregulating transcript levels of both SDH1 and A6PR without altering the expression of bZIP39. Of all the sugars tested, sorbitol is the only 1 that stimulates SDH1 and A6PR expression, and this stimulation is blocked by RNA interference (RNAi)-induced repression of either SnRK1 or bZIP39. These findings reveal that sorbitol acts as a signal regulating its own metabolism via SnRK1-mediated phosphorylation of bZIP39, which integrates sorbitol signaling into the SnRK1-mediated sugar signaling network to modulate plant carbohydrate metabolism.
Subject(s)
Malus , Malus/metabolism , Phosphorylation , Transcription Factors/metabolism , Carbohydrate Metabolism/genetics , Sorbitol/pharmacology , Sorbitol/metabolism , Sucrose/metabolism , Gene Expression Regulation, PlantABSTRACT
Malic acid accumulation in the vacuole largely determines acidity and perception of sweetness of apple. It has long been observed that reduction in malate level is associated with increase in ethylene production during the ripening process of climacteric fruits, but the molecular mechanism linking ethylene to malate reduction is unclear. Here, we show that ethylene-modulated WRKY transcription factor 31 (WRKY31)-Ethylene Response Factor 72 (ERF72)-ALUMINUM ACTIVATED MALATE TRANSPORTER 9 (Ma1) network regulates malate accumulation in apple fruit. ERF72 binds to the promoter of ALMT9, a key tonoplast transporter for malate accumulation of apple, transcriptionally repressing ALMT9 expression in response to ethylene. WRKY31 interacts with ERF72, suppressing its transcriptional inhibition activity on ALMT9. In addition, WRKY31 directly binds to the promoters of ERF72 and ALMT9, transcriptionally repressing and activating ERF72 and ALMT9, respectively. The expression of WRKY31 decreases in response to ethylene, lowering the transcription of ALMT9 directly and via its interactions with ERF72. These findings reveal that the regulatory complex WRKY31 forms with ERF72 responds to ethylene, linking the ethylene signal to ALMT9 expression in reducing malate transport into the vacuole during fruit ripening.
Subject(s)
Malus , Malus/genetics , Malus/metabolism , Malates/metabolism , Aluminum/metabolism , Fruit/genetics , Fruit/metabolism , Ethylenes/metabolism , Gene Expression Regulation, Plant , Plant Proteins/genetics , Plant Proteins/metabolismSubject(s)
Malus , Malus/genetics , Gene Editing , Proteins/genetics , Plant Growth Regulators , Regeneration/genetics , Plant Shoots/geneticsABSTRACT
The photoprotective role of anthocyanin remains controversial. In this study, we explored the effects of anthocyanin on photosynthesis and photoprotection using transgenic 'Galaxy Gala' apple plants overexpressing MdMYB10 under high light stress. The overexpression of MdMYB10 dramatically enhanced leaf anthocyanin accumulation, allowing more visible light to be absorbed, particularly in the green region. However, through post-transcriptional regulation, anthocyanin accumulation lowered leaf photosynthesis in both photochemical reaction and CO2 fixation capacities. Anthocyanin accumulation also led to a decreased de-epoxidation state of the xanthophyll cycle and antioxidant capacities, but this is most likely a response to the light-shielding effect of anthocyanin, as indicated by a higher chlorophyll concentration and lower chlorophyll a/b ratio. Under laboratory conditions when detached leaves lost carbon fixation capacity due to the limitation of CO2 supply, the photoinhibition of detached transgenic red leaves was less severe under strong white, green, or blue light, but it became more severe in response to strong red light compared with that of the wild type. In field conditions when photosynthesis was performed normally in both green and transgenic red leaves, the degree of photoinhibition was comparable between transgenic red leaves and wild type leaves, but it was less severe in transgenic young shoot bark compared with the wild type. Taken together, these data show that anthocyanin protects plants from high light stress by absorbing excessive visible light despite reducing photosynthesis.
Subject(s)
Fabaceae , Malus , Anthocyanins/metabolism , Chlorophyll A , Malus/genetics , Malus/metabolism , Antioxidants/metabolism , Carbon Dioxide , Photosynthesis/physiology , Chlorophyll , Plant Leaves/metabolism , Light , Plants, Genetically Modified/genetics , Plants, Genetically Modified/metabolism , Fabaceae/metabolism , Xanthophylls/metabolismABSTRACT
Organic acid content in fruit is an important determinant of peach organoleptic quality, which undergoes considerable variations during development and maturation. However, its molecular mechanism remains largely unclear. In this study, an integrative approach of genome-wide association studies and comparative transcriptome analysis were applied to identify candidate genes involved in organic acid accumulation in peach. A key gene PpTST1, encoding tonoplast sugar transporter, was identified and the genotype of PpTST1 with a single-base transversion (G1584T) in the third exon which leads to a single amino acid substitution (Q528H) was associated with low level of organic acid content in peach. Overexpression of PpTST1His resulted in reduced organic acid content along with increased sugar content both in peach and tomato fruits, suggesting its dual function in sugar accumulation and organic acid content reduction. Two V-type proton ATPases interact with PpTST1 in yeast two-hybridization assay. In addition, the G1584T transversion appeared and gradually accumulated during domestication and improvement, which indicated that PpTST1 was under selection. The identification and characterization of PpTST1 would facilitate the improvement of peach fruit quality.
ABSTRACT
Primary metabolism provides energy for growth and development as well as secondary metabolites for diverse environmental responses. Here we describe an unexpected consequence of disruption of a glycolytic enzyme enolase named LOW EXPRESSION OF OSMOTICALLY RESPONSIVE GENE 2 (LOS2) in causing constitutive defense responses or autoimmunity in Arabidopsis thaliana. The autoimmunity in the los2 mutant is accompanied by a higher expression of about one-quarter of intracellular immune receptor nucleotide-binding leucine-rich repeat (NLR) genes in the genome and is partially dependent on one of these NLR genes. The LOS2 gene was hypothesized to produce an alternatively translated protein c-Myc Binding Protein (MBP-1) that functions as a transcriptional repressor. Complementation tests show that LOS2 executes its function in growth and immunity regulation through the canonical enolase activity but not the production of MBP-1. In addition, the autoimmunity in the los2 mutants leads to a higher accumulation of sugars and organic acids and a depletion of glycolytic metabolites. These findings indicate that LOS2 does not exert its function in immune responses through an alternatively translated protein MBP-1. Rather, they show that a perturbation of glycolysis from the reduction of the enolase activity results in activation of NLR-involved immune responses which further influences primary metabolism and plant growth, highlighting the complex interaction between primary metabolism and plant immunity.
Subject(s)
Arabidopsis Proteins , Arabidopsis , Arabidopsis/metabolism , Arabidopsis Proteins/genetics , Arabidopsis Proteins/metabolism , Gene Expression Regulation, Plant/genetics , Glycolysis/genetics , Phosphopyruvate Hydratase/genetics , Phosphopyruvate Hydratase/metabolism , Plant Immunity/geneticsABSTRACT
Domestication of the apple was mainly driven by interspecific hybridization. In the present study, we report the haplotype-resolved genomes of the cultivated apple (Malus domestica cv. Gala) and its two major wild progenitors, M. sieversii and M. sylvestris. Substantial variations are identified between the two haplotypes of each genome. Inference of genome ancestry identifies ~23% of the Gala genome as of hybrid origin. Deep sequencing of 91 accessions identifies selective sweeps in cultivated apples that originated from either of the two progenitors and are associated with important domestication traits. Construction and analyses of apple pan-genomes uncover thousands of new genes, with hundreds of them being selected from one of the progenitors and largely fixed in cultivated apples, revealing that introgression of new genes/alleles is a hallmark of apple domestication through hybridization. Finally, transcriptome profiles of Gala fruits at 13 developmental stages unravel ~19% of genes displaying allele-specific expression, including many associated with fruit quality.
Subject(s)
Domestication , Hybridization, Genetic/genetics , Malus/classification , Malus/genetics , Evolution, Molecular , Fruit/genetics , Genome, Plant/geneticsABSTRACT
A Rosaceae family-level candidate gene approach was used to identify genes associated with sugar content in blackberry (Rubus subgenus Rubus). Three regions conserved among apple (Malus × domestica), peach (Prunus persica), and alpine strawberry (Fragaria vesca) were identified that contained previously detected sweetness-related quantitative trait loci (QTL) in at least two of the crops. Sugar related genes from these conserved regions and 789 sugar-associated apple genes were used to identify 279 Rubus candidate transcripts. A Hyb-Seq approach was used in conjunction with PacBio sequencing to generate haplotype level sequence information of sugar-related genes for 40 cultivars with high and low soluble solids content from the University of Arkansas and USDA blackberry breeding programs. Polymorphisms were identified relative to the 'Hillquist' blackberry (R. argutus) and ORUS 4115-3 black raspberry (R. occidentalis) genomes and tested for their association with soluble solids content (SSC). A total of 173 alleles were identified that were significantly (α = 0.05) associated with SSC. KASP genotyping was conducted for 92 of these alleles on a validation set of blackberries from each breeding program and 48 markers were identified that were significantly associated with SSC. One QTL, qSSC-Ruh-ch1.1, identified in both breeding programs accounted for an increase of 1.5 °Brix and the polymorphisms were detected in the intron space of a sucrose synthase gene. This discovery represents the first environmentally stable sweetness QTL identified in blackberry. The approach demonstrated in this study can be used to develop breeding tools for other crops that have not yet benefited directly from the genomics revolution.
Subject(s)
Fragaria , Malus , Rosaceae , Rubus , DNA , Fragaria/genetics , Fruit , Malus/genetics , Plant Breeding , Rosaceae/genetics , Rubus/geneticsABSTRACT
The fermentation of apple juice into hard cider is a complex biochemical process that transforms sugars into alcohols by yeast, of which Saccharomyces cerevisiae is the most widely used species. Among many factors, hydrogen sulfide (H2S) production by yeast during cider fermentation is affected by yeast strain and yeast assimilable nitrogen (YAN) concentration in the apple juice. In this study, we investigated the regulatory mechanism of YAN concentration on S. cerevisiae H2S formation. Two S. cerevisiae strains, UCD522 (a H2S-producing strain) and UCD932 (a non-H2S-producing strain), were used to ferment apple juice that had Low, Intermediate, and High diammonium phosphate (DAP) supplementation. Cider samples were collected 24 and 72 h after yeast inoculation. Using RNA-Seq, differentially expressed genes (DEGs) identification and annotation, Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment, we found that gene expression was dependent on yeast strain, fermentation duration, H2S formation, and the interaction of these three factors. For UCD522, under the three DAP treatments, a total of 30 specific GO terms were identified. Of the 18 identified KEGG pathways, "Sulfur metabolism," "Glycine, serine and threonine metabolism," and "Biosynthesis of amino acids" were significantly enriched. Both GO and KEGG analyses revealed that the "Sulfate Reduction Sequence (SRS) pathway" was significantly enriched. We also found a complex relationship between H2S production and stress response genes. For UCD522, we confirm that there is a non-linear relationship between YAN and H2S production, with the Low and Intermediate treatments having greater H2S production than the High treatment. By integrating results obtained through the transcriptomic analysis with yeast physiological data, we present a mechanistic view into the H2S production by yeast as a result of different concentrations of YAN during cider fermentation.
ABSTRACT
Climate-driven phenological change across local spatial gradients leads to leaf shape variation. At higher elevations, leaves of broadleaf species tend to become narrower, but the underlying molecular mechanism is largely unknown. In this study, a series of morphometric analyses and biochemical assays, combined with functional identification in apple, were performed. We show that the decrease in apple leaf width with increasing altitude is controlled by a basic/helix-loop-helix transcription factor (bHLH TF), MdbHLH3. The MdbHLH3-overexpressing lines have a lower transcript abundance of MdPIN1 encoding an auxin efflux carrier but a higher transcript abundance of MdGH3-2 encoding a putative auxin amido conjugate synthase, resulting in a lower free auxin concentration; feeding the transgenic leaves with exogenous auxin partially restores leaf width. MdbHLH3 transcriptionally suppresses and activates MdPIN1 and MdGH3-2, respectively, by specifically binding to their promoters. This alters auxin homeostasis and transport, consequently leading to changes in leaf shape. These findings suggest that the bHLH TF MdbHLH3 directly modulates auxin signaling in controlling leaf shape in response to local spatial gradients in apple.
Subject(s)
Malus , Basic Helix-Loop-Helix Transcription Factors/genetics , Basic Helix-Loop-Helix Transcription Factors/metabolism , Gene Expression Regulation, Plant , Indoleacetic Acids , Malus/genetics , Malus/metabolism , Plant Leaves/metabolism , Plant Proteins/genetics , Plant Proteins/metabolismABSTRACT
Excessive application of nitrate, an essential macronutrient and a signal regulating diverse physiological processes, decreases malate accumulation in apple (Malus domestica) fruit, but the underlying mechanism remains poorly understood. Here, we show that an apple BTB/TAZ protein, MdBT2, is involved in regulating malate accumulation and vacuolar pH in response to nitrate. In vitro and in vivo assays indicate that MdBT2 interacts directly with and ubiquitinates a bHLH transcription factor, MdCIbHLH1, via the ubiquitin/26S proteasome pathway in response to nitrate. This ubiquitination results in the degradation of MdCIbHLH1 protein and reduces the transcription of MdCIbHLH1-targeted genes involved in malate accumulation and vacuolar acidification, including MdVHA-A, which encodes a vacuolar H+-ATPase, and MdVHP1, which encodes a vacuolar H+-pyrophosphatase, as well as MdALMT9, which encodes an aluminum-activated malate transporter. A series of transgenic analyses in apple materials including fruits, plantlets, and calli demonstrate that MdBT2 controls nitrate-mediated malate accumulation and vacuolar pH at least partially, if not completely, via regulating the MdCIbHLH1 protein level. Taken together, these findings reveal that MdBT2 regulates the stability of MdCIbHLH1 via ubiquitination in response to nitrate, which in succession transcriptionally reduces the expression of malate-associated genes, thereby controlling malate accumulation and vacuolar acidification in apples under high nitrate supply.
Subject(s)
Malates/metabolism , Nitrates/pharmacology , Plant Proteins/metabolism , Plants, Genetically Modified/metabolism , Gene Expression Regulation, Plant/drug effects , Gene Expression Regulation, Plant/genetics , Inorganic Pyrophosphatase/genetics , Inorganic Pyrophosphatase/metabolism , Plant Proteins/genetics , Plants, Genetically Modified/drug effects , Plants, Genetically Modified/genetics , Protein Binding/drug effects , Protein Binding/genetics , Ubiquitination/drug effects , Ubiquitination/genetics , Vacuolar Proton-Translocating ATPases/metabolismABSTRACT
Rapid pollen tube growth requires uptake of Suc or its hydrolytic products, hexoses, from the apoplast of surrounding tissues in the style. Due to species-specific sugar requirements, reliance of pollen germination and tube growth on cell wall invertase and Suc or hexose transporters varies between species, but it is not known if plants have a sugar transporter that mediates the uptake of both hexose and Suc for pollen tube growth. Here, we show that a sugar transporter protein in apple (Malus domestica), MdSTP13a, takes up both hexose and Suc when expressed in yeast, and is essential for pollen tube growth on Glc and Suc but not on maltose. MdSTP13a-mediated direct uptake of Suc is primarily responsible for apple pollen tube growth on Suc medium. Sorbitol, a major photosynthate and transport carbohydrate in apple, modulates pollen tube growth via the MYB transcription factor MdMYB39L, which binds to the promoter of MdSTP13a to activate its expression. Antisense repression of MdSTP13a blocks sorbitol-modulated pollen tube growth. These findings demonstrate that MdSTP13a takes up both hexose and Suc for sorbitol-modulated pollen tube growth in apple, revealing a situation where acquisition of sugars for pollen tube growth is regulated by a sugar alcohol.