Summary
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.
See also the Commentary on this article by Martinoia & Neuhaus, 239: 821–823.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Sugars are involved in plant growth, fruit quality, and signaling perception. Therefore, understanding the mechanisms involved in soluble sugar accumulation is essential to understand fruit ...development. Here, we report that MdPFPβ, a pyrophosphate‐dependent phosphofructokinase gene, regulates soluble sugar accumulation by enhancing the photosynthetic performance and sugar‐metabolizing enzyme activities in apple (Malus domestica Borkh.). Biochemical analysis revealed that a basic helix‐loop‐helix (bHLH) transcription factor, MdbHLH3, binds to the MdPFPβ promoter and activates its expression, thus promoting soluble sugar accumulation in apple fruit. In addition, MdPFPβ overexpression in tomato influenced photosynthesis and carbon metabolism in the plant. Furthermore, we determined that MdbHLH3 increases photosynthetic rates and soluble sugar accumulation in apple by activating MdPFPβ expression. Our results thus shed light on the mechanism of soluble sugar accumulation in apple leaves and fruit: MdbHLH3 regulates soluble sugar accumulation by activating MdPFPβ gene expression and coordinating carbohydrate allocation.
In apple leaves and fruits, the basic helix‐loop‐helix transcription factor MdbHLH3 regulates sugar accumulation by activating expression of the pyrophosphate‐dependent phosphofructokinase gene MdPFPβ and coordinating carbohydrate allocation.
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FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Abstract
In fleshy fruits, organic acids are the main source of fruit acidity and play an important role in regulating osmotic pressure, pH homeostasis, stress resistance, and fruit quality. The ...transport of organic acids from the cytosol to the vacuole and their storage are complex processes. A large number of transporters carry organic acids from the cytosol to the vacuole with the assistance of various proton pumps and enzymes. However, much remains to be explored regarding the vacuolar transport mechanism of organic acids as well as the substances involved and their association. In this review, recent advances in the vacuolar transport mechanism of organic acids in plants are summarized from the perspectives of transporters, channels, proton pumps, and upstream regulators to better understand the complex regulatory networks involved in fruit acid formation.
Application of a molecular catalyst in artificial photosynthesis is confronted with challenges such as rapid deactivation due to photodegradation or detrimental aggregation in harsh conditions. In ...this work, a metal–organic cage Pd6(RuL3)828+ (MOC-16), characteristic of a photochemical molecular device (PMD) concurrently integrating eight Ru2+ light-harvesting centers and six Pd2+ catalytic centers for efficient homogeneous H2 production, is successfully heterogenized through incorporation into a metal–organic framework (MOF) of ZIF-8 and then transformed into a carbonate matrix of Zn x (MeIm) x (CO3) x (CZIF), leading to hybridized MOC-16@CZIF. This MOC@MOF integrated photocatalyst inherits a highly efficient and directional electron transfer in the picosecond domain of MOC-16 and possesses one order increased microsecond magnitude of the triplet excited-state electron in comparison to that of the primitive MOC-16. The carbonate CZIF matrix endows MOC-16@CZIF with water wettability, serving as a proton relay to facilitate proton delivery by virtue of H2O as proton carriers. Electron transfer during the photocatalytic process is also enhanced by infiltration of a sacrificial agent of BIH into the CZIF matrix to promote conductivity, owing to its strong reducing ability to induce free charge carriers. These synergistic effects contribute to the extra high activity for H2 generation, making the turnover frequency of this heterogeneous MOC-16@CZIF photocatalyst maintain a level of ∼0.4 H2·s–1, increased by 50-fold over that of a homogeneous PMD. Meanwhile, it is robust enough to tolerate harsh reaction conditions, presenting an unprecedented heterogenization example of homogeneous PMD with a MOF-derived matrix to mimic catalytic features of a natural photosystem, which may shed light on the design of multifunctional PMD@MOF materials to expand the number of molecular catalysts for practical application in artificial photosynthesis.
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IJS, KILJ, NUK, PNG, UL, UM
•The research advance on anthocyanins of horticultural products.•We summarize the anthocyanin biosynthetic pathways and transport mechanisms in horticultural plants.•We summarize the environmental ...factors affecting anthocyanin accumulation in this review.
Anthocyanins, a flavonoid group of polyphenolic compounds, are important human health-promoting pigments responsible for the red and blue colors of horticultural products such as fruits, flowers, and leaves. The anthocyanin biosynthetic and transport pathways are well known. Key regulatory factors involved in these pathways have been characterized in many plant species. Recently, it has been found that regulatory proteins controlling anthocyanin biosynthesis at the transcriptional and post-transcriptional levels are found to be differentially modulated by environmental and biological factors such as light, temperature, sugars, and hormones. In this review, a simplified model for the role of environmental and developmental factors in the modulation of the anthocyanin biosynthesis pathway in horticultural plants is proposed, with emphasis on the coordinated regulation of the key transcriptional MYB-bHLH-WD40 (MBW) complex.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Anthocyanins have essential biological functions, affecting the development of horticultural production. They are synthesized in the cytoplasm through flavonoid metabolic pathways and finally ...transported into vacuoles for storage. Plant glutathione S-transferases (GSTs) are multifunctional enzymes involved in anthocyanin transportation. In this study, we identified 38 GSTs from the apple (
) genome (HFTH1 Whole Genome v1.0) based on the sequence similarity with the GST family proteins of
. These
genes could be grouped into nine chief subclasses: U, F, L, Z, T, GHR, EF1Bγ, TCHQD, and DHAR. The structures, motifs, three-dimensional models, and chromosomal distribution of
genes were further analyzed. Elements which are responsive for some hormones and stress, and others that involve genes related to flavonoid biosynthesis were forecast in the promoter of
. In addition, we identified 32 orthologous gene pairs between apple and
. These genes indicated that numerous apple and
counterparts appeared to be derived from a common ancestor. Amongst the 38
genes,
was considerably correlated with anthocyanin variation in terms of extracting expression profiles from reported. Finally, further functional identification in apple transgenic calli and subcellular localization confirmed that
was of great significance in anthocyanin accumulation in apple.
Main conclusion
MdPRX34L
enhanced resistance to
Botryosphaeria dothidea
by increasing salicylic acid (SA) and abscisic acid (ABA) content as well as the expression of related defense genes
.
The ...class III peroxidase (PRX) multigene family is involved in complex biological processes. However, the molecular mechanism of PRXs in the pathogen defense of plants against
Botryosphaeria dothidea
(
B. dothidea
) remains unclear. Here, we cloned the PRX gene
MdPRX34L
, which was identified as a positive regulator of the defense response to
B. dothidea
, from the apple cultivar 'Royal Gala.' Overexpression of
MdPRX34L
in apple calli decreased sensitivity to salicylic acid (SA) and abscisic acid（ABA). Subsequently, overexpression of
MdPRX34L
in apple calli increased resistance to
B. dothidea
infection. In addition, SA contents and the expression levels of genes related to SA synthesis and signaling in apple calli overexpressing
MdPRX34L
were higher than those in the control after inoculation, suggesting that
MdPRX34L
enhances resistance to
B. dothidea
via the SA pathway. Interestingly, infections in apple calli by
B. dothidea
caused an increase in endogenous levels of ABA followed by induction of ABA-related genes expression. These findings suggest a potential mechanism by which
MdPRX34L
enhances plant–pathogen defense against
B. dothidea
by regulating the SA and ABA pathways.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Various abiotic stressors, particularly drought stress, affect plant growth and yield. Zinc finger proteins play an important role in plant abiotic stress tolerance. Here, we isolated the apple ...MdZAT10 gene, a C2H2-type zinc finger protein, which is a homolog of Arabidopsis STZ/ZAT10. MdZAT10 was localized to the nucleus and highly expressed in leaves and fruit. Promoter analysis showed that MdZAT10 contained several response elements and the transcription level of MdZAT10 was induced by abiotic stress and hormone treatments. MdZAT10 was responsive to drought treatment both at the transcriptional and post-translational levels. MdZAT10-overexpressing apple calli decreased the expression level of MdAPX2 and increased sensitivity to PEG 6000 treatment. Moreover, ectopically expressed MdZAT10 in Arabidopsis reduced the tolerance to drought stress, and exhibited higher water loss, higher malondialdehyde (MDA) content and higher reactive oxygen species (ROS) accumulation under drought stress. In addition, MdZAT10 reduced the sensitivity to abscisic acid in apple. Ectopically expressed MdZAT10 in Arabidopsis promoted seed germination and seedling growth. These results indicate that MdZAT10 plays a negative regulator in the drought resistance, which can provide theoretical basis for further molecular mechanism research.
•MdZAT10 reduced the drought tolerance by regulating the expression of MdAPX2 and increased ROS accumulation in apple.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Abstract
Apple ring rot is a severe disease that affects the yield and quality of apple fruits worldwide. However, the underlying molecular mechanism that involved in this process still remains ...largely unexplored. Here, we report that apple POZ/BTB CONTAINING-PROTEIN 1 (MdPOB1), a BTB-BACK domain E3 ligase protein, functions to suppress apple pathogen defense against Botryosphaeria dothidea (B. dothidea). Both in vitro and in vivo assays indicated that MdPOB1 interacted directly with and degraded apple U-box E3 ligase MdPUB29, a well-established positive regulator of plant innate immunity, through the ubiquitin/26S proteasome pathway. A series of transgenic analyses in apple fruits demonstrated that MdPOB1 affected apple pathogen defense against B. dothidea at least partially, if not completely, via regulating MdPUB29. Additionally, it was found that the apple pathogen defense against B. dothidea was correlated with the H2O2 contents and the relative expression of salicylic acid (SA) synthesis- and SA signaling-related genes, which might be regulated via degradation of MdPUB29 by MdPOB1. Overall, our findings provide new insights into the mechanism of the MdPOB1 modulation of apple ring rot resistance, which occur by directly regulating potential downstream target protein MdPUB29 for proteasomal degradation in apple.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
MYB transcription factors (TFs) participate in many biological processes. However, the molecular mechanisms by which MYB TFs affect plant resistance to apple ring rot remain poorly understood. Here, ...the R2R3-MYB gene
was cloned from "
" apples and functionally characterized as a positive regulator of the defense response to
. qRT-PCR and GUS staining demonstrated that
was strongly induced in apple fruits and transgenic calli after inoculation with
.
overexpression improved resistance to
in apple calli and fruits, while
suppression weakened. Increased resistance to
was also observed in
-expressing
. Interestingly, salicylic acid (SA) contents and the expression levels of genes related with SA synthesis and signaling were greater in
-overexpressing plant materials compared to wild-type controls after inoculation, suggesting that MdMYB73 might enhance resistance to
the SA pathway. Finally, we discovered that MdMYB73 interacts with MdWRKY31, a positive regulator of
. Together, MdWRKY31 and MdMYB73 enhanced
resistance in apples. Our results clarify the mechanisms by which MdMYB73 improves resistance to
and suggest that resistance may be affected by regulating the SA pathway.
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IJS, KILJ, NUK, PNG, UL, UM, UPUK
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