A Linker Histone Acts as a Transcription Factor to Orchestrate Malic Acid Accumulation in Apple in Response to Sorbitol.

High carbohydrate availability promotes malic acid accumulation in fleshy fruits, but the underlying mechanism is not known. Here, we show that antisense repression of ALDOSE-6-PHOSPHATE REDUCTASE in apple (Malus domestica) decreases the concentrations of sorbitol and malate and the transcript levels of several genes involved in vacuolar malate transport, including the aluminum-activated malate transporter (ALMT) gene MdALMT9 (Ma1), the P-ATPase gene MdPH5, the MYB transcription factor gene MdMYB73, and the cold-induced basic helix-loop-helix transcription factor gene MdCIbHLH1, in fruit and leaves. We identified a linker histone H1 variant, MdH1.

The A subunit of vacuolar H-ATPase gene (CmVHA-A) plays opposite roles in plant growth and drought tolerance of chrysanthemum under different growing conditions.

As the most prominent proton pumps in plants, vacuolar H-ATPases (VHAs) comprise multiple subunits that are important for physiological processes and stress tolerance in plants. However, few studies on the roles of subunit genes of VHAs in chrysanthemum have been reported to date. In this study, the gene of A subunit of V-ATPase in chrysanthemum (CmVHA-A) was cloned and identified.

The BTB/TAZ domain-containing protein CmBT1-mediated CmANR1 ubiquitination negatively regulates root development in chrysanthemum.

Roots are fundamental for plants to adapt to variable environmental conditions. The development of a robust root system is orchestrated by numerous genetic determinants and, among them, the MADS-box gene ANR1 has garnered substantial attention. Prior research has demonstrated that, in chrysanthemum, CmANR1 positively regulates root system development.

Scaffold protein BTB/TAZ domain-containing genes (CmBTs) play a negative role in root development of chrysanthemum.

Scaffold proteins, which are known as hubs controlling information flow in cells, can function in a diverse array of biological processes in plants. The BTB/TAZ domain-containing scaffold proteins are associated with multiple signaling pathways in plants. However, there have been few studies of the roles of BT scaffold proteins in chrysanthemum to date.

Yang cycle enzyme DEP1: its moonlighting functions in PSI and ROS production during leaf senescence.

Ethylene-mediated leaf senescence and the compromise of photosynthesis are closely associated but the underlying molecular mechanism is a mystery. Here we reported that apple DEHYDRATASE-ENOLASE-PHOSPHATASE-COMPLEX1 (MdDEP1), initially characterized to its enzymatic function in the recycling of the ethylene precursor SAM, plays a role in the regulation of photosystem I (PSI) activity, activating reactive oxygen species (ROS) homeostasis, and negatively regulating the leaf senescence. A series of Y2H, Pull-down, CO-IP and Cell-free degradation biochemical assays showed that MdDEP1 directly interacts with and dephosphorylates the nucleus-encoded thylakoid protein MdY3IP1, leading to the destabilization of MdY3IP1, reduction of the PSI activity, and the overproduction of ROS in plant cells.

MdbHLH3 modulates apple soluble sugar content by activating phosphofructokinase gene expression.

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.

New insights into the role of chrysanthemum calcineurin B-like interacting protein kinase CmCIPK23 in nitrate signaling in Arabidopsis roots.

Nitrate is an important source of nitrogen and also acts as a signaling molecule to trigger numerous physiological, growth, and developmental processes throughout the life of the plant. Many nitrate transporters, transcription factors, and protein kinases participate in the regulation of nitrate signaling. Here, we identified a gene encoding the chrysanthemum calcineurin B-like interacting protein kinase CmCIPK23, which participates in nitrate signaling pathways.

Glucose sensor MdHXK1 activates an immune response to the fungal pathogen Botryosphaeria dothidea in apple.

Sugars are essential regulatory molecules involved in plant growth and development and defense response. Although the relationship between sugars and disease resistance has been widely discussed, the underlying molecular mechanisms remain unexplored. Ring rot caused by Botryosphaeria dothidea (B.

Mechanisms and regulation of organic acid accumulation in plant vacuoles.

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.

New insights into the role of MADS-box transcription factor gene CmANR1 on root and shoot development in chrysanthemum (Chrysanthemum morifolium).

Background: MADS-box transcription factors (TFs) are the key regulators of multiple developmental processes in plants; among them, a chrysanthemum MADS-box TF CmANR1 has been isolated and described as functioning in root development in response to high nitrate concentration signals. However, how CmANR1 affects root and shoot development remains unclear.

Results: We report that CmANR1 plays a positive role in root system development in chrysanthemum throughout the developmental stages of in vitro tissue cultures.

R2R3-MYB Transcription Factor MdMYB73 Confers Increased Resistance to the Fungal Pathogen in Apples the Salicylic Acid Pathway.

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 .

The apple bHLH transcription factor MdbHLH3 functions in determining the fruit carbohydrates and malate.

Changes in carbohydrates and organic acids largely determine the palatability of edible tissues of horticulture crops. Elucidating the potential molecular mechanisms involved in the change in carbohydrates and organic acids, and their temporal and spatial crosstalk are key steps in understanding fruit developmental processes. Here, we used apple (Malus domestica Borkh.

The basic helix-loop-helix transcription factor MdbHLH3 modulates leaf senescence in apple via the regulation of .

Basic helix-loop-helix (bHLH) domain-containing transcription factors are known for their roles in regulating various plant growth and developmental processes. Previously, we showed that MdbHLH3 from apple () has multiple functions, modulating both anthocyanin biosynthesis and cell acidification. Here, we show that MdbHLH3 also regulates ethylene biosynthesis and leaf senescence by promoting the expression of ().

CmTCP20 Plays a Key Role in Nitrate and Auxin Signaling-Regulated Lateral Root Development in Chrysanthemum.

Lateral root (LR) formation and development play a vital role in plant development by permitting the establishment of branched root systems. It is well known that nutrient availability controls LR development. Moreover, LR development is fine-tuned by a myriad of hormonal signals.

The MADS transcription factor CmANR1 positively modulates root system development by directly regulating in chrysanthemum.

Plant root systems are essential for many physiological processes, including water and nutrient absorption. MADS-box transcription factor (TF) genes have been characterized as the important regulators of root development in plants; however, the underlying mechanism is largely unknown, including chrysanthemum. Here, it was found that the overexpression of , a chrysanthemum MADS-box TF gene, promoted both adventitious root (AR) and lateral root (LR) development in chrysanthemum.

The regulatory module MdPUB29-MdbHLH3 connects ethylene biosynthesis with fruit quality in apple.

The plant hormone ethylene is critical for climacteric fruit ripening, while glucose and anthocyanins determine the fruit quality of climacteric fruits such as apple. Understanding the exact molecular mechanism for this process is important for elucidating the interconnection of ethylene and fruit quality. Overexpression of apple MdbHLH3 gene, an anthocyanin-related basic helix-loop-helix transcription factor (bHLH TF) gene, promotes ethylene production, and transgenic apple plantlets and trees exhibit ethylene-related root developmental abnormalities, premature leaf senescence, and fruit ripening.

Ectopic expression of the apple nucleus-encoded thylakoid protein MdY3IP1 triggers early-flowering and enhanced salt-tolerance in Arabidopsis thaliana.

Background: The roles in photosystem I (PSI) assembly of the nucleus-encoded thylakoid protein Y3IP1 who interacts with the plastid-encoded Ycf3 protein that has been well-characterized in plants. However, its function and potential mechanisms in other aspects remain poorly understood.

Results: We identified the apple MdY3IP1 gene, which encodes a protein highly homologous to the Arabidopsis Y3IP1 (AtY3IP1).

Chrysanthemum MADS-box transcription factor CmANR1 modulates lateral root development via homo-/heterodimerization to influence auxin accumulation in Arabidopsis.

Root system architecture is an important agronomic trait by which plants both acquire water and nutrients from the soil and adapt to survive in a complex environment. The adaptation of plant root systems to environmental constraints largely depends on the growth and development of lateral roots (LRs). MADS-box transcription factors (TFs) are important known regulators of plant growth, development, and response to environmental stimuli.

The R2R3-MYB transcription factor MdMYB73 is involved in malate accumulation and vacuolar acidification in apple.

Malate, the predominant organic acid in many fruits, is a crucial component of the organoleptic quality of fruit, including taste and flavor. The genetic and environmental mechanisms affecting malate metabolism in fruit cells have been studied extensively. However, the transcriptional regulation of malate-metabolizing enzymes and vacuolar transporters remains poorly understood.

Nitrate: A Crucial Signal during Lateral Roots Development.

Root plasticity is an important trait for plants to forage nutrient and adapt to survival in a complicated environment. Lateral roots (LRs) are generally more sensitive than primary roots in response to changing environmental conditions. As the main source of nitrogen for most higher plants, nitrate acting as a signal has received great attention in the regulation of LR development.

Glucose Sensor MdHXK1 Phosphorylates and Stabilizes MdbHLH3 to Promote Anthocyanin Biosynthesis in Apple.

Glucose induces anthocyanin accumulation in many plant species; however, the molecular mechanism involved in this process remains largely unknown. Here, we found that apple hexokinase MdHXK1, a glucose sensor, was involved in sensing exogenous glucose and regulating anthocyanin biosynthesis. In vitro and in vivo assays suggested that MdHXK1 interacted directly with and phosphorylated an anthocyanin-associated bHLH transcription factor (TF) MdbHLH3 at its Ser361 site in response to glucose.

MdSOS2L1 forms a complex with MdMYB1 to control vacuolar pH by transcriptionally regulating MdVHA-B1 in apples.

Vacuolar pH is important and involves in many different physiological processes in plants. A recent paper published in Plant Physiology reveals that MdMYB1 regulates vacuolar pH by directly transcriptionally regulating proton pump genes and malate transporters genes, such as V-ATPase subunit gene MdVHA-B1. Here, we found that MdSOS2L1 in vitro did not directly interact with MdMYB1, however, in vivo formed a complex with MdMYB1 in the nucleus to regulate MdVHA-B1-mediated vacuolar acidification.

MdSOS2L1 phosphorylates MdVHA-B1 to modulate malate accumulation in response to salinity in apple.

Salt-induced phosphorylation of MdVHA-B1 protein was mediated by MdSOS2L1 protein kinase, and thereby increasing malate content in apple. Salinity is an important environmental factor that influences malate accumulation in apple. However, the molecular mechanism by which salinity regulates this process is poorly understood.

MdMYB1 Regulates Anthocyanin and Malate Accumulation by Directly Facilitating Their Transport into Vacuoles in Apples.

Tonoplast transporters, including proton pumps and secondary transporters, are essential for plant cell function and for quality formation of fleshy fruits and ornamentals. Vacuolar transport of anthocyanins, malate, and other metabolites is directly or indirectly dependent on the H(+)-pumping activities of vacuolar H(+)-ATPase (VHA) and/or vacuolar H(+)-pyrophosphatase, but how these proton pumps are regulated in modulating vacuolar transport is largely unknown. Here, we report a transcription factor, MdMYB1, in apples that binds to the promoters of two genes encoding the B subunits of VHA, MdVHA-B1 and MdVHA-B2, to transcriptionally activate its expression, thereby enhancing VHA activity.