Roles for ALDH10 enzymes in γ-butyrobetaine synthesis, seed development, germination, and salt tolerance in Arabidopsis

Genome-Wide Identification and Expression Analysis of the Melon Aldehyde Dehydrogenase (ALDH) Gene Family in Response to Abiotic and Biotic Stresses

Through the integration of genomic information, transcriptome sequencing data, and bioinformatics methods, we conducted a comprehensive identification of the ALDH gene family in melon. We explored the impact of this gene family on melon growth, development, and their expression patterns in various tissues and under different stress conditions. Our study discovered a total of 17 ALDH genes spread across chromosomes 1, 2, 3, 4, 5, 7, 8, 11, and 12 in the melon genome. Through a phylogenetic analysis, these genes were classified into 10 distinct subfamilies. Notably, genes within the same subfamily exhibited consistent gene structures and conserved motifs. Our study discovered a pair of fragmental duplications within the melon ALDH gene. Furthermore, there was a noticeable collinearity relationship between the melon's ALDH gene and that of Arabidopsis (12 times), and rice (3 times). Transcriptome data reanalysis revealed that some ALDH genes consistently expressed highly across all tissues and developmental stages, while others were tissue- or stage-specific. We analyzed the ALDH gene's expression patterns under six stress types, namely salt, cold, waterlogged, powdery mildew, Fusarium wilt, and gummy stem blight. The results showed differential expression of CmALDH2C4 and CmALDH11A3 under all stress conditions, signifying their crucial roles in melon growth and stress response. RT-qPCR (quantitative reverse transcription PCR) analysis further corroborated these findings. This study paves the way for future genetic improvements in melon molecular breeding.

Characterization of a Drought-Induced Betaine Aldehyde Dehydrogenase Gene SgBADH from Suaeda glauca

Betaine aldehyde dehydrogenases (BADHs) are key enzymes in the biosynthesis of glycine betaine, which is an important organic osmolyte that maintains cell structure and improves plant tolerance to abiotic stresses, especially in halotolerant plants. Improving the drought tolerance of crops will greatly increase their yield. In this study, a novel BADH gene named SgBADH from Suaeda glauca was induced by drought stress or abscisic acid. To explore the biological function of SgBADH, the SgBADH gene was transformed into Arabidopsis. Then, we found SgBADH-overexpressing Arabidopsis seedlings showed enhanced tolerance to drought stress. SgBADH transgenic Arabidopsis seedlings also had longer roots compared with controls under drought stress, while SgBADH-overexpressing Arabidopsis exhibited increased glycine betaine accumulation and decreased malondialdehyde (MDA) under drought stress. Our results suggest that SgBADH might be a positive regulator in plants during the response to drought.

Proteomic analysis during seed development provides insight into the early establishment of seed dormancy in Xanthium strumarium

This experiment was carried out to provide a comprehensive insight into the protein activities involved in dormancy establishment in seeds of common cocklebur (Xanthium strumarium), an annual plant with two dimorphic seeds contained in one casing known as a burr. These consist of a smaller dormant seed and a larger non-dormant seed. The proteome profile was compared between developing dormant and non-dormant seeds of Xanthium strumarium at five consecutive stages including three, 10, 20, 30, and 45 days after burr emergence (stages 1 to 5). We identified 6524 proteins in total, and approximately 3.6% of these were differentially abundant proteins (DAPs) between the two seed types. Both seed types showed fundamental changes in developmental programs during the examined stages. More than 38% of all DAPs were observed at the first stage, supporting the importance of the early developmental stage in seed fate determination. The detected DAPs at stage 1 were mainly associated with the cell division phase, which showed a delay in the dormant seeds. Over-representation of proteins responsible for cell wall biosynthesis, cytokinesis, and seed development were detected for non-dormant seeds at the first stage, while dormancy-associated proteins showed less abundance. Stage 3 was the critical stage for switching processes toward seed maturation and abscisic acid (ABA) signaling. Interestingly, higher abundance proteins in the mature non-dormant seed were mainly involved in the facilitation of seed germination. Taken together, the temporal pattern of the accumulated proteins in developing dormant seeds demonstrated a delay in the initiation of active cell division, enriched response to ABA, and defects in seed maturation. Moreover, stored proteins in the mature dormant seed delay germination but not dormancy induction. Finally, our results suggest that dormancy may be established at a stage of seed development earlier than previously thought.

N-carboxyacyl and N-α-aminoacyl derivatives of aminoaldehydes as shared substrates of plant aldehyde dehydrogenases 10 and 7

Aldehyde dehydrogenases (ALDHs) represent a superfamily of enzymes, which oxidize aldehydes to the corresponding acids. Certain families, namely ALDH9 and ALDH10, are best active with ω-aminoaldehydes arising from the metabolism of polyamines such as 3-aminopropionaldehyde and 4-aminobutyraldehyde. Plant ALDH10s show broad specificity and accept many different aldehydes (aliphatic, aromatic and heterocyclic) as substrates. This work involved the above-mentioned aminoaldehydes acylated with dicarboxylic acids, phenylalanine, and tyrosine. The resulting products were then examined with native ALDH10 from pea and recombinant ALDH7s from pea and maize. This investigation aimed to find a common efficient substrate for the two plant ALDH families. One of the best natural substrates of ALDH7s is aminoadipic semialdehyde carrying a carboxylic group opposite the aldehyde group. The substrate properties of the new compounds were demonstrated by mass spectrometry of the reaction mixtures, spectrophotometric assays and molecular docking. The N-carboxyacyl derivatives were good substrates of pea ALDH10 but were only weakly oxidized by the two plant ALDH7s. The N-phenylalanyl and N-tyrosyl derivatives of 3-aminopropionaldehyde were good substrates of pea and maize ALDH7. Particularly the former compound was converted very efficiently (based on the kcat/Km ratio), but it was only weakly oxidized by pea ALDH10. Although no compound exhibited the same level of substrate properties for both ALDH families, we show that these enzymes may possess more common substrates than expected.

Comprehensive transcriptome and WGCNA analysis reveals the potential function of anthocyanins in low-temperature resistance of a red flower mutant tobacco

The anthocyanin is a protective substance in various plants, and plays important roles in resisting to low-temperature. Here, we explored transcriptome analysis of pink flower (as CK) and the natural mutant red flower (as research objects) under low-temperature conditions, and aimed to reveal the potential functions of anthocyanins and anthocyanin-related regulatory factors in resistance to low-temperature. Our results showed that most of the differentially expressed genes (DEGs) encoding key enzymes in the late stage of anthocyanin metabolism in the mutant were significantly up-regulated. Meanwhile, several genes significantly differentially expressed in CK or mutant were obtained by classification and analysis of transcription factors (TFs), phytohormones and osmoregulators. Additionally, WGCNA was carried out to mine hub genes resistanted to low-temperature stress in flavonoid pathway. Finally, one UFGT family gene, three MYB and one bHLH were obtained as the future hub genes of this study. Combined with the above information, we concluded that the ability of the red flower mutant to grow and develop normally at low-temperatures was the result of a combination of flavonoids and cold resistance genes.

Comparative transcriptional and co-expression network analysis of two upland cotton accessions with extreme phenotypic differences reveals molecular mechanisms of fiber development

Introduction

Upland cotton (Gossypium hirsutum) is the main source of natural fiber in the global textile industry, and thus its fiber quality and yield are important parameters. In this study, comparative transcriptomics was used to analyze differentially expressed genes (DEGs) due to its ability to effectively screen candidate genes during the developmental stages of cotton fiber. However, research using this method is limited, particularly on fiber development. The aim of this study was to uncover the molecular mechanisms underlying the whole period of fiber development and the differences in transcriptional levels.

Methods

Comparative transcriptomes are used to analyze transcriptome data and to screen for differentially expressed genes. STEM and WGCNA were used to screen for key genes involved in fiber development. qRT-PCR was performed to verify gene expression of selected DEGs and hub genes.

Results

Two accessions of upland cotton with extreme phenotypic differences, namely EZ60 and ZR014121, were used to carry out RNA sequencing (RNA-seq) on fiber samples from different fiber development stages. The results identified 704, 376, 141, 269, 761, and 586 genes that were upregulated, and 1,052, 476, 355, 259, 702, and 847 genes that were downregulated at 0, 5, 10, 15, 20, and 25 days post anthesis, respectively. Similar expression patterns of DEGs were monitored using short time-series expression miner (STEM) analysis, and associated pathways of DEGs within profiles were investigated. In addition, weighted gene co-expression network analysis (WGCNA) identified five key modules in fiber development and screened 20 hub genes involved in the development of fibers.

Discussion

Through the annotation of the genes, it was found that the excessive expression of resistance-related genes in the early fiber development stages affects the fiber yield, whereas the sustained expression of cell elongation-related genes is critical for long fibers. This study provides new information that can be used to improve fibers in newly developed upland cotton genotypes.

γ-Aminobutyrate (GABA) Regulated Plant Defense: Mechanisms and Opportunities

Global climate change and associated adverse abiotic and biotic stress conditions affect plant growth and development, and agricultural sustainability in general. Abiotic and biotic stresses reduce respiration and associated energy generation in mitochondria, resulting in the elevated production of reactive oxygen species (ROS), which are employed to transmit cellular signaling information in response to the changing conditions. Excessive ROS accumulation can contribute to cell damage and death. Production of the non-protein amino acid γ-aminobutyrate (GABA) is also stimulated, resulting in partial restoration of respiratory processes and energy production. Accumulated GABA can bind directly to the aluminum-activated malate transporter and the guard cell outward rectifying K+ channel, thereby improving drought and hypoxia tolerance, respectively. Genetic manipulation of GABA metabolism and receptors, respectively, reveal positive relationships between GABA levels and abiotic/biotic stress tolerance, and between malate efflux from the root and heavy metal tolerance. The application of exogenous GABA is associated with lower ROS levels, enhanced membrane stability, changes in the levels of non-enzymatic and enzymatic antioxidants, and crosstalk among phytohormones. Exogenous GABA may be an effective and sustainable tolerance strategy against multiple stresses under field conditions.

Recent Development on Plant Aldehyde Dehydrogenase Enzymes and Their Functions in Plant Development and Stress Signaling

Abiotic and biotic stresses induce the formation of reactive oxygen species (ROS), which subsequently causes the excessive accumulation of aldehydes in cells. Stress-derived aldehydes are commonly designated as reactive electrophile species (RES) as a result of the presence of an electrophilic α, β-unsaturated carbonyl group. Aldehyde dehydrogenases (ALDHs) are NAD(P)⁺-dependent enzymes that metabolize a wide range of endogenous and exogenous aliphatic and aromatic aldehyde molecules by oxidizing them to their corresponding carboxylic acids. The ALDH enzymes are found in nearly all organisms, and plants contain fourteen ALDH protein families. In this review, we performed a critical analysis of the research reports over the last decade on plant ALDHs. Newly discovered roles for these enzymes in metabolism, signaling and development have been highlighted and discussed. We concluded with suggestions for future investigations to exploit the potential of these enzymes in biotechnology and to improve our current knowledge about these enzymes in gene signaling and plant development.