Overexpression of the Aldehyde Dehydrogenase Gene ZmALDH Confers Aluminum Tolerance in Arabidopsis thaliana

Transcriptomic and metabolomic insights into the antimony stress response of tall fescue (Festuca arundinacea)

Antimony (Sb) is a toxic heavy metal that severely inhibits plant growth and development and threatens human health. Tall fescue, one of the most widely used grasses, has been reported to tolerate heavy metal stress. However, the adaptive mechanisms of Sb stress in tall fescue remain largely unknown. In this study, transcriptomic and metabolomic techniques were applied to elucidate the molecular mechanism of the Sb stress response in tall fescue. These results showed that the defense process in tall fescue was rapidly triggered during the early stages of Sb stress. Sb stress had toxic effects on tall fescue, and the cell wall and voltage-gated channels are crucial for regulating Sb permeation into the cells. In addition, the pathway of glycine, serine and threonine metabolism may play key roles in the Sb stress response of tall fescue. Genes such as ALDH7A1 and AGXT2 and metabolites such as aspartic acid, pyruvic acid, and biuret, which are related to biological processes and pathways, were key genes and compounds in the Sb stress response of tall fescue. Therefore, the regulatory mechanisms of specific genes and pathways should be investigated further to improve Sb stress tolerance.

Effects of Cadmium Stress on Tartary Buckwheat Seedlings

Cadmium (Cd) is a naturally occurring toxic heavy metal that adversely affects plant germination, growth, and development. While the effects of Cd have been described on many crop species including rice, maize, wheat and barley, few studies are available on cadmium's effect on Tartary buckwheat which is a traditional grain in China. We examined nine genotypes and found that 30 µM of Cd reduced the root length in seedlings by between 4 and 44% and decreased the total biomass by 7 to 31%, compared with Cd-free controls. We identified a significant genotypic variation in sensitivity to Cd stress. Cd treatment decreased the total root length and the emergence and growth of lateral roots, and these changes were significantly greater in the Cd-sensitive genotypes than in tolerant genotypes. Cd resulted in greater wilting and discoloration in sensitive genotypes than in tolerant genotypes and caused more damage to the structure of root and leaf cells. Cd accumulated in the roots and shoots, but the concentrations in the sensitive genotypes were significantly greater than in the more tolerant genotypes. Cd treatment affected nutrient uptake, and the changes in the sensitive genotypes were greater than those in the tolerant genotypes, which could maintain their concentrations closer to the control levels. The induction of SOD, POD, and CAT activities in the roots and shoots was significantly greater in the tolerant genotypes than in the sensitive genotypes. We demonstrated that Cd stress reduced root and shoot growth, decreased plant biomass, disrupted nutrient uptake, altered cell structure, and managed Cd-induced oxidative stress differently in the sensitive and tolerant genotypes of Tartary buckwheat.

Physiological and proteomic characterization revealed the response mechanisms underlying aluminium tolerance in lentil (Lens culinaris Medikus)

Aluminium (Al) toxicity causes major plant distress, affecting root growth, nutrient uptake and, ultimately, agricultural productivity. Lentil, which is a cheap source of vegetarian protein, is recognized to be sensitive to Al toxicity. Therefore, it is important to dissect the physiological and molecular mechanisms of Al tolerance in lentil. To understand the physiological system and proteome composition underlying Al tolerance, two genotypes [L-4602 (Al-tolerant) and BM-4 (Al-sensitive)] were studied at the seedling stage. L-4602 maintained a significantly higher root tolerance index and malate secretion with reduced Al accumulation than BM-4. Also, label-free proteomic analysis using ultra-performance liquid chromatography-tandem mass spectrometer exhibited significant regulation of Al-responsive proteins associated with antioxidants, signal transduction, calcium homeostasis, and regulation of glycolysis in L-4602 as compared to BM-4. Functional annotation suggested that transporter proteins (transmembrane protein, adenosine triphosphate-binding cassette transport-related protein and multi drug resistance protein), antioxidants associated proteins (nicotinamide adenine dinucleotide dependent oxidoreductase, oxidoreductase molybdopterin binding protein & peroxidases), kinases (calmodulin-domain kinase & protein kinase), and carbohydrate metabolism associated proteins (dihydrolipoamide acetyltransferase) were found to be abundant in tolerant genotype providing protection against Al toxicity. Overall, the root proteome uncovered in this study at seedling stage, along with the physiological parameters measured, allow a greater understanding of Al tolerance mechanism in lentil, thereby assisting in future crop improvement programmes.

Genome-wide identification and expression analysis of the ALDH gene family and functional analysis of PaALDH17 in Prunus avium

ALDH (Aldehyde dehydrogenase), as an enzyme that encodes the dehydroxidization of aldehydes into corresponding carboxylic acids, played an important role inregulating gene expression in response to many kinds of biotic and abiotic stress, including saline-alkali stress. Saline-alkali stress was a common stress that seriously affected plant growth and productivity. Saline-alkali soil contained the characteristics of high salinity and high pH value, which could cause comprehensive damage such as osmotic stress, ion toxicity, high pH, and HCO3-/CO32- stress. In our study, 18 PaALDH genes were identified in sweet cherry genome, and their gene structures, phylogenetic analysis, chromosome localization, and promoter cis-acting elements were analyzed. Quantitative real-time PCR confirmed that PaALDH17 exhibited the highest expression compared to other members under saline-alkali stress. Subsequently, it was isolated from Prunus avium, and transgenic A. thaliana was successfully obtained. Compared with wild type, transgenic PaALDH17 plants grew better under saline-alkali stress and showed higher chlorophyll content, Superoxide dismutase (SOD), Peroxidase (POD) and Catalase (CAT) enzyme activities, which indicated that they had strong resistance to stress. These results indicated that PaALDH17 improved the resistance of sweet cherries to saline-alkali stress, which in turn improved quality and yields.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-024-01444-7.

Overexpression of ZmSTOP1-A Enhances Aluminum Tolerance in Arabidopsis by Stimulating Organic Acid Secretion and Reactive Oxygen Species Scavenging

Aluminum (Al) toxicity and low pH are major factors limiting plant growth in acidic soils. Sensitive to Proton Rhizotoxicity 1 (STOP1) transcription factors respond to these stresses by regulating the expression of multiple Al- or low pH-responsive genes. ZmSTOP1-A, a STOP1-like protein from maize (Zea mays), was localized to the nucleus and showed transactivation activity. ZmSTOP1-A was expressed moderately in both roots and shoots of maize seedlings, but was not induced by Al stress or low pH. Overexpression of ZmSTOP1-A in Arabidopsis Atstop1 mutant partially restored Al tolerance and improved low pH tolerance with respect to root growth. Regarding Al tolerance, ZmSTOP1-A/Atstop1 plants showed clear upregulation of organic acid transporter genes, leading to increased organic acid secretion and reduced Al accumulation in roots. In addition, the antioxidant enzyme activity in roots and shoots of ZmSTOP1-A/Atstop1 plants was significantly enhanced, ultimately alleviating Al toxicity via scavenging reactive oxygen species. Similarly, ZmSTOP1-A could directly activate ZmMATE1 expression in maize, positively correlated with the number of Al-responsive GGNVS cis-elements in the ZmMATE1 promoter. Our results reveal that ZmSTOP1-A is an important transcription factor conferring Al tolerance by enhancing organic acid secretion and reactive oxygen species scavenging in Arabidopsis.

An Oxalate Transporter Gene, AtOT, Enhances Aluminum Tolerance in Arabidopsis thaliana by Regulating Oxalate Efflux

Secretion and efflux of oxalic acid from roots is an important aluminum detoxification mechanism for various plants; however, how this process is completed remains unclear. In this study, the candidate oxalate transporter gene AtOT, encoding 287 amino acids, was cloned and identified from Arabidopsis thaliana. AtOT was upregulated in response to aluminum stress at the transcriptional level, which was closely related to aluminum treatment concentration and time. The root growth of Arabidopsis was inhibited after knocking out AtOT, and this effect was amplified by aluminum stress. Yeast cells expressing AtOT enhanced oxalic acid resistance and aluminum tolerance, which was closely correlated with the secretion of oxalic acid by membrane vesicle transport. Collectively, these results underline an external exclusion mechanism of oxalate involving AtOT to enhance oxalic acid resistance and aluminum tolerance.

Alkaloid production and response to natural adverse conditions in Peganum harmala: in silico transcriptome analyses

Peganum harmala is a valuable wild plant that grows and survives under adverse conditions and produces pharmaceutical alkaloid metabolites. Using different assemblers to develop a transcriptome improves the quality of assembled transcriptome. In this study, a concrete and accurate method for detecting stress-responsive transcripts by comparing stress-related gene ontology (GO) terms and public domains was designed. An integrated transcriptome for P. harmala including 42 656 coding sequences was created by merging de novo assembled transcriptomes. Around 35 000 transcripts were annotated with more than 90% resemblance to three closely related species of Citrus, which confirmed the robustness of the assembled transcriptome; 4853 stress-responsive transcripts were identified. CYP82 involved in alkaloid biosynthesis showed a higher number of transcripts in P. harmala than in other plants, indicating its diverse alkaloid biosynthesis attributes. Transcription factors (TFs) and regulatory elements with 3887 transcripts comprised 9% of the transcriptome. Among the TFs of the integrated transcriptome, cystein2/histidine2 (C2H2) and WD40 repeat families were the most abundant. The Kyoto Encyclopedia of Genes and Genomes (KEGG) MAPK (mitogen-activated protein kinase) signaling map and the plant hormone signal transduction map showed the highest assigned genes to these pathways, suggesting their potential stress resistance. The P. harmala whole-transcriptome survey provides important resources and paves the way for functional and comparative genomic studies on this plant to discover stress-tolerance-related markers and response mechanisms in stress physiology, phytochemistry, ecology, biodiversity, and evolution. P. harmala can be a potential model for studying adverse environmental cues and metabolite biosynthesis and a major source for the production of various alkaloids.

Exogenous 5-aminolevulinic acid alleviates low-temperature injury by regulating glutathione metabolism and β-alanine metabolism in tomato seedling roots

Food availability represents a major worldwide concern due to climate change and population growth. Low-temperature stress (LTS) severely restricts the growth of tomato seedlings. Exogenous 5-aminolevulinic acid (ALA) can alleviate the harm of abiotic stress including LTS; however, data on its protective mechanism on tomato seedling roots, the effects of organelle structure, and the regulation of metabolic pathways under LTS are lacking. In this study, we hope to fill the above gaps by exploring the effects of exogenous ALA on morphology, mitochondrial ultrastructure, reactive oxygen species (ROS) enrichment, physiological indicators, related gene expression, and metabolic pathway in tomato seedlings root under LTS. Results showed that ALA pretreatment could increase the activity of antioxidant enzymes and the content of antioxidant substances in tomato seedlings roots under LTS to scavenge the massively accumulated ROS, thereby protecting the mitochondrial structure of roots and promoting root development under LTS. Combined transcriptomic and metabolomic analysis showed that exogenous ALA pretreatment activated the glutathione metabolism and β-alanine metabolism of tomato seedling roots under LTS, further enhanced the scavenging ability of tomato seedling roots to ROS, and improved the low-temperature tolerance of tomato seedlings. The findings provide a new insight into the regulation of the low-temperature tolerance of tomato by exogenous ALA.