Plant Acyl-CoA-Binding Proteins-Their Lipid and Protein Interactors in Abiotic and Biotic Stresses

NMR-Based Metabolomic Analysis of Biotic Stress Responses in the Traditional Korean Landrace Red Pepper (Capsicum annuum var. annuum, cv. Subicho)

Korean landrace red peppers (Capsicum annuum var. Subicho), such as the traditional representative Subicho variety, are integral to Korean foods and are often consumed raw or used as a dried powder for cuisine. However, the known vulnerability of local varieties of landrace to biotic stresses can compromise their quality and yield. We employed nuclear magnetic resonance (NMR) spectroscopy coupled with a multivariate analysis to uncover and compare the metabolomic profiles of healthy and biotic-stressed Subicho peppers. We identified 42 metabolites, with significant differences between the groups. The biotic-stressed Subicho red peppers exhibited lower sucrose levels but heightened concentrations of amino acids, particularly branched-chain amino acids (valine, leucine, and isoleucine), suggesting a robust stress resistance mechanism. The biotic-stressed red peppers had increased levels of TCA cycle intermediates (acetic, citric, and succinic acids), nitrogen metabolism-related compounds (alanine, asparagine, and aspartic acid), aromatic amino acids (tyrosine, phenylalanine, and tryptophan), and γ-aminobutyric acid. These findings reveal the unique metabolic adaptations of the Subicho variety, underscoring its potential resilience to biotic stresses. This novel insight into the stress response of the traditional Subicho pepper can inform strategies for developing targeted breeding programs and enhancing the quality and economic returns in the pepper and food industries.

Acyl-CoA-binding protein (ACBP) genes involvement in response to abiotic stress and exogenous hormone application in barley (Hordeum vulgare L.)

BACKGROUND

Acyl-CoA-Binding proteins (ACBPs) function as coenzyme A transporters and play important roles in regulating plant growth and development in response to abiotic stress and phytohormones, as well as in membrane repair. To date, the ACBP family has not been a comprehensively characterized in barley (Hordeum vulgare L.).

RESULTS

Eight ACBP genes were identified in the barley genome and named as HvACBP1-8. The analysis of the proteins structure and promoter elements of HvACBP suggested its potential functions in plant growth, development, and stress response. These HvACBPs are expressed in specific tissues and organs following induction by abiotic stressors such as drought, salinity, UV-B exposure, temperature extremes, and exposure to exogenous phytohormones. The HvACBP7 and HvACBP8 amino acid sequences were conserved during the domestication of Tibetan Qingke barley.

CONCLUSIONS

Acyl-CoA-binding proteins may play important roles in barley growth and environmental adaptation. This study provides foundation for further analyses of the biological functions of HvACBPs in the barley stress response.

Acyl-CoA binding protein is required for lipid droplet degradation in the diatom Phaeodactylum tricornutum

Diatoms (Bacillariophyceae) accumulate neutral storage lipids in lipid droplets during stress conditions, which can be rapidly degraded and recycled when optimal conditions resume. Since nutrient and light availability fluctuate in marine environments, storage lipid turnover is essential for diatom dominance of marine ecosystems. Diatoms have garnered attention for their potential to provide a sustainable source of omega-3 fatty acids. Several independent proteomic studies of lipid droplets isolated from the model oleaginous pennate diatom Phaeodactylum tricornutum have identified a previously uncharacterized protein with an acyl-CoA binding (ACB) domain, Phatrdraft_48778, here referred to as Phaeodactylum tricornutum acyl-CoA binding protein (PtACBP). We report the phenotypic effects of CRISPR-Cas9 targeted genome editing of PtACBP. ptacbp mutants were defective in lipid droplet and triacylglycerol degradation, as well as lipid and eicosapentaenoic acid synthesis, during recovery from nitrogen starvation. Transcription of genes responsible for peroxisomal β-oxidation, triacylglycerol lipolysis, and eicosapentaenoic acid synthesis was inhibited. A lipid-binding assay using a synthetic ACB domain from PtACBP indicated preferential binding specificity toward certain polar lipids. PtACBP fused to eGFP displayed an endomembrane-like pattern, which surrounded the periphery of lipid droplets. PtACBP is likely responsible for intracellular acyl transport, affecting cell division, development, photosynthesis, and stress response. A deeper understanding of the molecular mechanisms governing storage lipid turnover will be crucial for developing diatoms and other microalgae as biotechnological cell factories.

Identification of novel sources of partial and incomplete hypersensitive resistance to rust and associated genomic regions in common bean

Common bean (Phaseolus vulgaris) is one of the legume crops most consumed worldwide and bean rust is one of the most severe foliar biotrophic fungal diseases impacting its production. In this work, we searched for new sources of rust resistance (Uromyces appendiculatus) in a representative collection of the Portuguese germplasm, known to have accessions with an admixed genetic background between Mesoamerican and Andean gene pools. We identified six accessions with incomplete hypersensitive resistance and 20 partially resistant accessions of Andean, Mesoamerican, and admixed origin. We detected 11 disease severity-associated single-nucleotide polymorphisms (SNPs) using a genome-wide association approach. Six of the associations were related to partial (incomplete non-hypersensitive) resistance and five to incomplete hypersensitive resistance, and the proportion of variance explained by each association varied from 4.7 to 25.2%. Bean rust severity values ranged from 0.2 to 49.1% and all the infection types were identified, reflecting the diversity of resistance mechanisms deployed by the Portuguese germplasm.The associations with U. appendiculatus partial resistance were located in chromosome Pv08, and with incomplete hypersensitive resistance in chromosomes Pv06, Pv07, and Pv08, suggesting an oligogenic inheritance of both types of resistance. A resolution to the gene level was achieved for eight of the associations. The candidate genes proposed included several resistance-associated enzymes, namely β-amylase 7, acyl-CoA thioesterase, protein kinase, and aspartyl protease. Both SNPs and candidate genes here identified constitute promising genomics targets to develop functional molecular tools to support bean rust resistance precision breeding.

Identification of acyl-CoA-binding protein gene in Triticeae species reveals that TaACBP4A-1 and TaACBP4A-2 positively regulate powdery mildew resistance in wheat

Plant acyl-CoA-binding proteins (ACBPs), which contain the conserved ACB domain, participate in multiple biological processes, however, there are few reports on wheat ACBPs. In this study, the ACBP genes from nine different species were identified comprehensively. The expression patterns of TaACBP genes in multiple tissues and under various biotic stresses were determined by qRT-PCR. The function of selected TaACBP genes was studied by virus-induced gene silencing. A total of 67 ACBPs were identified from five monocotyledonous and four dicotyledonous species and divided into four classes. Tandem duplication analysis of the ACBPs suggested that tandem duplication events occurred in Triticum dicoccoides, but there was no tandem duplication event in wheat ACBP genes. Evolutionary analysis suggested that the TdACBPs may have experienced gene introgression during tetraploid evolution, while TaACBP gene loss events occurred during hexaploid wheat evolution. The expression pattern showed that all the TaACBP genes were expressed, and most of them were responsive to induction by Blumeria graminis f. sp. tritici or Fusarium graminearum. Silencing of TaACBP4A-1 and TaACBP4A-2 increased powdery mildew susceptibility in the common wheat BainongAK58. Furthermore, TaACBP4A-1, which belonged to class III, physically interacted with autophagy-related ubiquitin-like protein TaATG8g in yeast cells. This study provided a valuable reference for further investigations into the functional and molecular mechanisms of the ACBP gene family.

Comparative metabolomics of root-tips reveals distinct metabolic pathways conferring drought tolerance in contrasting genotypes of rice

Background

The mechanisms underlying rice root responses to drought during the early developmental stages are yet unknown.

Results

This study aimed to determine metabolic differences in IR64, a shallow-rooting, drought-susceptible genotype, and Azucena, a drought-tolerant and deep-rooting genotype under drought stress. The morphological evaluation revealed that Azucena might evade water stress by increasing the lateral root system growth, the root surface area, and length to access water. At the same time, IR64 may rely mainly on cell wall thickening to tolerate stress. Furthermore, significant differences were observed in 49 metabolites in IR64 and 80 metabolites in Azucena, for which most metabolites were implicated in secondary metabolism, amino acid metabolism, nucleotide acid metabolism and sugar and sugar alcohol metabolism. Among these metabolites, a significant positive correlation was found between allantoin, galactaric acid, gluconic acid, glucose, and drought tolerance. These metabolites may serve as markers of drought tolerance in genotype screening programs. Based on corresponding biological pathways analysis of the differentially abundant metabolites (DAMs), biosynthesis of alkaloid-derivatives of the shikimate pathway, fatty acid biosynthesis, purine metabolism, TCA cycle and amino acid biosynthesis were the most statistically enriched biological pathway in Azucena in drought response. However, in IR64, the differentially abundant metabolites of starch and sucrose metabolism were the most statistically enriched biological pathways.

Conclusion

Metabolic marker candidates for drought tolerance were identified in both genotypes. Thus, these markers that were experimentally determined in distinct metabolic pathways can be used for the development or selection of drought-tolerant rice genotypes.

Genome-wide identification of acyl-CoA binding proteins and possible functional prediction in legumes

Acyl-CoA-binding proteins (ACBPs), members of a vital housekeeping protein family, are present in various animal and plant species. They are divided into four classes: small ACBPs (class I), ankyrin-repeat ACBPs (class II), large ACBPs (class III), and kelch-ACBPs (class IV). Plant ACBPs play a pivotal role in intracellular transport, protection, and pool formation of acyl-CoA esters, promoting plant development and stress response. Even though legume crops are important for vegetable oils, proteins, vegetables and green manure, legume ACBPs are not well investigated. To comprehensively explore the functions of ACBPs in nine legumes (Lotus japonicus, Medicago truncatula, Glycine max, Vigna angularis, Vigna radiata, Phaseolus vulgaris, Arachis hypogaea, Arachis duranensis, and Arachis ipaensis), we conducted genome-wide identification of the ACBP gene family. Our evolutionary analyses included phylogenetics, gene structure, the conserved motif, chromosomal distribution and homology, subcellular localization, cis-elements, and interacting proteins. The results revealed that ACBP Orthologs of nine legumes had a high identity in gene structure and conserved motif. However, subcellular localization, cis-acting elements, and interaction protein analyses revealed potentially different functions from previously reported. The predicted results were also partially verified in Arachis hypogaea. We believe that our findings will help researchers understand the roles of ACBPs in legumes and encourage them to conduct additional research.

Features and Possible Applications of Plant Lipid-Binding and Transfer Proteins

In plants, lipid trafficking within and inside the cell is carried out by lipid-binding and transfer proteins. Ligands for these proteins are building and signaling lipid molecules, secondary metabolites with different biological activities due to which they perform diverse functions in plants. Many different classes of such lipid-binding and transfer proteins have been found, but the most common and represented in plants are lipid transfer proteins (LTPs), pathogenesis-related class 10 (PR-10) proteins, acyl-CoA-binding proteins (ACBPs), and puroindolines (PINs). A low degree of amino acid sequence homology but similar spatial structures containing an internal hydrophobic cavity are common features of these classes of proteins. In this review, we summarize the latest known data on the features of these protein classes with particular focus on their ability to bind and transfer lipid ligands. We analyzed the structural features of these proteins, the diversity of their possible ligands, the key amino acids participating in ligand binding, the currently known mechanisms of ligand binding and transferring, as well as prospects for possible application.

The Barley Heavy Metal Associated Isoprenylated Plant Protein HvFP1 Is Involved in a Crosstalk between the Leaf Development and Abscisic Acid-Related Drought Stress Responses

The heavy metal associated isoprenylated plant proteins (HIPPs) are characterized by at least one heavy metal associated (HMA) domain and a C-terminal isoprenylation motif. Hordeum vulgare farnesylated protein 1 (HvFP1), a barley HIPP, is upregulated during drought stress, in response to abscisic acid (ABA) and during leaf senescence. To investigate the role of HvFP1, two independent gain-of-function lines were generated. In a physiological level, the overexpression of HvFP1 results in the delay of normal leaf senescence, but not in the delay of rapid, drought-induced leaf senescence. In addition, the overexpression of HvFP1 suppresses the induction of the ABA-related genes during drought and senescence, e.g., HvNCED, HvS40, HvDhn1. Even though HvFP1 is induced during drought, senescence and the ABA treatment, its overexpression suppresses the ABA regulated genes. This indicates that HvFP1 is acting in a negative feedback loop connected to the ABA signaling. The genome-wide transcriptomic analysis via RNA sequencing revealed that the gain-of-function of HvFP1 positively alters the expression of the genes related to leaf development, photomorphogenesis, photosynthesis and chlorophyll biosynthesis. Interestingly, many of those genes encode proteins with zinc binding domains, implying that HvFP1 may act as zinc supplier via its HMA domain. The results show that HvFP1 is involved in a crosstalk between stress responses and growth control pathways.

Roles of acyl-CoA-binding proteins in plant reproduction

Acyl-CoA-binding proteins (ACBPs) constitute a well-conserved family of proteins in eukaryotes that are important in stress responses and development. Past studies have shown that ACBPs are involved in maintaining, transporting and protecting acyl-CoA esters during lipid biosynthesis in plants, mammals, and yeast. ACBPs show differential expression and various binding affinities for acyl-CoA esters. Hence, ACBPs can play a crucial part in maintaining lipid homeostasis. This review summarizes the functions of ACBPs during the stages of reproduction in plants and other organisms. A comprehensive understanding on the roles of ACBPs during plant reproduction may lead to opportunities in crop improvement in agriculture.