BnA1.CER4 and BnC1.CER4 are redundantly involved in branched primary alcohols in the cuticle wax of Brassica napus

Down-regulated BNC1 promotes glioma by inhibiting ferroptosis via TCF21/PI3K signaling pathway BNC1TCF21PI3K

We elucidate the role of the BNC1 gene in glioma and its potential mechanism. The expression levels of BNC1 in patients with glioma or corresponding cell lines were down-regulated. High BNC1 expression increased survival rate in patients with glioma. BNC1 gene reduced cell proliferation, and enhanced ferroptosis of glioma cells through the induction of TCF21/PI3K signaling pathway. Meanwhile, BNC1 gene could decline tumor proliferation in mice model of glioma. The ferroptosis inhibitor alleviated the impact of BNC1 on glioma ferroptosis, while the ferroptosis agonist weakened the effect of BNC1 on glioma ferroptosis. SiTCF21 also declined the effects of BNC1 on ferroptosis of glioma. The enhanced expression of TCF21 also inhibited the effect of BNC1 on ferroptosis of glioma. BNC1 protein interlinked with TCF21 protein, and bioluminescence imaging demonstrated that BNC1 enhanced TCF21 expression in the brain tissue of the mouse model of glioma. In conclusion, BNC1 reduced cell proliferation, and increased ferroptosis of glioma cells by TCF21/PI3K signaling pathway, may be a feasible strategy to treat glioma.

BnUC1 Is a Key Regulator of Epidermal Wax Biosynthesis and Lipid Transport in Brassica napus

The bHLH (basic helix-loop-helix) transcription factor AtCFLAP2 regulates epidermal wax accumulation, but the underlying molecular mechanism remains unknown. We obtained BnUC1mut (BnaA05g18250D homologous to AtCFLAP2) from a Brassica napus mutant with up-curling leaves (Bnuc1) and epidermal wax deficiency via map-based cloning. BnUC1mut contains a point mutation (N200S) in the conserved dimerization domain. Overexpressing BnUC1mut in ZS11 (Zhongshuang11) significantly decreased the leaf epidermal wax content, resulting in up-curled and glossy leaves. In contrast, knocking out BnUC1mut in ZS11-NIL (Zhongshuang11-near-isogenic line) restored the normal leaf phenotype (i.e., flat) and significantly increased the leaf epidermal wax content. The point mutation weakens the ability of BnUC1mut to bind to the promoters of VLCFA (very-long-chain fatty acids) synthesis-related genes, including KCS (β-ketoacyl coenzyme synthase) and LACS (long-chain acyl CoA synthetase), as well as lipid transport-related genes, including LTP (non-specific lipid transfer protein). The resulting sharp decrease in the transcription of genes affecting VLCFA biosynthesis and lipid transport disrupts the normal accumulation of leaf epidermal wax. Thus, BnUC1 influences epidermal wax formation by regulating the expression of LTP and genes associated with VLCFA biosynthesis. Our findings provide a foundation for future investigations on the mechanism mediating plant epidermal wax accumulation.

BrBCAT1 mutation resulted in deficiency of epicuticular wax crystal in Chinese cabbage

KEY MESSAGE

BrBCAT1 encoding a branched-chain amino acid aminotransferase was responsible for the glossy trait, which was verified by allelic mutants in Chinese cabbage. The glossy characteristic, thanks to the epicuticular wax crystal deficiency, is an excellent commodity character for leafy vegetables. Herein, two allelic glossy green mutants, wdm11 and wdm12, were isolated from an ethyl methane sulfonate (EMS)-mutagenized population of Chinese cabbage, and the mutant phenotype was recessive inherited. Cryo-SEM detected that epicuticular wax crystal in the mutant leaves was virtually absent. MutMap and Kompetitive allele-specific PCR analyses demonstrated that BraA06g006950.3C (BrBCAT1), homologous to AtBCAT1, encoding a branched-chain amino acid aminotransferase was the candidate gene. A SNP (G to A) on the fourth exon of BrBCAT1 in wdm11 caused the 233rd amino acid to change from glycine (G) to aspartic acid (D). A SNP (G to A) on the second exon of BrBCAT1 in wdm12 led to the 112th amino acid change from glycine (G) to arginine (R). Both of the allelic mutants had genetic structural variation in the candidate gene, which indicated that the mutant phenotype was triggered by the BrBCAT1 mutation. The expression levels of BrBCAT1 and genes related to fatty acid chain extension were decreased significantly in the mutant compared to the wild-type, which might result in epicuticular wax crystal deficiency in the mutants. Our findings proved that the mutation of BrBCAT1 induced the glossy phenotype and provided a valuable gene resource for commodity character improvement in Chinese cabbage.

Characterization of the Fatty Acyl-CoA Reductase (FAR) Gene Family and Its Response to Abiotic Stress in Rice (Oryza sativa L.)

Fatty acyl-CoA reductase (FAR) is an important NADPH-dependent enzyme that can produce primary alcohol from fatty acyl-CoA or fatty acyl-carrier proteins as substrates. It plays a pivotal role in plant growth, development, and stress resistance. Herein, we performed genome-wide identification and expression analysis of FAR members in rice using bioinformatics methods. A total of eight OsFAR genes were identified, and the OsFARs were comprehensively analyzed in terms of phylogenetic relationships, duplication events, protein motifs, etc. The cis-elements of the OsFARs were predicted to respond to growth and development, light, hormones, and abiotic stresses. Gene ontology annotation analysis revealed that OsFAR proteins participate in biological processes as fatty acyl-CoA reductase during lipid metabolism. Numerous microRNA target sites were present in OsFARs mRNAs. The expression analysis showed that OsFARs were expressed at different levels during different developmental periods and in various tissues. Furthermore, the expression levels of OsFARs were altered under abiotic stresses, suggesting that FARs may be involved in abiotic stress tolerance in rice. The findings presented here serve as a solid basis for further exploring the functions of OsFARs.

OsFAR1 is involved in primary fatty alcohol biosynthesis and promotes drought tolerance in rice

MAIN CONCLUSION

OsFAR1 encodes a fatty acyl-CoA reductase involved in biosynthesis of primary alcohols and plays an important role in drought stress response in rice. Cuticular waxes cover the outermost surface of terrestrial plants and contribute to inhibiting nonstomatal water loss and improving plant drought resistance. Primary alcohols are the most abundant components in the leaf cuticular waxes of rice (Oryza sativa), but the biosynthesis and regulation of primary alcohol remain largely unknown in rice. Here, we identified and characterized an OsFAR1 gene belonging to the fatty acyl-CoA reductases (FARs) via a homology-based approach in rice. OsFAR1 was activated by abiotic stresses and abscisic acid, resulting in increased production of primary alcohol in rice. Heterologous expression of OsFAR1 enhanced the amounts of C22:0 and C24:0 primary alcohols in yeast (Saccharomyces cerevisiae) and C24:0 to C32:0 primary alcohols in Arabidopsis. Similarly, OsFAR1 overexpression significantly increased the content of C24:0 to C30:0 primary alcohols on rice leaves. Finally, OsFAR1 overexpression lines exhibited reduced cuticle permeability and enhanced drought tolerance in rice and Arabidopsis. Taken together, our results demonstrate that OsFAR1 is involved in rice primary alcohol biosynthesis and plays an important role in responding to drought and other environmental stresses.

Identification of an epicuticular wax crystal deficiency gene Brwdm1 in Chinese cabbage (Brassica campestris L. ssp. pekinensis)

Introduction

The cuticle wax covering the plant surface is a whitish hydrophobic protective barrier in Chinese cabbage, and the epicuticular wax crystal deficiency normally has higher commodity value for a tender texture and glossy appearance. Herein, two allelic epicuticular wax crystal deficiency mutants, wdm1 and wdm7, were obtained from the EMS mutagenesis population of a Chinese cabbage DH line 'FT'.

Methods

The cuticle wax morphology was observed by Cryo-scanning electron microscopy (Cryo-SEM) and the composition of wax was determined by GC-MS. The candidate mutant gene was found by MutMap and validated by KASP. The function of candidate gene was verified by allelic variation.

Results

The mutants had fewer wax crystals and lower leaf primary alcohol and ester content. Genetic analysis revealed that the epicuticular wax crystal deficiency phenotype was controlled by a recessive nuclear gene, named Brwdm1. MutMap and KASP analyses indicated that BraA01g004350.3C, encoding an alcohol-forming fatty acyl-CoA reductase, was the candidate gene for Brwdm1. A SNP 2,113,772 (C to T) variation in the 6^th exon of Brwdm1 in wdm1 led to the 262^nd amino acid substitution from threonine (T) to isoleucine (I), which existed in a rather conserved site among the amino acid sequences from Brwdm1 and its homologs. Meanwhile, the substitution changed the three-dimensional structure of Brwdm1. The SNP 2,114,994 (G to A) in the 10^th exon of Brwdm1 in wdm7 resulted in the change of the 434^th amino acid from valine (V) to isoleucine (I), which occurred in the STERILE domain. KASP genotyping showed that SNP 2,114,994 was co-segregated with glossy phenotype. Compared with the wild type, the relative expression of Brwdm1 was significantly decreased in the leaves, flowers, buds and siliques of wdm1.

Discussion

These results indicated that Brwdm1 was indispensable for the wax crystals formation and its mutation resulted in glossy appearance in Chinese cabbage.

Genome-wide-association study and transcriptome analysis reveal the genetic basis controlling the formation of leaf wax in Brassica napus

Cuticular wax protects plants from various biotic and abiotic stresses. However, the genetic network of wax biosynthesis and the environmental factors influencing leaf wax production in rapeseed (Brassica napus) remains unclear. Here, we demonstrated the role of leaf wax in the resistance to Sclerotinia infection in rapeseed. We found that leaves grown under high light intensity had higher expression of genes involved in wax biosynthesis, and produced more wax on the leaf surface, compared with those grown under low light conditions. Genome-wide association study (GWAS) identified 89 single nucleotide polymorphisms significantly associated with leaf wax coverage. A cross-analysis between GWAS and differentially expressed genes (DEGs) in the leaf epidermis of the accessions with contrasting differences in wax content revealed 17 candidate genes that control this variation in rapeseed. Selective sweep analysis combined with DEG analysis unveiled 510 candidate genes with significant selective signatures. From the candidate genes, we selected BnaA02.LOX4, a putative lipoxygenase, and BnaCnn.CER1, BnaA02.CER3, BnaC02.CER3, and BnaA01.CER4 (ECERIFERUM1-4) that were putatively responsible for wax biosynthesis, to analyse the allelic forms and haplotypes corresponding to high or low leaf wax coverage. These data enrich our knowledge about wax formation, and provide a gene pool for breeding an ideal leaf wax content in rapeseed.

Silencing of Pepper CaFtsH1 or CaFtsH8 Genes Alters Normal Leaf Development

Filamentation temperature-sensitive H (FtsH) is a proteolytic enzyme that plays an important role in plant photomorphogenesis and stress resistance. However, information regarding the FtsH family genes in pepper is limited. In our research, through genome-wide identification, 18 members of the pepper FtsH family (including five FtsHi members) were identified and renamed based on phylogenetic analysis. CaFtsH1 and CaFtsH8 were found to be essential for pepper chloroplast development and photosynthesis because FtsH5 and FtsH2 were lost in Solanaceae diploids. We found that the CaFtsH1 and CaFtsH8 proteins were located in the chloroplasts and specifically expressed in pepper green tissues. Meanwhile, CaFtsH1 and CaFtsH8-silenced plants created by virus-induced gene silencing exhibited albino leaf phenotypes. In addition, CaFtsH1-silenced plants were observed to contain very few dysplastic chloroplasts and lost the capacity for photoautotrophic growth. Transcriptome analysis revealed that the expression of chloroplast-related genes such as those coding the photosynthesis-antenna protein and structural proteins was downregulated in CaFtsH1-silenced plants, resulting in the inability to form normal chloroplasts. This study improves our understanding of pepper chloroplast formation and photosynthesis through the identification and functional study of CaFtsH genes.

The Plant Fatty Acyl Reductases

Fatty acyl reductase (FAR) is a crucial enzyme that catalyzes the NADPH-dependent reduction of fatty acyl-CoA or acyl-ACP substrates to primary fatty alcohols, which in turn acts as intermediate metabolites or metabolic end products to participate in the formation of plant extracellular lipid protective barriers (e.g., cuticular wax, sporopollenin, suberin, and taproot wax). FARs are widely present across plant evolution processes and play conserved roles during lipid synthesis. In this review, we provide a comprehensive view of FAR family enzymes, including phylogenetic analysis, conserved structural domains, substrate specificity, subcellular localization, tissue-specific expression patterns, their varied functions in lipid biosynthesis, and the regulation mechanism of FAR activity. Finally, we pose several questions to be addressed, such as the roles of FARs in tryphine, the interactions between transcription factors (TFs) and FARs in various environments, and the identification of post-transcriptional, translational, and post-translational regulators.

The production of wax esters in transgenic plants: towards a sustainable source of bio-lubricants

Wax esters are high-value compounds used as feedstocks for the production of lubricants, pharmaceuticals, and cosmetics. Currently, they are produced mostly from fossil reserves using chemical synthesis, but this cannot meet increasing demand and has a negative environmental impact. Natural wax esters are also obtained from Simmondsia chinensis (jojoba) but comparably in very low amounts and expensively. Therefore, metabolic engineering of plants, especially of the seed storage lipid metabolism of oil crops, represents an attractive strategy for renewable, sustainable, and environmentally friendly production of wax esters tailored to industrial applications. Utilization of wax ester-synthesizing enzymes with defined specificities and modulation of the acyl-CoA pools by various genetic engineering approaches can lead to obtaining wax esters with desired compositions and properties. However, obtaining high amounts of wax esters is still challenging due to their negative impact on seed germination and yield. In this review, we describe recent progress in establishing non-food-plant platforms for wax ester production and discuss their advantages and limitations as well as future prospects.

Arabidopsis ACYL-ACTIVATING ENZYME 9 (AAE9) encoding an isobutyl-CoA synthetase is a key factor connecting branched-chain amino acid catabolism with iso-branched wax biosynthesis

Iso-branched wax compounds are well known in plants, but their biosynthetic pathways are still mostly unknown. It has been speculated that branched waxes are derived from branched-chain amino acid (BCAA) catabolism, but the evidence for this is very limited. Gas chromatography-flame ionisation detection (GC-FID) analysis revealed that mutations in two subunits of the branched-chain ketoacid dehydrogenase (BCKDH) complex, a key enzyme complex in the degradation of BCAAs, significantly decreased the amounts of branched wax compounds, indicating that BCAA degradation may be integral to the synthesis of iso-branched wax. Substrate feeding studies further revealed that the metabolic precursor of iso-branched wax compounds is isobutyric acid (iBA), which is derived from valine degradation in Arabidopsis. We also isolated a novel mutant and found that its branched wax deficient phenotype could not be rescued by iBA. Map-based cloning together with complementation analysis revealed that mutation in ACYL-ACTIVATING ENZYME 9 (AAE9) is responsible for this phenotype. Genetic and enzyme activity analysis demonstrated that AAE9 is located downstream of the BCAA degradation pathway, and that it activates iBA to isobutyryl-CoA for use on branched wax synthesis. Taken together, our study demonstrates that AAE9 is a key factor connecting BCAA catabolism with branched wax biosynthesis.

A putative SUBTILISIN-LIKE SERINE PROTEASE 1 (SUBSrP1) regulates anther cuticle biosynthesis and panicle development in rice

INTRODUCTION

Panicle abortion is a severe physiological defect and causes a reduction in grain yield.

OBJECTIVES

In this study, we aim to provide the characterization and functional analysis of a mutant apa1331 (apical panicle abortion1331).

METHODS

The isolated mutant from an EMS-mutagenized population was subjected to SSR analysis and Mutmap assay for candidate gene mapping. We performed phenotypic analysis, anthers cross-sections morphology, wax and cutin profiling, biochemical assays and phylogenetic analysis for characterization and evaluation of apa1331. We used CRISPR/Cas9 disruption for functional validation of its candidate gene. Furthermore, comparative RNA-seq and relative expression analysis were performed to get further insights into mechanistic role of the candidate gene.

RESULTS

The anthers from the apical spikelets of apa1331 were degenerated, pollen-less and showed defects in cuticle formation. Transverse sections of apa1331 anthers showed defects in post-meiotic microspore development at stage 8-9. Gas Chromatography showed a significant reduction of wax and cutin in anthers of apa1331 compared to Wildtype (WT). Quantification of H₂O₂ and MDA has indicated the excessive ROS (reactive oxygen species) in apa1331. Trypan blue staining and TUNEL assay revealed cell death and excessive DNA fragmentation in apa1331. Map-based cloning and Mutmap analysis revealed that LOC_Os04g40720, encoding a putative SUBTILISIN-LIKE SERINE PROTEASE (OsSUBSrP1), harbored an SNP (A > G) in apa1331. Phenotypic defects were only seen in apical spikelets due to highest expression of OsSUBSrP1 in upper panicle portion. CRISPR-mediated knock-out lines of OsSUBSrP1 displayed spikelet abortion comparable to apa1331. Global gene expression analysis revealed a significant downregulation of wax and cutin biosynthesis genes.

CONCLUSIONS

Our study reports the novel role of SUBSrP1 in anther cuticle biosynthesis by ROS-mediated programmed cell death in rice.

Comprehensive genomics and expression analysis of eceriferum (CER) genes in sunflower (Helianthus annuus)

Sunflower occupies the fourth position among oilseed crops the around the world. Eceriferum (CER) is an important gene family that plays critical role in very-long-chain fatty acids elongation and biosynthesis of epicuticular waxes under both biotic and abiotic stress conditions. The aim of present study was to investigate the effect of sunflower CER genes during drought stress condition. Thus, comparative analysis was undertaken for sunflower CER genes with Arabidopsis genome to determine phylogenetic relationship, chromosomal mapping, gene structures, gene ontology and conserved motifs. Furthermore, we subjected the sunflower cultivars under drought stress and used qRT-PCR analysis to explore the expression pattern of CER genes during drought conditions. We identified thirty-seven unevenly distributed CER genes in the sunflower genome. The phylogenetic analysis revealed that CER genes were grouped into seven clades in Arabidopsis, Helianthus annuus, and Gossypium hirsutum. Expression analysis showed that genes CER10 and CER60 were upregulated in sunflower during drought conditions, indicating that these genes are activated during drought stress. The results obtained will serve to characterize the CER gene family in sunflower and exploit the role of these genes in wax biosynthesis under limited water conditions.

Key message

Cuticular waxes protect the plants from drought stress, so we observed the expression of wax bio synthesis genes in recently sequences genome of Helianthus annuus. We observed that expression of wax biosynthesis genes CER10 and CER60 was upregulated when the plants were subjected to drought stress.