Thiamine functions as a key activator for modulating plant health and broad-spectrum tolerance in cotton

Barley yellow dwarf virus-GAV 17K protein disrupts thiamine biosynthesis to facilitate viral infection in plants

Thiamine functions as a crucial activator modulating plant health and broad-spectrum stress tolerances. However, the role of thiamine in regulating plant virus infection is largely unknown. Here, we report that the multifunctional 17K protein encoded by barley yellow dwarf virus-GAV (BYDV-GAV) interacted with barley pyrimidine synthase (HvTHIC), a key enzyme in thiamine biosynthesis. HvTHIC was found to be localized in chloroplast via an N-terminal 74-amino acid domain. However, the 17K-HvTHIC interaction restricted HvTHIC targeting to chloroplasts and triggered autophagy-mediated HvTHIC degradation. Upon BYDV-GAV infection, the expression of the HvTHIC gene was significantly induced, and this was accompanied by accumulation of thiamine and salicylic acid. Silencing of HvTHIC expression promoted BYDV-GAV accumulation. Transcriptomic analysis of HvTHIC silenced and non-silenced barley plants showed that the differentially expressed genes were mainly involved in plant-pathogen interaction, plant hormone signal induction, phenylpropanoid biosynthesis, starch and sucrose metabolism, photosynthesis-antenna protein, and MAPK signaling pathway. Thiamine treatment enhanced barley resistance to BYDV-GAV. Taken together, our findings reveal a molecular mechanism underlying how BYDV impedes thiamine biosynthesis to uphold viral infection in plants.

The genome of Citrus australasica reveals disease resistance and other species specific genes

BACKGROUND

The finger lime (Citrus australasica), one of six Australian endemic citrus species shows a high natural phenotypic diversity and novel characteristics. The wide variation and unique horticultural features have made this lime an attractive candidate for domestication. Currently no haplotype resolved genome is available for this species. Here we present a high quality, haplotype-resolved reference genome for this species using PacBio HiFi and Hi-C sequencing.

RESULTS

Hifiasm assembly and SALSA scaffolding resulted in a collapsed genome size of 344.2 Mb and 321.1 Mb and 323.2 Mb size for the two haplotypes. The nine pseudochromosomes of the collapsed genome had an N50 of 35.2 Mb, 99.1% genome assembly completeness and 98.9% gene annotation completeness (BUSCO). A total of 41,304 genes were predicted in the nuclear genome. Comparison with C. australis revealed that 13,661 genes in pseudochromosomes were unique in C. australasica. These were mainly involved in plant-pathogen interactions, stress response, cellular metabolic and developmental processes, and signal transduction. The two genomes showed a syntenic arrangement at the chromosome level with large structural rearrangements in some chromosomes. Genetic variation among five C. australasica cultivars was analysed. Genes related to defense, synthesis of volatile compounds and red/yellow coloration were identified in the genome. A major expansion of genes encoding thylakoid curvature proteins was found in the C. australasica genome.

CONCLUSIONS

The genome of C. australasica present in this study is of high quality and contiguity. This genome helps deepen our understanding of citrus evolution and reveals disease resistance and quality related genes with potential to accelerate the genetic improvement of citrus.

Alleviation of drought stress through foliar application of thiamine in two varieties of pea (Pisum sativum L.)

Drought stress poorly impacts many morphological and physio-biochemical processes in plants. Pea (Pisum sativum L.) plants are highly nutritious crops destined for human consumption; however, their productivity is threatened under drought stress. Thiamine (vitamin B1) is well-known essential micronutrient, acting as a cofactor in key metabolic processes. Therefore, this study was designed to examine the protective effect of foliar application of thiamine (0, 250, and 500 ppm) on two varieties of pea plants under drought stress. Here, we conducted the pot experiment at the Government College Women University, Faisalabad, to investigate the physio-biochemical and morphological traits of two pea varieties (sarsabz and metior) grown under drought stress and thiamine treatment. Drought stress was applied to plants after germination period of 1 month. Results showed that root fresh and dry weight, shoot fresh and dry weight, number of pods, leaf area, total soluble sugars, total phenolics, total protein contents, catalase, peroxidase, and mineral ions were reduced against drought stress. However, the application of thiamine (both 250 and 500 ppm) overcome the stress and also enhances these parameters, and significantly increases the antioxidant activities (catalase and peroxidase). Moreover, the performance of sarsabz was better under control and drought stress conditions than metior variety. In conclusion, the exogenous application of thiamine enabled the plants to withstand drought stress conditions by regulating several physiological and biochemical mechanisms. In agriculture, it is a great latent to alleviate the antagonistic impact of drought stress on crops through the foliar application of thiamine.

Molecular mechanism of thiamine in mitigating drought stress in Chinese wingnut (Pterocarya stenoptera): Insights from transcriptomics

Urban garden plants are frequently affected by drought, which can hinder their growth, development, and greening effect. Previous studies have indicated that Chinese wingnut (Pterocarya stenoptera) responds to drought stress by increasing the expression of thiamine synthesis genes. In this study, it was found that exogenous thiamine can effectively alleviate the negative effects of drought stress on plants. Forward transcriptome sequencing and physiological tests were further conducted to reveal the molecular mechanism of thiamine in alleviating drought stress. Results showed that exogenous thiamine activated the expression of eight chlorophyll synthesis genes in Chinese wingnut under drought stress. Moreover, physiological indicators proved that chlorophyll content increased in leaves of Chinese wingnut with thiamine treatment under drought stress. Photosynthesis genes were also activated in Chinese wingnut treated with exogenous thiamine under drought stress, as supported by photosynthetic indicators PIabs and PItotal. Additionally, exogenous thiamine stimulated the expression of genes in the auxin-activated signaling pathway, thus attenuating the effects of drought stress. This study demonstrates the molecular mechanism of thiamine in mitigating the effects of drought stress on non-model woody plants lacking transgenic systems. This study also provides an effective method to mitigate the negative impacts of drought stress on plants.

Harnessing enzyme cofactors and plant metabolism: an essential partnership

Cofactors are fundamental to the catalytic activity of enzymes. Additionally, because plants are a critical source of several cofactors (i.e., including their vitamin precursors) within the context of human nutrition, there have been several studies aiming to understand the metabolism of coenzymes and vitamins in plants in detail. For example, compelling evidence has been brought forth regarding the role of cofactors in plants; specifically, it is becoming increasingly clear that an adequate supply of cofactors in plants directly affects their development, metabolism, and stress responses. Here, we review the state-of-the-art knowledge on the significance of coenzymes and their precursors with regard to general plant physiology and discuss the emerging functions attributed to them. Furthermore, we discuss how our understanding of the complex relationship between cofactors and plant metabolism can be used for crop improvement.

Cotton peroxisome-localized lysophospholipase counteracts the toxic effects of Verticillium dahliae NLP1 and confers wilt resistance

Plasma membrane represents a critical battleground between plants and attacking microbes. Necrosis-and-ethylene-inducing peptide 1 (Nep1)-like proteins (NLPs), cytolytic toxins produced by some bacterial, fungal and oomycete species, are able to target on lipid membranes by binding eudicot plant-specific sphingolipids (glycosylinositol phosphorylceramide) and form transient small pores, causing membrane leakage and subsequent cell death. NLP-producing phytopathogens are a big threat to agriculture worldwide. However, whether there are R proteins/enzymes that counteract the toxicity of NLPs in plants remains largely unknown. Here we show that cotton produces a peroxisome-localized enzyme lysophospholipase, GhLPL2. Upon Verticillium dahliae attack, GhLPL2 accumulates on the membrane and binds to V. dahliae secreted NLP, VdNLP1, to block its contribution to virulence. A higher level of lysophospholipase in cells is required to neutralize VdNLP1 toxicity and induce immunity-related genes expression, meanwhile maintaining normal growth of cotton plants, revealing the role of GhLPL2 protein in balancing resistance to V. dahliae and growth. Intriguingly, GhLPL2 silencing cotton plants also display high resistance to V. dahliae, but show severe dwarfing phenotype and developmental defects, suggesting GhLPL2 is an essential gene in cotton. GhLPL2 silencing results in lysophosphatidylinositol over-accumulation and decreased glycometabolism, leading to a lack of carbon sources required for plants and pathogens to survive. Furthermore, lysophospholipases from several other crops also interact with VdNLP1, implying that blocking NLP virulence by lysophospholipase may be a common strategy in plants. Our work demonstrates that overexpressing lysophospholipase encoding genes have great potential for breeding crops with high resistance against NLP-producing microbial pathogens.

Protective effects of thiamine on Wickerhamomyces anomalus against ethanol stress

Wickerhamomyces anomalus (W. anomalus) is widely reported in the brewing industry and has positive effects on the aromatic profiles of wines because of its unique physiological characteristics and metabolic features. However, the accumulation of ethanol during fermentation inhibits the growth of W. anomalus. Thiamine is involved in the response against various abiotic stresses in microorganisms. Therefore, we used transcriptomic and metabolomic analyses to study the effect of thiamine on ethanol-stressed W. anomalus. The results indicate that thiamine could alleviate the inhibitory effect of ethanol stress on the survival of W. anomalus. Differentially expressed genes (DEGs) and differentially expressed metabolites (DEMs) caused by the thiamine intervention were identified as oxidative phosphorylation through integrated transcriptomic and metabolomic analyses. In addition, ethanol treatment decreased the content of intracellular adenosine triphosphate (ATP), while thiamine partially alleviated this phenomenon. The present comprehensive transcriptional overview and metabolomic analysis provide insights about the mechanisms of thiamine protection on W. anomalus under ethanol stress and promote the potential applications of W. anomalus in the fermentation industry.