Biology subjects

Tzin, V.

Publications and source records attributed to Tzin, V..

8 recordsLinked to original sources

bioRxiv2024

Title: Diurnal rhythms in durum wheat triggered by Rhopalosiphum padi (bird cherry-oat 2 aphid)

Wheat is a staple crop and one of the most widely consumed grains globally. Wheat yields can experience significant losses due to the damaging effects of herbivore infestation. However, little is known about the effect aphids have on the natural diurnal rhythms in plants. Our time-series transcriptomics and metabolomics study reveal intriguing molecular changes occurring in plant diurnal rhythmicity upon aphid infestation. Under control conditions, 15,366 out of the 66,559 genes in the tetraploid wheat cultivar Svevo, representing approximately 25% of the transcriptome, exhibited diurnal rhythmicity. Upon aphid infestation, 5,682 genes lost their rhythmicity, while additional 5,203 genes began to exhibit diurnal rhythmicity. The aphid-induced rhythmic genes were enriched in GO terms associated with plant defense, such as protein phosphorylation and cellular response to ABA and were enriched with motifs of the WRKY transcription factor families. Conversely, the genes that lost rhythmicity due to aphid infestation were enriched with motifs of the TCP and ERF transcription factor families. While the core circadian clock genes maintain their rhythmicity during infestation, we observed that approximately 60% of rhythmic genes experience disruptions in their rhythms during aphid infestation. These changes can influence both the plants growth and development processes as well as defense responses. Furthermore, analysis of rhythmic metabolite composition revealed that several monoterpenoids gained rhythmic activity under infestation, while saccharides retained their rhythmic patterns. Our findings highlight the ability of insect infestation to disrupt the natural diurnal cycles in plants, expanding our knowledge of the complex interactions between plants and insects.

plant biology↗

bioRxiv2024

Diurnal rhythmicity in salivary effector expression and metabolism shapes aphid performance on wheat plants

Diurnal rhythms influence insect behavior, physiology, and metabolism, optimizing their performance by adapting to daily changes in the environment. While their impact on agricultural pests has been briefly explored, our understanding of how these rhythms drive adaptative responses in pest biology and influence host colonization remains elusive. Here, we show that a notorious global aphid pest, Rhopalosiphum padi, exhibits distinct diurnal patterns in feeding behavior, with elevated honeydew excretion at night and extended phloem salivation during early nighttime. Temporal aphid transcriptome profiling reveals four diurnally rhythmic clusters, two of which peak at night, exhibiting enrichment in carbohydrate and amino acid metabolism. Beyond the established role in manipulating host responses and allowing sustained feeding, our study reveals novel evidence of cyclical fluctuations in salivary effector expression in an insect species. Silencing key effector genes, peaking in expression during the increased nighttime salivation, results in a more pronounced reduction in aphid excretion activity on host plants during the night compared to the day, a phenomenon not observed on artificial diets. A better understanding of aphid diurnal rhythms and their roles in shaping aphid performance provides a promising avenue to refine and optimize pest management, granting a strategic advantage for minimizing crop damage.

systems biology↗

bioRxiv2023

Self-eating while being eaten: Elucidating the relationship between aphid feeding and the plant autophagy machinery in Arabidopsis leaves

Autophagy, an intracellular process that facilitates the degradation of cytoplasmic materials, plays a dominant role in plant fitness and immunity. While autophagy was shown to be involved in plant response to fungi, bacteria, and viruses, its role in response to insect herbivory is as yet unknown. In this study, we demonstrate a role of autophagy in plant defense against herbivory using Arabidopsis thaliana and the green peach aphid, Myzus persicae. Following six hours of aphid infestation of wildtype plants, we observed high expression of the autophagy-related genes ATG8a and ATG8f, as well as NBR1 (Next to BRCA1 gene 1), a selective autophagy receptor. Moreover, the number of autophagosomes detected by the overexpression of GFP-fused ATG8f in Arabidopsis increased upon aphid infestation. Following this, atg5.1 and atg7.2 mutants were used to study the effect of autophagy on aphid reproduction and feeding behavior. While aphid reproduction on both mutants was lower than on wildtype, feeding behavior was only affected by atg7.2 mutants. Moreover, upon aphid feeding, the Phytoalexin-deficient 4 (PAD4) defense gene was upregulated in wildtype plants but not affected in the mutants. By contrast, the hydrogen peroxide content was much higher in the mutants relative to wildtype, which might have disturbed aphid reproduction and interfered with their feeding. Additionally, an analysis of the phloem sap metabolite profile revealed that atg7.2 mutant plants have lower levels of amino acids and sugars. These findings, together with the high hydrogen peroxide levels, suggest that aphids might exploit the plant autophagy mechanism for their survival.

plant biology↗

bioRxiv2022

Horizontally transferred genes as RNA interference targets for aphid and whitefly control

RNA interference (RNAi)-based technologies are starting to be commercialized as a new approach for agricultural pest control. Horizontally transferred genes (HTGs), which have been transferred into insect genomes from viruses, bacteria, fungi, or plants, are attractive targets for RNAi-mediated pest control. HTGs are often unique to a specific insect family or even genus, making it unlikely that RNAi constructs targeting such genes will have negative effects on ladybugs, lacewings, and other beneficial predatory insect species. In this study, we sequenced the genome of a red, tobacco-adapted isolate of Myzus persicae (green peach aphid) and bioinformaticaly identified 30 HTGs. We then used plant-mediated virus-induced gene silencing (VIGS) to show that several HTGs of bacterial and plant origin are important for aphid growth and/or survival. Silencing the expression of fungal HTGs did not affect aphid survivorship, but decreased aphid reproduction. Importantly, although there was uptake of plant-expressed RNA by Coccinella septempunctata (seven-spotted ladybugs) via the aphids that they consumed, we did not observe negative effects on ladybugs from aphid-targeted VIGS constructs. In other experiments, we targeted five Bemisia tabaci (whitefly) HTGs using VIGS and demonstrated that knockdown of some of these genes affected whitefly survival. As functional HTGs have been identified in the genomes of numerous pest species, we propose that these HTGs should be explored further as efficient and safe targets for control of insect pests using plant-mediated RNA interference.

plant biology↗

bioRxiv2021

The wheat dioxygenase BX6 is involved in the formation of benzoxazinoids in planta and contributes to plant defense against insect herbivores

Benzoxazinoids are plant specialized metabolites with defense properties, highly abundant in wheat (Triticum), one of the worlds most important crops. The goal of our study was to characterize dioxygenase BX6 genes in tetraploid and hexaploid wheat genotypes and to elucidate their effects on defense against herbivores. Phylogenetic analysis revealed four BX6 genes in the hexaploid wheat T. aestivum, but only one ortholog was found in tetraploid (T. turgidum) wild emmer wheat and the cultivated durum wheat. Transcriptome sequencing of durum wheat plants damaged either by aphids or caterpillars revealed that several BX genes including TtBX6 were upregulated upon caterpillar feeding relative to undamaged control plants. A virus-induced gene silencing approach was used to reduce the expression of BX6 in T. aestivum plants and exhibited both reduced transcript levels and reduced accumulation of different benzoxazinoids. To elucidate the effect of BX6 on plant defense, bioassays with different herbivores feeding on BX6-silenced leaves were conducted. The results showed that plants with silenced BX6 were more susceptible to aphids and the two-spotted spider mite compared to controls. Overall, our study indicates that wheat BX6 is involved in the formation of benzoxazinoids in planta and contributes to plant resistance against insect herbivores.

plant biology↗

bioRxiv2019

Characterizing the serotonin biosynthesis pathway upon aphid infestation in Setaria viridis leaves

Setaria viridis (green foxtail millet), a short life-cycle C4 plant in the Gramineae, serves as a resilient crop that provides good yield even in dry and marginal land. Although S. viridis has been studied extensively in the last decade, its defense responses, in particular the chemical defensive metabolites that protect it against insect herbivory, are unstudied. To characterize S. viridis defense responses, we conducted transcriptomic and metabolomic assays of plants infested with aphids and caterpillars. Pathway enrichment analysis indicated massive transcriptomic changes that involve genes from amino acid biosynthesis and degradation, secondary metabolites and phytohormone biosynthesis. The Trp-derived metabolite serotonin was notably induced by insect feeding. Through comparisons with known rice serotonin biosynthetic genes, we identified several predicted S. viridis Trp decarboxylases and cytochrome P450 genes that were up-regulated in response to insect feeding. The function of one Trp decarboxylase was validated by ectopic expression and detection of tryptamine accumulation in Nicotiana tabacum. To validate the defensive properties of serotonin, we used an artificial diet assay to show reduced Rhopalosiphum padi aphid survival with increasing serotonin concentrations. This demonstrated that serotonin is a defensive metabolite in S. viridis and is fundamental for understanding the adaptation of it to biotic stresses.\n\nHIGHLIGHTA combined transcriptomic and metabolomic profiling of Setaria viridis leaves response to aphid and caterpillar infestation identifies the genes related to the biosynthesis of serotonin and their function in defense.

plant biology↗

bioRxiv2017

Spodoptera exigua caterpillar feeding induces rapid defense responses in maize leaves

Insects such as beet armyworm caterpillars (Spodoptera exigua) cause extensive damage to maize (Zea mays) by consuming foliar tissue. Maize plants respond to such insect attack by triggering defense mechanisms that involve large changes in gene expression and the biosynthesis of specialized metabolites and defense signaling molecules. To investigate dynamic maize responses to herbivore feeding, leaves of maize inbred line B73 were infested with S. exigua caterpillars for 1 to 24 hours, followed by comprehensive transcriptomic and metabolomic characterization. Our results show that the most significant gene expression responses of maize to S. exigua feeding occur at early time points, within 4 to 6 hours after caterpillar infestation. However, both gene expression and metabolite profiles continued changing during the entire 24-hour experiment while photosynthesis genes were gradually decreased. The primary and specilaze metabolism shift maught be temporal and dynamic processes in the infested leaf tissue. We analyzed the effects of mutating genes in two major defense-related pathways, benzoxazinoids (Bx1 and Bx2) and jasmonic acid (Lox8), using Dissociation (Ds) transposon insertions in maize inbred line W22. Together, these results show that maize leaves shift to implementation of chemical defenses within one hour after the initiation of caterpillar attack. Thus, the induced biosynthesis of specialized metabolites can have major effects in maize-caterpillar interactions.\n\nHIGHLIGHTA comprehensive transcriptic and metabolomic profiling time course of maize foliar responses to caterpillar feeding identifies genes for the synthesis of benzoxazinoids and phytohormones.

plant biology↗

bioRxiv2016

A global co-expression network approach for connecting genes to specialized metabolic pathways in plants

Plants produce a tremendous diversity of specialized metabolites (SMs) to interact with and manage their environment. A major challenge hindering efforts to tap this seemingly boundless source of pharmacopeia is the identification of SM pathways and their constituent genes. Given the well-established observation that the genes comprising a SM pathway are co-regulated in response to specific environmental conditions, we hypothesized that genes from a given SM pathway would form tight associations (modules) with each other in gene co-expression networks, facilitating their identification. To evaluate this hypothesis, we used 10 global co-expression datasets--each a meta-analysis of hundreds to thousands of expression experiments--across eight plant model organisms to identify hundreds of modules of co-expressed genes for each species. In support of our hypothesis, 15.3-52.6% of modules contained two or more known SM biosynthetic genes (e.g., cytochrome P450s, terpene synthases, and chalcone synthases), and module genes were enriched in SM functions (e.g., glucoside and flavonoid biosynthesis). Moreover, modules recovered many experimentally validated SM pathways in these plants, including all six known to form biosynthetic gene clusters (BGCs). In contrast, genes predicted based on physical proximity on a chromosome to form plant BGCs were no more co-expressed than the null distribution for neighboring genes. These results not only suggest that most predicted plant BGCs do not represent genuine SM pathways but also argue that BGCs are unlikely to be a hallmark of plant specialized metabolism. We submit that global gene co-expression is a rich, but largely untapped, data source for discovering the genetic basis and architecture of plant natural products, which can be applied even without knowledge of the genome sequence.

plant biology↗