Biology subjects

Verma, P. K.

Publications and source records attributed to Verma, P. K..

4 recordsLinked to original sources

bioRxiv2022

Transcriptome analysis reveals robust transcriptional reprogramming during early stages of Cicer-Ascochyta interaction

Ascochyta blight (AB) caused by a filamentous fungus Ascochyta rabiei is a major threat to global chickpea production. The mechanisms underlying chickpea response to A. rabiei remain elusive. Here, we investigated the comparative transcriptional dynamics of AB-resistant and susceptible chickpea genotypes upon A. rabiei infection to understand the early host defence response. Our findings revealed that AB-resistant plants underwent rapid and extensive transcriptional reprogramming compared to susceptible host. At early stage (24-hpi), mainly cell wall remodeling and secondary metabolite pathways were highly activated, while DEGs related with signaling components viz. protein kinases, transcription factors, and hormonal pathways show remarkable upsurge at 72-hpi, especially in resistant genotype. Notably, our data suggests imperative role of JA, ET, and ABA signaling in providing immunity against A. rabiei. Furthermore, gene co-expression networks and modules corroborated the importance of cell wall remodeling, signal transduction and phytohormone pathways. The hub genes such as MYB14, PRE6 and MADS-SOC1 discovered in these modules might be the master regulators governing chickpea immunity. Overall, we not only provide novel insights for comprehensive understanding of immune signaling components mediating AB resistance/susceptibility at early Cicer-Ascochyta interactions, but also offer a valuable resource for developing AB-resistant chickpea. HighlightsComparative transcriptomic and co-expression analysis of AB-resistant and susceptible chickpea genotypes reveals high-amplitude transcriptional dynamics in resistant plants, and also identifies TFs, PKs and phytohormone-crosstalk as core regulators for AB-resistance.

plant biology↗

bioRxiv2021

The nuclear effector ArPEC25 from the necrotrophic fungus Ascochyta rabiei targets the chickpea transcription factor CaβLIM1a and negatively modulates lignin biosynthesis for host susceptibility

Fungal pathogens deploy a barrage of secreted effectors to subvert host immunity, often by evading, disrupting, or altering key components of transcription, defense signaling, and metabolic pathways. However, the underlying mechanisms of effectors and their host targets are largely unexplored in necrotrophic fungal pathogens. Here, we describe the effector protein ArPEC25, which is secreted by the necrotroph Ascochyta rabiei, the causal agent of Ascochyta blight disease in chickpea (Cicer arietinum), and is indispensable for virulence. After entering host cells, ArPEC25 localizes to the nucleus and targets the host LIM transcription factor Ca{beta}LIM1a. Ca{beta}LIM1a is a transcriptional regulator of CaPAL1, which encodes phenylalanine ammonia lyase, the regulatory, gatekeeping enzyme of the phenylpropanoid pathway. ArPEC25 inhibits the transactivation of Ca{beta}LIM1a by interfering with its DNA binding ability. This results in negative regulation of the phenylpropanoid pathway and decreased levels of intermediates of lignin biosynthesis, thereby suppressing lignin production. Our findings illustrate the role of fungal effectors in enhancing virulence by targeting a key defense pathway that leads to the biosynthesis of various secondary metabolites and antifungal compounds. This study provides a template for the study of less explored necrotrophic effectors and their host target functions. One-sentence summaryThe Ascochyta rabiei effector ArPEC25 enters the host nucleus and targets the transcription factor Ca{beta}LIM1a to manipulate phenylpropanoid pathway for negative modulation of chickpea lignin biosynthesis.

plant biology↗

bioRxiv2020

Modulation of fungal virulence through CRZ1 regulated F-BAR-dependent actin remodeling and endocytosis in chickpea infecting phytopathogen Ascochyta rabiei

Polarized hyphal growth of filamentous pathogenic fungi is an essential event for host penetration and colonization. The long-range early endosomal trafficking during the hyphal growth is crucial for nutrient uptake, sensing of host-specific cues, and regulation of effector production. Bin1/Amphiphysin/Rvs167 (BAR) domain-containing proteins mediate fundamental cellular processes, including membrane remodeling and endocytosis. Here, we identified an F-BAR domain protein (ArF-BAR) in the necrotrophic fungus Ascochyta rabiei and demonstrate its involvement in endosome-dependent fungal virulence on the host plant, Cicer arietinum. We show that ArF-BAR regulates endocytosis at the hyphal tip, localizes to the early endosomes, and is involved in actin dynamics. Functional studies involving gene knockout and complementation experiments reveal that ArF-BAR is essential for virulence. The loss-of-function of ArF-BAR results in delayed formation of first septa from the hyphal tip, crucial for host penetration and proliferation. ArF-BAR was induced in response to oxidative stress and infection and localized to endocytic vesicles within the fungal hyphae. We also show that ArF-BAR is able to tubulate synthetic liposomes, suggesting the functional role of F-BAR domain in membrane tubule formation in vivo. Further, our studies identified a stress-induced transcription factor, ArCRZ1 (Calcineurin-responsive zinc finger 1) as key regulator for transcriptional reprogramming of ArF-BAR. We propose a model in which ArCRZ1 functions upstream of ArF-BAR to regulate fungal pathogenesis through a mechanism that involves membrane remodeling and actin cytoskeleton regulation. Author summaryBAR-domain superfamily is known to mold amorphous lipid bilayer into defined tubular shapes and critical for endosome formation and trafficking. Although these processes are studied earlier in the context of their structural and biochemical properties, there is limited evidence on the direct role of F-BAR domain proteins in the pathophysiological development of other economically important fungi. Our study assumes functional significance for plant infection as we identified an F-BAR domain-containing protein that is regulated by a distinct transcriptional network. We characterized F-BAR in a necrotrophic fungal pathogen, Ascochyta rabiei that causes the Ascochyta blight (AB) disease in chickpea plants. Additionally, we have also identified a calcium-regulated CRZ1 transcription factor that regulates the transcription of ArF-BAR. Our study will help to understand the complex interplay underlying the endosome formation required for fungal virulence.

plant biology↗

bioRxiv2020

Insights into structure of Penicillium funiculosum LPMO and its synergistic saccharification performance with CBH1 on high substrate loading upon simultaneous overexpression

Lytic polysaccharide monooxygenases (LPMOs) are crucial industrial enzymes required in the biorefinery industry as well as in natural carbon cycle. These enzymes known to possess auxiliary activity are produced by numerous bacterial and fungal species to assist in the degradation of cellulosic biomass. In this study, we annotated and performed structural analysis of an uncharacterized thermostable LPMO from Penicillium funiculosum (PfLPMO9) in an attempt to understand nature of this enzyme in biomass degradation. PfLPMO9 exhibited 75% and 36% structural identity to Thermoascus aurantiacus (TaLPMO9A) and Lentinus similis (LsLPMO9A), respectively. Analysis of the molecular interactions during substrate binding revealed that PfLPMO9 demonstrated a higher binding affinity with a {Delta}G free energy of -46 k kcal/mol when compared with that of TaLPMO9A (-31 kcal/mol). The enzyme was further found to be highly thermostable at elevated temperature with a half-life of [~]88 h at 50 {degrees}C. Furthermore, multiple fungal genetic manipulation tools were employed to simultaneously overexpress this LPMO and Cellobiohydrolase I (CBH1) in catabolite derepressed strain of Penicillium funiculosum, PfMig188, in order to improve its saccharification performance towards acid pretreated wheat straw (PWS) at 20% substrate loading. The resulting transformants showed [~]200% and [~]66% increase in LPMO and Avicelase activities, respectively. While the secretomes of individually overexpressed LPMO and CBH1-strains increased saccharification of PWS by 6% and 13%, respectively, over PfMig188 at same enzyme concentration, the simultaneous overexpression of these two genes led to 20% increase in saccharification efficiency over PfMig188, which accounted for 82% saccharification of PWS at 20% substrate loading. ImportanceEnzymatic hydrolysis of cellulosic biomass by cellulases continues to be a significant bottleneck in the development of second-generation bio-based industries. While efforts are being intensified at how best to obtain indigenous cellulase for biomass hydrolysis, the high production cost of this enzyme remains a crucial challenge confronting its wide availability for efficient utilization of cellulosic materials. This is because it is challenging to get an enzymatic cocktail with balanced activity from a single host. This report provides for the first time the annotation and structural analysis of an uncharacterized thermostable lytic polysaccharide monooxygenase (LPMO) gene in Penicillium funiculosum and its impact in biomass deconstruction upon overexpression in catabolite derepressed strain of P. funiculosum. Cellobiohydrolase I (CBH1) which is the most important enzyme produced by many cellulolytic fungi for saccharification of crystalline cellulose was further overexpressed simultaneously with the LPMO. The resulting secretome was analyzed for enhanced LPMO and exocellulase activities with the corresponding improvement in its saccharification performance at high substrate loading by [~]20% using a minimal amount of protein.

microbiology↗