The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

Dinesh A Nagegowda - One of the best experts on this subject based on the ideXlab platform.

  • a wrky transcription factor from withania somnifera regulates triterpenoid withanolide accumulation and Biotic Stress tolerance through modulation of phytosterol and defense pathways
    New Phytologist, 2017
    Co-Authors: Anup Kumar Singh, Sarma Rajeev Kumar, Varun Dwivedi, Avanish Rai, Shaifali Pal, Ajit Kumar Shasany, Dinesh A Nagegowda
    Abstract:

    Summary Withania somnifera produces pharmacologically important triterpenoid withanolides that are derived via phytosterol pathway; however, their biosynthesis and regulation remain to be elucidated. A jasmonate- and salicin-inducible WRKY transcription factor from W. somnifera (WsWRKY1) exhibiting correlation with withaferin A accumulation was functionally characterized employing virus-induced gene silencing and overexpression studies combined with transcript and metabolite analyses, and chromatin immunoprecipitation assay. WsWRKY1 silencing resulted in stunted plant growth, reduced transcripts of phytosterol pathway genes with corresponding reduction in phytosterols and withanolides in W. somnifera. Its overexpression elevated the biosynthesis of triterpenoids in W. somnifera (phytosterols and withanolides), as well as tobacco and tomato (phytosterols). Moreover, WsWRKY1 binds to W-box sequences in promoters of W. somnifera genes encoding squalene synthase and squalene epoxidase, indicating its direct regulation of triterpenoid pathway. Furthermore, while WsWRKY1 silencing in W. somnifera compromised the tolerance to bacterial growth, fungal infection, and insect feeding, its overexpression in tobacco led to improved Biotic Stress tolerance. Together these findings demonstrate that WsWRKY1 has a positive regulatory role on phytosterol and withanolides biosynthesis, and defense against Biotic Stress, highlighting its importance as a metabolic engineering tool for simultaneous improvement of triterpenoid biosynthesis and plant defense.

  • virus induced gene silencing of withania somnifera squalene synthase negatively regulates sterol and defence related genes resulting in reduced withanolides and Biotic Stress tolerance
    Plant Biotechnology Journal, 2015
    Co-Authors: Anup Kumar Singh, Varun Dwivedi, Avanish Rai, Shaifali Pal, Ajit Kumar Shasany, Sajjalavarahalli Gangireddy Eswara Reddy, Dodaghatta Krishnarao Venkata Rao, Dinesh A Nagegowda
    Abstract:

    Summary Withania somnifera (L.) Dunal is an important Indian medicinal plant that produces withanolides, which are triterpenoid steroidal lactones having diverse biological activities. To enable fast and efficient functional characterization of genes in this slow-growing and difficult-to-transform plant, a virus-induced gene silencing (VIGS) was established by silencing phytoene desaturase (PDS) and squalene synthase (SQS). VIGS of the gene encoding SQS, which provides precursors for triterpenoids, resulted in significant reduction of squalene and withanolides, demonstrating its application in studying withanolides biosynthesis in W. somnifera leaves. A comprehensive analysis of gene expression and sterol pathway intermediates in WsSQS-vigs plants revealed transcriptional modulation with positive feedback regulation of mevalonate pathway genes, and negative feed-forward regulation of downstream sterol pathway genes including DWF1 (delta-24-sterol reductase) and CYP710A1 (C-22-sterol desaturase), resulting in significant reduction of sitosterol, campesterol and stigmasterol. However, there was little effect of SQS silencing on cholesterol, indicating the contribution of sitosterol, campesterol and stigmasterol, but not of cholesterol, towards withanolides formation. Branch-point oxidosqualene synthases in WsSQS-vigs plants exhibited differential regulation with reduced CAS (cycloartenol synthase) and cycloartenol, and induced BAS (bamyrin synthase) and b-amyrin. Moreover, SQS silencing also led to the down-regulation of brassinosteroid-6-oxidase-2 (BR6OX2), pathogenesis-related (PR) and nonexpressor of PR (NPR) genes, resulting in reduced tolerance to bacterial and fungal infection as well as to insect feeding. Taken together, SQS silencing negatively regulated sterol and defence-related genes leading to reduced phytosterols, withanolides and Biotic Stress tolerance, thus implicating the application of VIGS for functional analysis of genes related to withanolides formation in W. somnifera leaves.

Raquel Lia Chan - One of the best experts on this subject based on the ideXlab platform.

  • hahb10 a sunflower hd zip ii transcription factor participates in the induction of flowering and in the control of phytohormone mediated responses to Biotic Stress
    Journal of Experimental Botany, 2011
    Co-Authors: Carlos A Dezar, Pablo A Manavella, Gustavo Bonaventure, Ian T Baldwin, Jorge Ignacio Giacomelli, Marcio Alvesferreira, Raquel Lia Chan
    Abstract:

    The transcription factor HAHB10 belongs to the sunflower (Helianthus annuus) HD-Zip II subfamily and it has been previously associated with the induction of flowering. In this study it is shown that HAHB10 is expressed in sunflower leaves throughout the vegetative stage and in stamens during the reproductive stage. In short-day inductive conditions the expression of this gene is induced in shoot apexes together with the expression of the flowering genes HAFT and HAAP1. Transgenic Arabidopsis plants expressing HAHB10 cDNA under regulation either by its own promoter or by cauliflower mosaic virus (CaMV) 35S exhibited an early flowering phenotype. This phenotype was completely reverted in a non-inductive light regime, indicating a photoperiod-dependent action for this transcription factor. Gene expression profiling of Arabidopsis plants constitutively expressing HAHB10 indicated that specific flowering transition genes such as FT, FUL ,a ndSEP3 were induced several fold, whereas genes related to Biotic Stress responses, such asPR1, PR2, ICS1, AOC1, EDS5 ,a ndPDF1-2a, were repressed. The expression of HAHB10 and of the flowering genes HASEP3 and HAFT was up-regulated by both salicylic acid (SA) treatment and infection with a virulent strain of Pseudomonas syringae. Basal SA and jasmonic acid (JA) levels in Arabidopsis plants ectopically expressing HAHB10 were similar to those of control plants; however, SA levels differentially increased in the transgenic plants after wounding and infection with P. syringae while JA levels differentially decreased. Taken together, the results indicated that HAHB10 participates in two different processes in plants: the transition from the vegetative to the flowering stage via the induction of specific flowering transition genes and the accumulation of phytohormones upon Biotic Stresses.

  • hahb4 a sunflower hd zip protein integrates signals from the jasmonic acid and ethylene pathways during wounding and Biotic Stress responses
    Plant Journal, 2008
    Co-Authors: Pablo A Manavella, Carlos A Dezar, Gustavo Bonaventure, Ian T Baldwin, Raquel Lia Chan
    Abstract:

    The Helianthus annuus (sunflower) HAHB4 transcription factor belongs to the HD-Zip family and its transcript levels are strongly induced when sunflower plants are attacked by herbivores, mechanically damaged or treated with methyl-jasmonic acid (MeJA) or ethylene (ET). Promoter fusion analysis, in Arabidopsis and in sunflower, demonstrated that induction of HAHB4 expression by these treatments is regulated at the transcriptional level. In transiently transformed sunflower plants HAHB4 expression upregulates the transcript levels of several genes involved in JA biosynthesis and defense-related processes such as the production of green leaf volatiles and trypsin protease inhibitors (TPI). In HAHB4 sunflower overexpressing tissue, increased activities of lipoxygenase, hydroperoxide lyase and TPI are detected whereas in HAHB4-silenced tissue these activities are reduced. Transgenic Arabidopsis thaliana and Zea mays plants ecotopically expressing HAHB4 also exhibit higher transcript levels of defense-related genes and when Spodoptera littoralis or Spodoptera frugiperda larvae are placed on each species, respectively, larvae consumed less and gain less mass compared with larvae feeding on control plants. Arabidopsis plants ectopically expressing HAHB4 had higher amounts of JA, JA-isoleucine and ET compared with control plants both before and after wounding, but reduced levels of salicylic acid (SA) after wounding and bacterial infection. We conclude that HAHB4 coordinates the production of phytohormones during Biotic Stress responses and mechanical damage, specifically by positively regulating JA and ET production and negatively regulating ET sensitivity and SA accumulation.

Anup Kumar Singh - One of the best experts on this subject based on the ideXlab platform.

  • a wrky transcription factor from withania somnifera regulates triterpenoid withanolide accumulation and Biotic Stress tolerance through modulation of phytosterol and defense pathways
    New Phytologist, 2017
    Co-Authors: Anup Kumar Singh, Sarma Rajeev Kumar, Varun Dwivedi, Avanish Rai, Shaifali Pal, Ajit Kumar Shasany, Dinesh A Nagegowda
    Abstract:

    Summary Withania somnifera produces pharmacologically important triterpenoid withanolides that are derived via phytosterol pathway; however, their biosynthesis and regulation remain to be elucidated. A jasmonate- and salicin-inducible WRKY transcription factor from W. somnifera (WsWRKY1) exhibiting correlation with withaferin A accumulation was functionally characterized employing virus-induced gene silencing and overexpression studies combined with transcript and metabolite analyses, and chromatin immunoprecipitation assay. WsWRKY1 silencing resulted in stunted plant growth, reduced transcripts of phytosterol pathway genes with corresponding reduction in phytosterols and withanolides in W. somnifera. Its overexpression elevated the biosynthesis of triterpenoids in W. somnifera (phytosterols and withanolides), as well as tobacco and tomato (phytosterols). Moreover, WsWRKY1 binds to W-box sequences in promoters of W. somnifera genes encoding squalene synthase and squalene epoxidase, indicating its direct regulation of triterpenoid pathway. Furthermore, while WsWRKY1 silencing in W. somnifera compromised the tolerance to bacterial growth, fungal infection, and insect feeding, its overexpression in tobacco led to improved Biotic Stress tolerance. Together these findings demonstrate that WsWRKY1 has a positive regulatory role on phytosterol and withanolides biosynthesis, and defense against Biotic Stress, highlighting its importance as a metabolic engineering tool for simultaneous improvement of triterpenoid biosynthesis and plant defense.

  • virus induced gene silencing of withania somnifera squalene synthase negatively regulates sterol and defence related genes resulting in reduced withanolides and Biotic Stress tolerance
    Plant Biotechnology Journal, 2015
    Co-Authors: Anup Kumar Singh, Varun Dwivedi, Avanish Rai, Shaifali Pal, Ajit Kumar Shasany, Sajjalavarahalli Gangireddy Eswara Reddy, Dodaghatta Krishnarao Venkata Rao, Dinesh A Nagegowda
    Abstract:

    Summary Withania somnifera (L.) Dunal is an important Indian medicinal plant that produces withanolides, which are triterpenoid steroidal lactones having diverse biological activities. To enable fast and efficient functional characterization of genes in this slow-growing and difficult-to-transform plant, a virus-induced gene silencing (VIGS) was established by silencing phytoene desaturase (PDS) and squalene synthase (SQS). VIGS of the gene encoding SQS, which provides precursors for triterpenoids, resulted in significant reduction of squalene and withanolides, demonstrating its application in studying withanolides biosynthesis in W. somnifera leaves. A comprehensive analysis of gene expression and sterol pathway intermediates in WsSQS-vigs plants revealed transcriptional modulation with positive feedback regulation of mevalonate pathway genes, and negative feed-forward regulation of downstream sterol pathway genes including DWF1 (delta-24-sterol reductase) and CYP710A1 (C-22-sterol desaturase), resulting in significant reduction of sitosterol, campesterol and stigmasterol. However, there was little effect of SQS silencing on cholesterol, indicating the contribution of sitosterol, campesterol and stigmasterol, but not of cholesterol, towards withanolides formation. Branch-point oxidosqualene synthases in WsSQS-vigs plants exhibited differential regulation with reduced CAS (cycloartenol synthase) and cycloartenol, and induced BAS (bamyrin synthase) and b-amyrin. Moreover, SQS silencing also led to the down-regulation of brassinosteroid-6-oxidase-2 (BR6OX2), pathogenesis-related (PR) and nonexpressor of PR (NPR) genes, resulting in reduced tolerance to bacterial and fungal infection as well as to insect feeding. Taken together, SQS silencing negatively regulated sterol and defence-related genes leading to reduced phytosterols, withanolides and Biotic Stress tolerance, thus implicating the application of VIGS for functional analysis of genes related to withanolides formation in W. somnifera leaves.

Carlos A Dezar - One of the best experts on this subject based on the ideXlab platform.

  • hahb10 a sunflower hd zip ii transcription factor participates in the induction of flowering and in the control of phytohormone mediated responses to Biotic Stress
    Journal of Experimental Botany, 2011
    Co-Authors: Carlos A Dezar, Pablo A Manavella, Gustavo Bonaventure, Ian T Baldwin, Jorge Ignacio Giacomelli, Marcio Alvesferreira, Raquel Lia Chan
    Abstract:

    The transcription factor HAHB10 belongs to the sunflower (Helianthus annuus) HD-Zip II subfamily and it has been previously associated with the induction of flowering. In this study it is shown that HAHB10 is expressed in sunflower leaves throughout the vegetative stage and in stamens during the reproductive stage. In short-day inductive conditions the expression of this gene is induced in shoot apexes together with the expression of the flowering genes HAFT and HAAP1. Transgenic Arabidopsis plants expressing HAHB10 cDNA under regulation either by its own promoter or by cauliflower mosaic virus (CaMV) 35S exhibited an early flowering phenotype. This phenotype was completely reverted in a non-inductive light regime, indicating a photoperiod-dependent action for this transcription factor. Gene expression profiling of Arabidopsis plants constitutively expressing HAHB10 indicated that specific flowering transition genes such as FT, FUL ,a ndSEP3 were induced several fold, whereas genes related to Biotic Stress responses, such asPR1, PR2, ICS1, AOC1, EDS5 ,a ndPDF1-2a, were repressed. The expression of HAHB10 and of the flowering genes HASEP3 and HAFT was up-regulated by both salicylic acid (SA) treatment and infection with a virulent strain of Pseudomonas syringae. Basal SA and jasmonic acid (JA) levels in Arabidopsis plants ectopically expressing HAHB10 were similar to those of control plants; however, SA levels differentially increased in the transgenic plants after wounding and infection with P. syringae while JA levels differentially decreased. Taken together, the results indicated that HAHB10 participates in two different processes in plants: the transition from the vegetative to the flowering stage via the induction of specific flowering transition genes and the accumulation of phytohormones upon Biotic Stresses.

  • hahb4 a sunflower hd zip protein integrates signals from the jasmonic acid and ethylene pathways during wounding and Biotic Stress responses
    Plant Journal, 2008
    Co-Authors: Pablo A Manavella, Carlos A Dezar, Gustavo Bonaventure, Ian T Baldwin, Raquel Lia Chan
    Abstract:

    The Helianthus annuus (sunflower) HAHB4 transcription factor belongs to the HD-Zip family and its transcript levels are strongly induced when sunflower plants are attacked by herbivores, mechanically damaged or treated with methyl-jasmonic acid (MeJA) or ethylene (ET). Promoter fusion analysis, in Arabidopsis and in sunflower, demonstrated that induction of HAHB4 expression by these treatments is regulated at the transcriptional level. In transiently transformed sunflower plants HAHB4 expression upregulates the transcript levels of several genes involved in JA biosynthesis and defense-related processes such as the production of green leaf volatiles and trypsin protease inhibitors (TPI). In HAHB4 sunflower overexpressing tissue, increased activities of lipoxygenase, hydroperoxide lyase and TPI are detected whereas in HAHB4-silenced tissue these activities are reduced. Transgenic Arabidopsis thaliana and Zea mays plants ecotopically expressing HAHB4 also exhibit higher transcript levels of defense-related genes and when Spodoptera littoralis or Spodoptera frugiperda larvae are placed on each species, respectively, larvae consumed less and gain less mass compared with larvae feeding on control plants. Arabidopsis plants ectopically expressing HAHB4 had higher amounts of JA, JA-isoleucine and ET compared with control plants both before and after wounding, but reduced levels of salicylic acid (SA) after wounding and bacterial infection. We conclude that HAHB4 coordinates the production of phytohormones during Biotic Stress responses and mechanical damage, specifically by positively regulating JA and ET production and negatively regulating ET sensitivity and SA accumulation.

Shaifali Pal - One of the best experts on this subject based on the ideXlab platform.

  • a wrky transcription factor from withania somnifera regulates triterpenoid withanolide accumulation and Biotic Stress tolerance through modulation of phytosterol and defense pathways
    New Phytologist, 2017
    Co-Authors: Anup Kumar Singh, Sarma Rajeev Kumar, Varun Dwivedi, Avanish Rai, Shaifali Pal, Ajit Kumar Shasany, Dinesh A Nagegowda
    Abstract:

    Summary Withania somnifera produces pharmacologically important triterpenoid withanolides that are derived via phytosterol pathway; however, their biosynthesis and regulation remain to be elucidated. A jasmonate- and salicin-inducible WRKY transcription factor from W. somnifera (WsWRKY1) exhibiting correlation with withaferin A accumulation was functionally characterized employing virus-induced gene silencing and overexpression studies combined with transcript and metabolite analyses, and chromatin immunoprecipitation assay. WsWRKY1 silencing resulted in stunted plant growth, reduced transcripts of phytosterol pathway genes with corresponding reduction in phytosterols and withanolides in W. somnifera. Its overexpression elevated the biosynthesis of triterpenoids in W. somnifera (phytosterols and withanolides), as well as tobacco and tomato (phytosterols). Moreover, WsWRKY1 binds to W-box sequences in promoters of W. somnifera genes encoding squalene synthase and squalene epoxidase, indicating its direct regulation of triterpenoid pathway. Furthermore, while WsWRKY1 silencing in W. somnifera compromised the tolerance to bacterial growth, fungal infection, and insect feeding, its overexpression in tobacco led to improved Biotic Stress tolerance. Together these findings demonstrate that WsWRKY1 has a positive regulatory role on phytosterol and withanolides biosynthesis, and defense against Biotic Stress, highlighting its importance as a metabolic engineering tool for simultaneous improvement of triterpenoid biosynthesis and plant defense.

  • virus induced gene silencing of withania somnifera squalene synthase negatively regulates sterol and defence related genes resulting in reduced withanolides and Biotic Stress tolerance
    Plant Biotechnology Journal, 2015
    Co-Authors: Anup Kumar Singh, Varun Dwivedi, Avanish Rai, Shaifali Pal, Ajit Kumar Shasany, Sajjalavarahalli Gangireddy Eswara Reddy, Dodaghatta Krishnarao Venkata Rao, Dinesh A Nagegowda
    Abstract:

    Summary Withania somnifera (L.) Dunal is an important Indian medicinal plant that produces withanolides, which are triterpenoid steroidal lactones having diverse biological activities. To enable fast and efficient functional characterization of genes in this slow-growing and difficult-to-transform plant, a virus-induced gene silencing (VIGS) was established by silencing phytoene desaturase (PDS) and squalene synthase (SQS). VIGS of the gene encoding SQS, which provides precursors for triterpenoids, resulted in significant reduction of squalene and withanolides, demonstrating its application in studying withanolides biosynthesis in W. somnifera leaves. A comprehensive analysis of gene expression and sterol pathway intermediates in WsSQS-vigs plants revealed transcriptional modulation with positive feedback regulation of mevalonate pathway genes, and negative feed-forward regulation of downstream sterol pathway genes including DWF1 (delta-24-sterol reductase) and CYP710A1 (C-22-sterol desaturase), resulting in significant reduction of sitosterol, campesterol and stigmasterol. However, there was little effect of SQS silencing on cholesterol, indicating the contribution of sitosterol, campesterol and stigmasterol, but not of cholesterol, towards withanolides formation. Branch-point oxidosqualene synthases in WsSQS-vigs plants exhibited differential regulation with reduced CAS (cycloartenol synthase) and cycloartenol, and induced BAS (bamyrin synthase) and b-amyrin. Moreover, SQS silencing also led to the down-regulation of brassinosteroid-6-oxidase-2 (BR6OX2), pathogenesis-related (PR) and nonexpressor of PR (NPR) genes, resulting in reduced tolerance to bacterial and fungal infection as well as to insect feeding. Taken together, SQS silencing negatively regulated sterol and defence-related genes leading to reduced phytosterols, withanolides and Biotic Stress tolerance, thus implicating the application of VIGS for functional analysis of genes related to withanolides formation in W. somnifera leaves.