A WRKY transcription factor from Withania somnifera regulates triterpenoid withanolide accumulation and biotic stress tolerance through modulation of phytosterol and defense pathways

作者：Singh Anup Kumar; Kumar Sarma Rajeev; Dwivedi Varun; Rai Avanish; Pal Shaifali; Shasany Ajit K; Nagegowda Dinesh A

来源：NEW PHYTOLOGIST, 2017, 215(3): 1115-1131.

DOI：10.1111/nph.14663

<jats:title>Summary</jats:title><jats:p>
<jats:list list-type="bullet">

<jats:list-item><jats:p><jats:italic>Withania somnifera</jats:italic> produces pharmacologically important triterpenoid withanolides that are derived via phytosterol pathway; however, their biosynthesis and regulation remain to be elucidated.</jats:p></jats:list-item>

<jats:list-item><jats:p>A jasmonate‐ and salicin‐inducible <jats:styled-content style="fixed-case">WRKY</jats:styled-content> transcription factor from <jats:italic>W. somnifera</jats:italic> (<jats:italic>Ws<jats:styled-content style="fixed-case">WRKY</jats:styled-content>1</jats:italic>) 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.</jats:p></jats:list-item>

<jats:list-item><jats:p><jats:italic>Ws<jats:styled-content style="fixed-case">WRKY</jats:styled-content>1</jats:italic> silencing resulted in stunted plant growth, reduced transcripts of phytosterol pathway genes with corresponding reduction in phytosterols and withanolides in <jats:italic>W. somnifera</jats:italic>. Its overexpression elevated the biosynthesis of triterpenoids in <jats:italic>W. somnifera</jats:italic> (phytosterols and withanolides), as well as tobacco and tomato (phytosterols). Moreover, Ws<jats:styled-content style="fixed-case">WRKY</jats:styled-content>1 binds to W‐box sequences in promoters of <jats:italic>W. somnifera</jats:italic> genes encoding squalene synthase and squalene epoxidase, indicating its direct regulation of triterpenoid pathway. Furthermore, while <jats:italic>Ws<jats:styled-content style="fixed-case">WRKY</jats:styled-content>1</jats:italic> silencing in <jats:italic>W. somnifera</jats:italic> compromised the tolerance to bacterial growth, fungal infection, and insect feeding, its overexpression in tobacco led to improved biotic stress tolerance.</jats:p></jats:list-item>

<jats:list-item><jats:p>Together these findings demonstrate that <jats:italic>Ws<jats:styled-content style="fixed-case">WRKY</jats:styled-content>1</jats:italic> 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.</jats:p></jats:list-item>
</jats:list>
</jats:p>

• 出版日期2017-8