Regulation of dhurrin pathway gene expression during Sorghum\xa0bicolor development

Roslyn M Gleadow,John E Mullet,Cecilia K Blomstedt,Birger Lindberg Møller,Brian A Mckinley,Austin C Lamb

doi:10.1007/s00425-021-03774-2

Roslyn M Gleadow, John E Mullet + Show 4 more

Open Access

https://doi.org/10.1007/s00425-021-03774-2

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Abstract

Main conclusionDevelopmental and organ-specific expression of genes in dhurrin biosynthesis, bio-activation, and recycling offers dynamic metabolic responses optimizing growth and defence responses in Sorghum.Plant defence models evaluate the costs and benefits of resource investments at different stages in the life cycle. Poor understanding of the molecular regulation of defence deployment and remobilization hampers accuracy of the predictions. Cyanogenic glucosides, such as dhurrin are phytoanticipins that release hydrogen cyanide upon bio-activation. In this study, RNA-seq was used to investigate the expression of genes involved in the biosynthesis, bio-activation and recycling of dhurrin in Sorghum bicolor. Genes involved in dhurrin biosynthesis were highly expressed in all young developing vegetative tissues (leaves, leaf sheath, roots, stems), tiller buds and imbibing seeds and showed gene specific peaks of expression in leaves during diel cycles. Genes involved in dhurrin bio-activation were expressed early in organ development with organ-specific expression patterns. Genes involved in recycling were expressed at similar levels in the different organ during development, although post-floral initiation when nutrients are remobilized for grain filling, expression of GSTL1 decreased > tenfold in leaves and NITB2 increased > tenfold in stems. Results are consistent with the establishment of a pre-emptive defence in young tissues and regulated recycling related to organ senescence and increased demand for nitrogen during grain filling. This detailed characterization of the transcriptional regulation of dhurrin biosynthesis, bioactivation and remobilization genes during organ and plant development will aid elucidation of gene regulatory networks and signalling pathways that modulate gene expression and dhurrin levels. In-depth knowledge of dhurrin metabolism could improve the yield, nitrogen use efficiency and stress resilience of Sorghum.

Highlights

Ontogenetic trajectories in defence have been described in hundreds of species of plants
Data on the expression of genes involved in dhurrin biosynthesis (CYP79A1, CYP71E1, UGT85B1 and POR), bioactivation (DHR1, DHR2, DHR-like3, DHR-like4; hydroxynitrile lyase (HNL)), prevention of auto-toxicity (CAS, NIT) and endogenous recycling (GST lambda candidates and NIT4A/NIT4B2) during organ and plant development are presented
We analysed the expression of SbMATE2, which has been shown to transport dhurrin (Darbani et al 2016) and a candidate nitrate/peptide family (NPF) transporter (SbCGTR1) that is the closest sorghum homolog of a transporter identified in cassava, Fig. 4 Variation in leaf hydrogen cyanide potential (HCNp) among four S. bicolor BTx623 individuals

Summary

Introduction

Ontogenetic trajectories in defence have been described in hundreds of species of plants. As with many chemical defence systems, the costs of deployment in terms of a growth sacrifice are small, and usually only detectable under resource-limiting conditions, if at all (Blomstedt et al 2018; Simon et al 2010; Sohail et al 2020; Gershenzon 1989). This lack of apparent cost could be because the costs of production are tiny (Gershenzon 1989) or off-set by other metabolic or physiological benefits (Neilson et al 2013)

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