New Insights on the Regulation of Glucosinolate Biosynthesis via COP1 and DELLA Proteins in Arabidopsis Thaliana.

Henning Frerigmann,Tamara Gigolashvili,Ute Hoecker

doi:10.3389/fpls.2021.680255

Abstract

The biosynthesis of defensive secondary metabolites, such as glucosinolates (GSLs), is a costly process, which requires nutrients, ATP, and reduction equivalents, and, therefore, needs well-orchestrated machinery while coordinating defense and growth. We discovered that the key repressor of light signaling, the CONSTITUTIVE PHOTOMORPHOGENIC 1/SUPPRESSOR OF PHYTOCHROME A-105 (COP1/SPA) complex, is a crucial component of GSL biosynthesis regulation. Various mutants in this COP1/SPA complex exhibited a strongly reduced level of GSL and a low expression of jasmonate (JA)-dependent genes. Furthermore, cop1, which is known to accumulate DELLA proteins in the dark, shows reduced gibberellin (GA) and JA signaling, thereby phenocopying other DELLA-accumulating mutants. This phenotype can be complemented by a dominant gain-of-function allele of MYC3 and by crossing with a mutant having low DELLA protein levels. Hence, SPA1 interacts with DELLA proteins in a yeast two-hybrid screen, whereas high levels of DELLA inhibit MYC function and suppress JA signaling. DELLA accumulation leads to reduced synthesis of GSL and inhibited growth. Thus, the COP1/SPA-mediated degradation of DELLA not only affects growth but also regulates the biosynthesis of GSLs.

Highlights

Recent years have seen the reintroduction of ecological theories, focusing on the interplay between growth and immunity, into studies on molecular plant biology (Züst et al, 2011; Yang et al, 2012; Campos et al, 2016; Kliebenstein, 2016; Major et al, 2020)
Because many phyB-mediated effects are transmitted via the action of the main repressor of light signaling, the COP1/SPA complex, this prompted an investigation on the role of this complex in the production of defense compounds
By catalyzing the formation of a sulfated JA derivative, ST2a acts to degrade bioactive forms of JA and represents another molecular link between photoreceptors and hormone signaling in plants. We have uncovered another crucial component of the hardwired hormone-linked transcriptional network upstream from the MYC–bHLH transcription factors (TFs) complex, which regulates the production of defensive GSL compounds (Figure 1; Supplementary Figure 7)

Summary

Introduction

Recent years have seen the reintroduction of ecological theories, focusing on the interplay between growth and immunity, into studies on molecular plant biology (Züst et al, 2011; Yang et al, 2012; Campos et al, 2016; Kliebenstein, 2016; Major et al, 2020). While the knowledge on the regulation of defense metabolites is further expanded, the coordination of synthesis of these compounds with other needs of plants still requires more attention. Jasmonate (JA) coordinates immune and growth responses to increase plant survival upon changing environmental cues. The presence of other plants competing for light [sensed by a low red (R) to far-red (FR) light ratio] triggers rapid elongation growth and consumes metabolic resources that could otherwise be invested in the production of defense compounds. The phytohormones JA and gibberellin (GA) are fundamentally important in facilitating the rapid adjustment of plant responses to the changing environment (Hou et al, 2013) Plants have evolved adaptation mechanisms for mediating the balance in the “dilemma to grow or defend.” The phytohormones JA and gibberellin (GA) are fundamentally important in facilitating the rapid adjustment of plant responses to the changing environment (Hou et al, 2013)

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Discussion

Conclusion