Plant volatiles as regulators of hormone homeostasis

Abstract

Summary Some canonical plant hormones such as auxins and gibberellins have precursors that are biogenic volatiles (indole, indole acetonitrile, phenylacetaldoxime and ent‐kaurene). Cytokinins, abscisic acid and strigolactones are hormones comprising chemical moieties that have distinct volatile analogues, and are synthesised alongside constitutively emitted volatiles (isoprene, sesquiterpenes, lactones, benzenoids and apocarotenoid volatiles). Nonvolatile hormone analogues and biogenic volatile organic compounds (BVOCs) evolved in tandem as growth and behavioural regulators in unicellular organisms. In plants, however, nonvolatile hormones evolved as regulators of growth, development and differentiation, while endogenous BVOCs (often synthesised lifelong) became subtle regulators of hormone synthesis, availability, activity and turnover, all supported by functionally redundant components of hormone metabolism. Reciprocal changes in the abundance and activity of hormones, nitric oxide, and constitutive plant volatiles constantly bridge retrograde and anterograde signalling to maintain hormone equilibria even in unstressed plants. This is distinct from transient interference in hormone signalling by stress‐induced and exogenously received volatiles.

Isoprene-Emitting Tobacco Plants Are Less Affected by Moderate Water Deficit under Future Climate Change Scenario and Show Adjustments of Stress-Related Proteins in Actual Climate

“…Specifically, we speculate that the capacity to emit isoprene: (i) might have reduced the impact of WS on the proteome; and (ii) might have changed the proteomic profile, particularly contributing to the activation of specific pathways that help isoprene emitting plants to cope with stress under future climate conditions. This second effect, in particular, supports a much wider regulatory role of isoprene, as also indicated in recent works [ 34 , 44 , 45 ].…”

Isoprene enhances leaf cytokinin metabolism and induces early senescence

“…A key distinction is that continuous endogenous emission (and not exogenous exposure) incurs metabolic costs to the emitter, which may directly affect organellar carbon and energy status and hormone synthesis (our study) and also hormone‐mediated signalling (various studies). We anticipate that other endogenous volatiles, which are so far purely implicated in stress mitigation and inter‐organismal communication, will have significant interactions with canonical hormone‐mediated developmental pathways in unstressed plants (Dani & Loreto, 2022 ). Future experiments involving mutants of CK synthesis and signalling will shed more light on specific mechanisms of interference from isoprene and other biogenic volatiles in CK‐mediated changes in leaf and plant metabolism.…”

Short-term severe drought influences root volatile biosynthesis in eastern white pine (Pinus strobus L)

“…Notably, the production of isoprene and terpenoids is stimulated by jasmonic acid (JA) in plants ( Tanaka et al., 2014 ). Interestingly, the JA and salicylic acid (SA) responsive signalling cascades mediated by JASMONATE ZIM DOMAIN PROTEIN (JAZ) and MYC2 transcription factors can enhance the emission of constitutively emitted isoprene, monoterpenes and sesquiterpenes, which may upregulate stress-specific hormonal signaling ( Yang et al., 2019 ; Dani and Loreto, 2022 ). Therefore, it will be interesting to study the crosstalk among phytohormones associated with the synthesis of root VOCs in P. strobus seedlings, especially the pathway existing between terpene synthesis and ABA response under water-deficit conditions.…”