Root isoprene formation alters lateral root development

Abstract

Isoprene is a C5 volatile organic compound, which can protect aboveground plant tissue from abiotic stress such as short-term high temperatures and accumulation of reactive oxygen species (ROS). Here, we uncover new roles for isoprene in the plant belowground tissues. By analysing Populus x canescens isoprene synthase (PcISPS) promoter reporter plants, we discovered PcISPS promoter activity in certain regions of the roots including the vascular tissue, the differentiation zone and the root cap. Treatment of roots with auxin or salt increased PcISPS promoter activity at these sites, especially in the developing lateral roots (LR). Transgenic, isoprene non-emitting poplar roots revealed an accumulation of O 2 − in the same root regions where PcISPS promoter activity was localized. Absence of isoprene emission, moreover, increased the formation of LRs. Inhibition of NAD(P)H oxidase activity suppressed LR development, suggesting the involvement of ROS in this process. The analysis of the fine root proteome revealed a constitutive shift in the amount of several redox balance, signalling and development related proteins, such as superoxide dismutase, various peroxidases and linoleate 9S-lipoxygenase, in isoprene non-emitting poplar roots. Together our results indicate for isoprene a ROS-related function, eventually co-regulating the plant-internal signalling network and development processes in root tissue.

Insights into the Intraspecific Variability of the above and Belowground Emissions of Volatile Organic Compounds in Tomato

“…The VOCs that are produced by roots can be similar to those produced by other organs or they can be organ specific. For example, isoprene, a major plant VOC typically formed in leaves of poplar, is also produced by roots albeit at much lower rates than in leaves [59]. In tomato, [34] analyzed the terpene profiles of different tissues and reported relatively high amounts of geraniol and β-phellandrene in roots, which coincides with the terpenes are that present in our root extracts.…”

Isoprene and β‐caryophyllene confer plant resistance via different plant internal signalling pathways

“…Because microbes often grow in close association with plants, the signalling distance may be shorter than in the plant–plant interactions described here. Recently, it has been shown that root‐internal isoprene can lead to changes in root architecture and redox status in certain root cells (Miloradovic van Doorn et al, 2020). For example, if epiphytic or endophytic bacteria release isoprene, the compound could lead to sensitive adjustments in plant redox balance and alter plant performance.…”

Isoprene: An Antioxidant Itself or a Molecule with Multiple Regulatory Functions in Plants?

“…With the current knowledge, it seems difficult to exclusively consider isoprene as a stress signaling molecule, since various reports relate isoprene to plant growth and development. Recent results obtained in both poplar and Arabidopsis plants have shown that IspS gene promoter activity takes place in many plant parts, including different root regions such as vascular tissue, root hairs, root cap and developing lateral roots [ 65 ]. Promoter activity was stimulated by the treatment with the growth hormone indole-3-acetic acid, and transgenic poplar plants unable to emit isoprene showed increased formation of lateral roots [ 65 ].…”

“…Recent results obtained in both poplar and Arabidopsis plants have shown that IspS gene promoter activity takes place in many plant parts, including different root regions such as vascular tissue, root hairs, root cap and developing lateral roots [ 65 ]. Promoter activity was stimulated by the treatment with the growth hormone indole-3-acetic acid, and transgenic poplar plants unable to emit isoprene showed increased formation of lateral roots [ 65 ]. Isoprene-emitting Arabidopsis plants transformed with the IspS gene from Eucalyptus globulus showed increased hypocotyl, cotyledon, leaf and inflorescence growth, suggesting that isoprene may exert its effects on growth through direct regulation of gene expression [ 51 ].…”