Effect of Drought on the Methylerythritol 4-Phosphate (MEP) Pathway in the Isoprene Emitting Conifer Picea glauca

Abstract

The methylerythritol 4-phosphate (MEP) pathway of isoprenoid biosynthesis produces chlorophyll side chains and compounds that function in resistance to abiotic stresses, including carotenoids, and isoprene. Thus we investigated the effects of moderate and severe drought on MEP pathway function in the conifer Picea glauca , a boreal species at risk under global warming trends. Although moderate drought treatment reduced the photosynthetic rate by over 70%, metabolic flux through the MEP pathway was reduced by only 37%. The activity of the putative rate-limiting step, 1-deoxy- D -xylulose-5-phosphate synthase (DXS), was also reduced by about 50%, supporting the key role of this enzyme in regulating pathway metabolic flux. However, under severe drought, as flux declined below detectable levels, DXS activity showed no significant decrease, indicating a much-reduced role in controlling flux under these conditions. Both MEP pathway intermediates and the MEP pathway product isoprene incorporate administered 13 CO 2 to high levels (75–85%) under well-watered control conditions indicating a close connection to photosynthesis. However, this incorporation declined precipitously under drought, demonstrating exploitation of alternative carbon sources. Despite the reductions in MEP pathway flux and intermediate pools, there was no detectable decline in most major MEP pathway products under drought (except for violaxanthin under moderate and severe stress and isoprene under severe stress) suggesting that the pathway is somehow buffered against this stress. The resilience of the MEP pathway under drought may be a consequence of the importance of the metabolites formed under these conditions.

Protein expression plasticity contributes to heat and drought tolerance of date palm

“…In our study, isoprene emissions were affected by water deprivation only after 14 days and later than photosynthesis (see also Kruse et al 2019 ). The effects of drought on isoprene emissions agree with the severity of the stress: emission decreases under severe but not mild drought, when it becomes partially sustained by non-photosynthetic carbon supply (Pegoraro et al 2004 , 2006 ; Brilli et al 2007 ; Perreca et al 2020 ). The resilience of emissions under limited photosynthetic capacity suggests a role of isoprene under drought.…”

Methyl Jasmonate and Methyl-β-Cyclodextrin Individually Boost Triterpenoid Biosynthesis in Chlamydomonas Reinhardtii UVM4

“…MeJA is known to trigger an oxidative stress in plants by inducing the production of ROS first in the mitochondria and subsequently in the chloroplasts [ 14 , 22 ]. Oxidative stress is one of the main causes of MEP pathway re-arrangement and up-regulation in plant cells, as certain products of this pathway (including carotenoids, tocopherols and isoprene) are involved in protection against oxidative stress [ 23 ]. Our previous study showed that MeJA up-regulated the MEP pathway in C. reinhardtii ; however, this current work brings evidence that it is doing so by prompting an oxidative stress.…”

Phytosterols in Seaweeds: An Overview on Biosynthesis to Biomedical Applications

“…Isoprene from the MEP pathway catalyzes the synthesis of monoterpenes, diterpenes, chlorophyll, carotenoids, and other phytohormones, such as gibberellin, strigolactone, and abscisic acid. It is indeed a case that the MVA pathway-derived isoprene is responsible for the synthesis of the phytosterol precursor, squalene (a triterpene), via geranyl pyrophosphate (GPP) and farnesyl pyrophosphate (FPP), which are the precursors of monoterpenes and triterpenes, respectively [ 22 , 23 ]. FPP synthase (FPPS) and squalene synthase (SQS) catalyze these sequence reactions, which follow the epoxidation of squalene into 2, 3-oxidosqualene by squalene epoxidase ( Figure 1 Bi).…”