Data from: Hydroxymethylbutenyl diphosphate accumulation reveals MEP pathway regulation for high CO2induced suppression of isoprene emission
Data files
Sep 11, 2023 version files 370.09 KB

Fig_1A.csv

Fig_1B.csv

Fig_2A_B_C.csv

Fig_2D_E_F.csv

Fig_3B_D.csv

Fig_3C.csv

Fig_4.csv

Fig_S1A_B.csv

Fig_S2A_B_C_D.csv

Fig_S4.csv

Fig_S5.csv

Fig_S6.csv

README.md

Table_1.csv
Abstract
Isoprene is emitted by some plants and is the most abundant biogenic hydrocarbon entering the atmosphere. Multiple studies have elucidated protective roles of isoprene against several environmental stresses, including high temperature, excessive ozone, and herbivory attack. However, isoprene emission adversely affects atmospheric chemistry by contributing to ozone production and aerosol formation. Thus, understanding the regulation of isoprene emission in response to varying environmental conditions, for example elevated CO_{2}, is critical to comprehend how plants will respond to climate change. Isoprene emission decreases with increasing CO_{2} concentration; however, the underlying mechanism of this response is currently unknown. We demonstrated that highCO_{2}mediated suppression of isoprene emission is independent of photosynthesis and light intensity, but it is reduced with increasing temperature. Furthermore, we measured methylerythritol 4phosphate pathway metabolites in poplar leaves harvested at ambient and high CO_{2} to identify why isoprene emission is reduced under high CO_{2}. We found that hydroxymethylbutenyl diphosphate (HMBDP) was increased and dimethylallyl diphosphate (DMADP) decreased at high CO_{2}. This implies that high CO_{2} impeded the conversion of HMBDP to DMADP, possibly through the inhibition of HMBDP reductase activity, resulting in reduced isoprene emission. We further demonstrated that although this phenomenon appears similar to ABAdependent stomatal regulation, it is unrelated as abscisic acid treatment did not alter the effect of elevated CO_{2} on the suppression of isoprene emission. Thus, this study provides a comprehensive understanding of the regulation of the MEP pathway and isoprene emission in the face of increasing CO_{2}.
README: Title of Dataset: Hydroxymethylbutenyl diphosphate accumulation reveals MEP pathway regulation for high CO2induced suppression of isoprene emission
Give a brief summary of dataset contents, contextualized in experimental procedures and results.
This dataset contains
 Isoprene emission data from poplar leaves measured using the Fast Isoprene Sensor
 Assimilation rates or photosynthesis (A), intercellular CO2 concentration (Ci), and stomatal conductance (gsw) measured using LICOR 6800
 MEP pathway metabolite levels measured by LCMS/MS
Using these data, we showed that the decline in isoprene emission at high CO2 is due to accumulation of HMBDP which is an upstream precursor and reduction in DMADP, an immediate precursor of isoprene. We also showed that the CO2 responsiveness of isoprene is independent of the ABAdependent stomatal signaling pathway. Furthermore, high CO2 mediated suppression of isoprene emission is independent of varying light intensities but decreases at high temperature.
Description of the data and file structure
Raw data that were used to make the plots are provided as individual .csv files and each file name contains the figure number.
*Fig 1A. Isoprene emission measured at an interval of 1 min over 48 min as CO2 partial pressure is changed from 39 Pa to 78 Pa and back to 39 Pa
*Fig 1B. Isoprene emission measured in 14 poplar leaves at 39 Pa CO2 and 78 Pa CO2. Relative change in isoprene emission between 39 Pa and 78 Pa CO2 is calculated for each leaf.
 Mean: Mean of isoprene emission at 39 Pa and 78 Pa CO2
 SD: standard deviation
 pvalue: calculated by Student's ttest (2 tailed, paired) <br> *Fig 2A,B,C. Isoprene emission measured at 39 Pa and 78 Pa CO2 under light intensities of 1000 umol m2 s1, 750 umol m2 s1, 500 umol m2 s1, 250 umol m2 s1, and 100 umol m2 s1.
 Absolute change: Difference in isoprene emission between 39 Pa and 78 Pa CO2
 Relative change: Difference in isoprene emission between 39 Pa and 78 Pa CO2 relative to isoprene emission at 39 Pa CO2, expressed in percent
 Mean: Mean of absolute change and relative change in isoprene emission at 39 Pa and 78 Pa CO2
 SD: standard deviation
 pvalue: calculated by Student's ttest (2 tailed, paired) between isoprene emission at 39 Pa and 78 Pa CO2 *Fig 2D,E,F. Isoprene emission measured at 39 Pa and 78 Pa CO2 under temperatures 25degC, 30degC, and 35degC
 Absolute change: Difference in isoprene emission between 39 Pa and 78 Pa CO2
 Relative change: Difference in isoprene emission between 39 Pa and 78 Pa CO2 relative to isoprene emission at 39 Pa CO2, expressed in percent
 Mean: Mean of absolute change and relative change in isoprene emission at 39 Pa and 78 Pa CO2
 SD: standard deviation
 pvalue: calculated by Student's ttest (2 tailed, paired) between isoprene emission at 39 Pa and 78 Pa CO2 *Fig 3B,D. Levels of MEP pathway metabolites DXP, MEP, CDPME, MEcDP, and HMBDP in 4 biological replicates R1, R2, R3, and R4 collected at time points (i) at 39 Pa CO2 after isoprene emission has stabilized; T1 (ii) 3 min after changing CO2 to 78 Pa; T2 (iii) at 78 Pa CO2 after isoprene emission had stabilized; T3 (iv) 3 min after changing CO2 back to 39 Pa; T4 (v) at 39 Pa CO2 after isoprene emission has stabilized; T5. Each metabolite concentration is normalized to concentration of DXP. Mean: Mean of 34 biological replicates at each time point
 SD: standard deviation *Fig 3C.DMADP measured by integrating isoprene emission after lights were turned off in 3 biological replicates R1, R2, and R3 at time points (i) at 39 Pa CO2 after isoprene emission has stabilized; T1 (ii) 3 min after changing CO2 to 78 Pa; T2 (iii) at 78 Pa CO2 after isoprene emission had stabilized; T3 (iv) 3 min after changing CO2 back to 39 Pa; T4 (v) at 39 Pa CO2 after isoprene emission has stabilized; T5. Each metabolite concentration is normalized to concentration of DXP. *Fig 4. The following variables were measured: (i) Isoprene emission (ii) Assimilation rates or photosynthesis (A) (iii) intercellular CO2 concentration (Ci), and (iv) stomatal conductance (gsw) at an interval of 5 s for 54 min. Treatments used: (i) H2O at 39 Pa CO2 (ii) H2O at 78 Pa CO2 (iii) H2O at 39 Pa CO2 (iv) ABA at 39 Pa CO2 (v) ABA at 78 Pa CO2 H2O: water, ABA: abscisic acid *Table 1. Isoprene emission and photosynthesis (A) measured at 25degC and 35degC at 39 Pa and 78 Pa CO2. Temperature coefficient (Q10) was measured for isoprene and photosynthesis at 39 Pa CO2 and 78 Pa CO2 using the formula: Q_10=(R2/R1)^((10/(T2T1))) *Fig S1A,B. Photosynthesis (A) and stomatal conductance (gsw) measured in 10 biological replicates at 39 Pa CO2 and 78 Pa CO2.
 Relative change: Difference in photosynthesis (A) and stomatal conductance (gsw) between 39 Pa and 78 Pa CO2 relative to their values at 39 Pa CO2, expressed in percent
 Mean: Mean of relative change in photosynthesis (A) and stomatal conductance (gsw) at 39 Pa and 78 Pa CO2
 SD: standard deviation
 pvalue: calculated by Student's ttest (2 tailed, paired) *Fig S2A,B,C,D. Relative change in photosynthesis and carbon cost of isoprene emission (I/A) under (i) light intensities of 1000 umol m2 s1, 750 umol m2 s1, 500 umol m2 s1, 250 umol m2 s1, and 100 umol m2 s1 in 3 biological replicates rep 1, rep 2, and rep 3 (ii) temperatures 25degC, 30degC, and 35degC in 6 biological replicates rep 1, rep 2, rep 3, rep 4, rep5, and rep 6. Mean: mean of biological replicates at each light intensity/temperature SD: standard deviation *Fig S4. Isoprene emission and stomatal conductance (gsw) under varying CO2. *Fig S5. Levels of hydrogen peroxide (H2O2) measured in 5 biological replicates (R1, R2, R3, R4, R5) at 39 Pa CO2 and 78 Pa CO2. Rep1, rep2, and rep 3 are technical replicates.
 Mean: Mean of technical replicates
 SD: standard deviation
 pvalue: calculated by Student's ttest (2 tailed, unequal variance) *Fig S6. Growth conditions (light and temperature) in the greenhouse for growing poplars. Daily light integral (DLI) was calculated by multiplying each value of light intensity in umol m2 s1 by 600 (since measurements were recorded every 600 s) then taking a sum of all the values over 24 h. Day temperature was calculated by taking a mean of temperature readings from 6:13 am to 9:53 pm Night temperature was calculated by taking a mean of temperature readings from 10:13 pm to 6:03 am
Methods
a. Data for isoprene emission was collected using the Fast Isoprene Sensor (FIS)
b. Measurements of photosynthesis (A), stomatal conductance (g_{sw}), intercellular CO_{2} (C_{i}) were conducted in a LICOR 6800.
c. Metabolite analysis was conducted on a Xevo TQXS mass spectrometer.